KV-4 Bykov. Illustration by Pavel ‘Carpaticus’ Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 heavy tank program was an ambitious development over previous heavy tank projects developed at the LKZ plant in Leningrad. Catalyzed by the rumors of German heavy tank developments, the KV-4 was to have thick 120 mm or more of armor and a powerful 107 mm gun. Almost two dozen different proposals were designed by the factory’s engineers, with various features and layouts. One of these was designed by Bykov, which featured two rotating turrets and a long, well-armored hull. Neither this nor any of the other KV-4 proposals left the drawing board, as the focus shifted towards developing the KV-5, and after the start of the invasion of the Soviet Union, these projects were scrapped.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
The KV-4 program had its origins in a pivotal letter dispatched by the Soviet Intelligence Services to the Soviet military on 11 March, 1941. This letter contained critical information concerning a formidable German heavy tank, boasting an impressive 90-tonne weight and armed with a formidable 105 mm gun. The revelation raised alarms within the Main Directorate of Armed Forces (GABTU), given that the heaviest tank in Soviet service at that time was the KV-1, weighing in at 45 tonnes and plagued by mechanical unreliability, rendering it entirely unsuitable for mass production. While the LKZ (Leningrad Kirov Factory), home to the SKB-2 design bureau responsible for the KV-1, had previously conceived heavier tanks, like the KV-220 and KV-3, these designs were still deemed inadequate to counter the suspected German heavy tank threat.
Consequently, on 21 March, the GABTU issued the original specifications for the KV-4 project. The tank was to weigh approximately 70 tonnes, armed with a 107 mm ZiS-6 gun in a turret and a 45 mm 20-K in a secondary turret. The powerplant designated was a potent 1,200 hp enhanced aviation diesel V-12 M-40. Armor requirements were set at 120 to 130 mm for the front, sides, and rear. The deadline for the complete blueprints was established as 17 July.
However, by 7 April, the requirements underwent another revision. The KV-3 was slated for resurrection with substantial improvements to its specifications. Consequently, the KV-4’s weight increased to 75 tonnes, with its armor bolstered to 135 mm. The deadline was also moved forward to 15 June. Notably, LKZ was also tasked with developing the KV-5, a massive 90-tonne tank sporting 150 to 170 mm of armor, while still being armed with the 107 mm ZiS-6 gun. It was expected to compete against the KV-4, with trials anticipated to commence in early 1942. In the interim, until one of these designs entered mass production, the KV-3 was to serve as a temporary solution.
The program’s Chief Designer was J.Y. Kotin, who, in light of the generous program requirements, adopted an unconventional approach to the design process. He initiated a competition among the engineers at SKB-2 and even offered financial incentives for the top seven best designs. One of these KV-4 designs was created by a certain Bykov, which was awarded 500 rubles for receiving 7th place.
The Designer – Bykov
Unfortunately, at the time of writing, there is no information about the designer of this KV-4 proposal, known so far only by the name Bykov, with unverified sources claiming “V. Bykov”. While there were several soldiers and tankers in the Soviet Army with this name, there is no way to tell if they match this designer. It was possible that an engineer would be sent to the front, especially if they had military training. One such example was SKB-2 engineer L.N. Pereverzev, who at the start of the war was transferred to a tank mobile repair battalion.
Another possibility is that “Bykov” was actually N.V. Barykov, an experienced SKB-2 engineer, and the text was incorrectly rewritten or damaged.
Design
The general layout of the tank was conventional, with the main turret in the center of the hull and powerplant in the rear. At the front, a secondary turret was added, on the right side of the hull. The main turret was mounted higher up than the secondary turret to allow for more internal space, as well as better clearance for the main gun. The running gear consisted of seven steel roadwheels per side, sprung by torsion bars. The idler was at the front.
The main turret had a rounded heptagonal shape, with the sides angled inwards. Although the blueprints do not provide much detail, a machine gun cupola with a rotating periscope was present. However, the blurriness of this cupola might suggest that it was removed in later design stages.
Directly underneath the main turret ring was the fighting compartment, 107 mm gun ammunition stowage racks, fuel tanks (on the floor), and part of the engine bay, which was separated by a firewall. The final drive and sprocket were in the very rear end of the hull, with the air cooling system above. To save space, the fuel tanks were modeled around the torsion bars running across the hull’s width.
Side cutout view of Bykov’s KV-4, showing the different components, such as engine compartment, ammunition stowage, and armament. Source: ASKM via Stalin’s Supertanks IS-7Transverse view of the hull, showing the fuel tanks and ammunition stowage for the 107 mm gun. Source: ASKM via Stalin’s Supertanks IS-7Top view of Bykov’s tank. Next to the secondary turret, the flamethrower and 45 mm gun ammunition stowage can be seen.
Crew
The crew of Bykov’s KV-4 consisted of 8 crewmembers: commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver, and bow machine gunner/radio operator.
The gunner was seated to the left side of the gun, with the commander likely behind him. The commander had a rotating cupola armed with a DS-39 machine gun. Unfortunately, the blueprints do not show enough detail, but it is likely that it was intended to mount several periscopes or vision slits, like on other KV-4 tanks. The main gun loaders would load the main gun, one operating the breech and the other lifting the shells from the hull stowage racks.
In the hull, the driver was positioned in the center, with a slight offset towards the left, to allow for additional space for the secondary turret to his right. The driver, aside from driving the tank, would also operate the flamethrower to his left. The bow machine gunner sat on the right side of the hull, in front of the secondary turret fighting compartment. He likely would have been in charge of operating the 10-R radio system. The secondary gunner and secondary loader sat inside the smaller turret to the left and right of the gun respectively, though oddly, the secondary ammunition was stowed on the right side of the hull, underneath the flamethrower.
Armor
The armor on Bykov’s KV-4 design maintained the typical required thicknesses. Frontal plates were 125 to 130 mm thick, while side and rear plates were 125 mm thick. Much of the design maintained the same angles and features as most other KV designs, such as the stepped frontal hull design and split rear hull plates for engine air cooling intake. The turrets were made out of pressed armor plates with a thickness of 125 mm. Hull and belly armor varied between 30 and 50 mm thick plates.
Armament
All KV-4 proposals were to be armed with the new 107 mm ZiS-6 gun developed at Plant No.92 as well as a variety of other weapons, including a 45 mm 20-K gun, several 7.62 machine guns and in some cases, even a flamethrower.
In Bykov’s design, the 107 mm gun was mounted in the main turret in the center of the chassis. This gun had excellent ballistic values, having a muzzle velocity of 800 m/s and penetrating 115 mm of armor from 1,000 m. The large, single piece shell weighed 18.8 kg and was 120 cm long.
The 45 mm 20-K gun was still the most prevalent gun within the Soviet armored forces and was still capable of dealing with a variety of lightly armored targets. It was placed in a secondary turret at the front of the hull. This gun had a muzzle velocity of 750 m/s.
For protection against infantry, Bykov’s KV-4 had a DS-39 7.62 mm machine gun in a ball mount in the front of the hull and one in a small rotating cupola, on top of the main turret. The tank also featured a flamethrower mounted in the left side of the frontal armor plate.
Fate and Conclusion
By 9 May, the competition concluded, and the winners were announced. In total, between 24 and 27 proposals were submitted, resulting in 11 prizes awarded to 13 designers, as some designs earned the same ranking, and a few designers collaborated.
The leading design was that created by N.L. Dukhov, which maintained a standard layout, largely influenced from the KV-220. Second place was initially awarded to a group of three engineers working together, resulting in a vehicle with the main gun enclosed in a casemate with the secondary turret on top. However, this design was later disqualified due to the fact that the original requirements meant that the KV-4 was to have the main gun in a fully rotating turret. Instead, what was originally third place was moved up to second and so forth. This design was by experienced engineer N.V. Tseits, who focused on making a very low-profile hull by enlarging the turret. Bykov’s design was one of the three engineers to be awarded third place, alongside Pereverzev and Kalivod.
After the competition, work on the KV-4 disappeared from the records. Instead attention was shifted to the KV-3 and KV-5, the latter which was based largely on design features of the KV-4 projects. Work on these two tanks would continue until 22 June 1941 when the Axis powers invaded the Soviet Union, work on the projects stagnated. Shortly after, between July and August, the staff of the SKB-2 design bureau were evacuated to the Chelyabinsk Tractor Plant (ChTZ), while the LKZ plant fully transferred towards the production and maintenance of KV-1 tanks. With the move, the super heavy tank KV-4 and KV-5 projects were abandoned, and never picked up again.
KV-4 Bykov. Illustration by Pavel ‘Carpaticus’ Alexe.
KV-4 Bykov Specifications
Dimensions (L-W-H)
9.5 x 4.03 x 3.65 m
Total weight, battle-ready
98.6 tonnes
Crew
8 (commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver and bow machine gunner/radio operator.
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
36 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
1 or 2 DS-39 machine guns
1 flamethrower
Armor
Front: 130 mm
Sides & rear: 125 mm
Top: 40 mm
Belly: 50 mm
The development of a completely new tank meant to replace the IS-2 began in summer 1943 at the ChKZ plant in absolute secrecy, with first models being shown to the state in December. After project approval and funding, further work commenced and a first prototype was built in April 1944 under the index Object 701 and prototype number ‘0’. A series of other prototypes were built thereafter until 1945, when the IS-3 had entered service and the tank was deemed unnecessary. A year later, due to issues with the IS-3 tank, the Object 701 program was revived and would enter service under the name IS-4.
Development
In July 1943, the SKB-2 heavy tank design bureau of the ChKZ (Chelyabinsk Kirov Plant) began the development of a new heavy tank out of its own initiative and funds. This was a few months prior to the IS-2 entering service, but even then, there were several known shortcomings of the tank, such as the stepped driver’s hatch, fuel tank position, and overall armor thickness.
Besides designers from SKB-2, engineers from the Bauman Moscow Technical University and Central Artillery Design Bureau (TsAKB) were called to work on the integration of the transmission and armament, respectively. Chief designer was the head of the bureau, N.L. Dukhov, while the chief engineer was C.N. Makhonin and the senior engineer was L.S. Troyanov, later replaced by M.F. Balzhi. The reasoning behind this project’s creation was that the military needed a well-armored heavy tank, immune to the German 75 mm and 88 mm guns found on the Panther and Tiger tanks.
The GABTU (Main Directorate of Armored Forces) would eventually recognize the need for a better armored heavy tank after deep analysis of the Battle of Kursk and combat performance of the IS-2. Thus, in November 1943, the requirements for a new heavy tank were laid down. It was to have a mass of 55 tonnes, frontal armor thickness ranging between 160 and 200 mm, 800 to 1,000 hp engine, main armament with caliber of either 122 mm or 152 mm, top speed of 35 km/h, and crew of 5 men.
By December, the first draft of the project was ready. A scale model was presented under the name K or K-1. Factory director I.M. Saltzman signed and approved the project on 10 December, and on the same day, the People’s Commissar of Tank Industry, V. A. Malyshev, approved the project and supplied funding from the state.
First draft model of the Object 701, named K or K-1. Source: Domestic Armored Vehicles 1941-1945
In the following months, the project advanced steadily, and by spring 1944, a second mock-up was built, simply called Object 701. Design and development was carried out by I.M. Zaltsman as director of the project, S.N. Makhonin was chief engineer, N.L. Dukhov as chief designer, and lead designer as L.S. Troyanov. After a commission created by the GABTU evaluated the project, a go-ahead was given for producing two prototypes of the Object 701 tank in as little time as possible. Compared to the previous K-1 model, the new mock-up featured an altered turret, with a better integrated gun mantlet, lower commander cupola, and dropping of the rear-facing machine gun.
Scale model of the Object 701, spring 1944. From this angle, several differences between it and the K-1 can be seen. Source: Domestic Armored Vehicles 1941-1945Front view of the Object 701 model. Source: Domestic Armored Vehicles 1941-1945Rear view of the Object 701 scale model, showing the stepped rear engine deck. Source: Domestic Armored Vehicles 1941-1945
A state resolution would confirm the GABTU’s will, and on 8 April 1944, Stalin signed decree No. 5583 giving the go-ahead for production of two prototypes, as well as one or two hulls for ballistic trials. The first of the Object 701 pilot tanks was given the index No.0. It was armed with an 122 mm S-34-II gun and equipped with the 750 hp V-12 engine. Its production began just two days later, on 10 April, and in two weeks, it was ready for factory trials.
Trials
The No.0 prototype was ready by late April and underwent factory trials between 10 and 24 April, during which it had traveled 1,230 km. In early June, to better test the reliability and functionality of the prototypes, the turret from prototype No.1 was installed on the hull of prototype No.0 and vice-versa. Trials of prototype No.0 ended on 15 June, 1944. Between 6 August to 3 October, ballistic trials of the S-34-II 122 mm on the prototype No.0 were held, passing the tests after firing 780 rounds.
Design
Despite being created with the intention of replacing the IS-2 as the new generation of Soviet heavy tank, the Object 701 had a vastly different upper hull, but maintained many of the same elements of the IS-2 chassis. The hull had been elongated, with seven roadwheels per side, completely redesigned upper hull, as well as new powerplant and armament.
The front of the hull consisted of a sloped upper frontal plate, splitting into a highly angled cheek plate on each side. A large bulge dominated the upper part of the frontal plate, which gave room for the driver’s head, as well as his direct vision port. Two additional periscopes were mounted on top of his service hatch, right underneath the gun. On the lower part of the frontal plate, two tow hooks were welded. The lower frontal plate was slightly angled inwards and had four spare track links attached. On the right cheek plate, the headlight and horn were mounted. The upper sides of the hull were slightly angled inwards and were covered by two external fuel tanks and a toolbox on each side.
Many chassis components were borrowed from the IS-2, including the roadwheels and idler, which were still rimmed and sprung by torsion bars. In contrast, the sprocket and return rollers were designed specifically for the Object 701.
Due to the lengthening of the hull, the rear of the engine compartment was redesigned compared to the IS-2. Instead of the large slope, a ‘step’ was added, separating the engine compartment from the final drive. A tow cable was mounted here, looping across the final drive deck. On top of the engine deck, four armored grilles protected the engine cooling fans, engine access hatch and three caps for internal fuel tanks. An additional hatch was provided for accessing the fuel filters, but was bolted down. The roof over the final drive and transmission was hinged for easier operation.
The turret maintained the rounded shape and cast construction of the IS-2, but presented new design elements. The front was no longer an elongated sphere, but had more defined cheeks, offering better frontal protection. The gun mantlet was tapered outwards, around the gun. A large bulge was cast in the right turret cheek to give room for the gun controls and aiming devices. Several handles were welded across the turret for riding infantry to hold on to.
The roof of the turret was separated into four plates, of which the center was bolted down to allow for the gun to be removed with relative ease. Two service hatches were provided, for the gunner and commander on the right side, and for the loader on the left.
Front view of the Object 701 No.0 during trials. Note the bulge on the right side of the turret cheek. Source: Soviet Heavy Tank IS-4Side view of the first Object 701 prototype, likely before trials, summer 1944. Source: Soviet Heavy Tank IS-4
Crew
The driver was seated in the hull and had two MK-4 fixed periscopes in the hatch on the hull roof, as well as a direct vision slit with armored glass. Besides his driving levers and pedals, he had a gauge panel, two compressed air cylinders for starting the engine and four 6STE-128 batteries. Behind him, in the floor of the hull, was an emergency escape hatch.
In the turret, the gunner was seated on the right side of the gun. For vision, the gunner was equipped with two MK-4 fixed periscopes and a rotating periscope. The turret could be traversed by the gunner using both manual and electric systems, with the rotation speed varying between 0.006 and 7.5º/sec when aiming, and 15º/sec when turning the turret at full speed. The gunner’s main sight was a TSh-17 telescopic sight, fixed to the gun. For vertical traverse, a distinctive cutout in the turret cheek armor was made. The electric trigger was placed directly on the vertical traverse control wheel.
The commander was seated behind the gunner and would operate the 10-RK radio station. For communication, the crew had a TPU-4 BIS-F intercom system. Right above him was the service hatch for him and the gunner.
The loader, situated on the left side of the gun, stood on the rotating turret basket floor. He also had a service hatch in the turret roof with a TK-4 periscope.
For personal defense, the crew had two PPSh submachine guns and 25 F-1 hand-grenades.
Cutout rear view of the first two Object 701 prototypes showing the fighting compartment, ammunition layout and armor thickness. Source: Domestic Armored Vehicles 1945-1965
Armament
The main armament consisted of the 122 mm S-34-II gun, developed at TsAKB during the same period as the Object 701, with similar ballistics to the 122 mm A-19 gun. Compared to the D-25T gun used on the IS-2, it had a better structural design and moreover lacked a muzzle brake, which decreased the horizontal blast, improving safety for nearby infantry. A bore fume evacuation system was also added, ejecting fumes when the rammer was opened, decreasing fumes in the fighting compartment and improving rate of fire. The horizontal gun sliding breech lock was semi-automatic. Another major change was the shift of the gunner’s position to the right of the tank, as opposed to the left, as most common on Soviet tanks of the era. The gun had an elevation of +19° and depression of -3°. The first prototype of the S-34-II gun was mounted on the Object 701 prototype No.0 and was tested on it.
The tank also featured a coaxial 7.62 mm DT machine gun, mounted on the left side of the gun, which could be fired by the gunner, but loaded by the loader, with 26 spare ammunition drums.
The two-part ammunition was scattered in the tank, with the projectiles stowed in the rear turret basket, and cartridges stowed in the hull sides, turret basket and left turret side wall.
Armor
Hull armor was 42SM armor steel of medium hardness, with the upper frontal plate being 120 mm thick and angled at 61° from vertical. The lower plate was 150 mm angled at 20° from vertical. Side armor was 160 mm thick, angled at 21° on the upper hull and flat on the lower hull. Rear armor was 120 mm thick. Deck and belly armor were 30 mm.
Turret armor was of cast type 66 of medium hardness. Front and rear varied between 160 to 200 mm and the sides were 170 mm, angled at 20°. The roof plates were 30 to 40 mm thick.
Powerplant
The engine compartment, situated in the rear of the hull, was separated from the central fighting compartment by a firewall. The engine was a V-12 diesel engine, outputting 750 hp and max rpm of 2,100 and developed in the autumn of 1943. It was based on the V-12IS engine and boosted using a supercharger from an AM-38 aviation engine. The original maximal rpm of the engine was 2,200, but this had to be decreased for increased reliability once mounted in the tank.
The planetary transmission, designed by the Bauman Moscow Technical School, featured six forward and 3 reverse gears with a 3-stage gearbox.
On the left side of the engine was the oil tank and a fuel tank, and on the right side, the other two fuel tanks. The four radiators and cooling fans were situated above the fuel and oil tanks and were isolated from the rest of the compartment to prevent dust from entering. This layout was largely borrowed from that used on the German Tiger and Panther tanks, although the components themselves were purposely built for the Object 701.
The V-12 engine was used on the Object 701 prototypes and even production IS-4. Source: Domestic Armored Vehicles 1945-1965
Following Prototypes
The following prototypes, No.1 and No.2, were produced between May and June 1944, and underwent factory trials in Chelyabinsk supervised by a GABTU commission starting on 27 June (for prototype No.1) and 8 July (for prototype No.2) and were finished by the end of July. The prototypes had small variations, primarily regarding the main armament. Prototype No.1 had a 122 mm S-34-II gun as well as a 50 mm S-11 mortar in the turret, while prototype No.2 had a 100 mm S-34-I gun. After the trials, the prototypes were dismantled.
Object 701 prototype No.1, summer 1944. Source: Soviet Heavy Tank IS-4
In autumn and winter 1944, prototypes No.3, No.4, and No.5 were built and tested. Prototype No.6 was built and tested in 1945, however by this point, the IS-3 had entered service and interest in the Object 701 disappeared. However, in spring 1946, due to the problems and shortcomings found on the IS-3, the Object 701 was revived, and Prototype No.6 entered service under the name IS-4.
One of the Object 701 prototype No.6 in 1945, equipped with the D-25T. The tank would enter production a year later with minor alterations, under the name IS-4. Source: Soviet Heavy Tank IS-4
Conclusion
The first Object 701 prototype, while just a proof-of-concept, kickstarted a chain reaction of several prototypes for the project, designed to test different aspects and features, from different armaments to new armor thicknesses. Due to the rapid development and production of new and improved pilot models, prototype No.0 was rapidly forgotten and scrapped. Despite the lengthy development period, the final product in the form of the IS-4 proved to be an obsolete vehicle, designed for a war which had ended several years prior.
Object 701 Prototype No.0. Illustrated by Pavel “Carpaticus” Alexe.
Object 701 Prototype No.0 Specifications
Dimensions (L-W-H)
6,600 – 3,260 – 2,450 mm
Total weight, battle-ready
55-56 tonnes
Crew
4 (Commander, gunner, loader, driver)
Propulsion
750 hp V-12 diesel at 2,100 rpm
Speed
35 – 40 km/h (hypothetical)
Armament
122 mm S-34-II
7.62 mm DT machine gun (coaxial)
Armor
UFP: 120 mm
LFP: 150 mm
Side hull: 160 mm
Rear hull; 120 mm
Deck & belly: 30 mm
Turret: 150 to 170 mm
No. Built
1
Sources
Soviet Heavy Tank IS-4 – Maxim Kolomiets
Stalin’s Superheavy tank IS-7 – Maxim Kolomiets
Domestic Armored Vehicles 1941-1945 – A. Solyakin, I. Zheltov, I. Pavlov, M. Pavlov
Domestic Armored Vehicles 1945-1965 – Ivan Pavlov, Mikhail Pavlov
IS Tank – Igor Zheltov, Alexander Sergeev, Ivan Pavlov, Mikhail Pavlov
Soviet Union (1943-1944)
Heavy Tank – Scale Model Built
In the summer of 1943, the Chelyabinsk Kirov Plant began the development of a new heavy tank out of their own initiative under the name K and index Object 701. By December, the drafts of the tank were presented to the state and further funding and development was approved. By March 1944, the project had evolved significantly and morphed into what is today the better known Object 701 design. The first prototypes of the newly drafted design were built in May. These would lead up to the creation of the IS-4 by 1946. As for the K tank, it remained just a model.
The IS-2 is largely celebrated as one of the most powerful tanks deployed in combat by the Soviet Union, whether it be propaganda, or rightfully through its technical prowess. Its thick, sloped armor made it immune to a variety of weapons fielded by the Axis forces, while the powerful 122 mm D-25T gun could defeat most German tanks. Yet, even before it entered service in October 1943, several concerns were brought up, especially regarding its protection.
IS-2 during testing at NIBT, January/February 1944. Note the 122 mm D-25T gun with the German-style muzzle brake.
Source: Warspot
In September 1943, Marshal of the Armed Forces Y.N. Fedorenko requested in a letter to Stalin that the IS receive thicker armor and its weight be increased to 55-60 tonnes. Truthfully, the German Panther’s 75 mm KwK 42 L/70 could penetrate its frontal armor, especially due to its ‘stepped’ shape, caused by the driver’s position, which presented a much flatter frontal target. This issue was further highlighted after analysis of the battle of Kursk, which saw both the Soviet and German sides field new and powerful vehicles.
As early as July 1943, out of its own initiative, the ChKZ (Chelyabinsk Kirov Plant) heavy tank design bureau SKB-2 began the development of a new heavy tank to replace the IS-2. Alongside its own engineers, SKB-2 would employ designers from the Bauman Moscow Technical University for the development of the transmission and ballistic engineers from for the armament. Chief designer was the head of the bureau, N.L. Dukhov, Chief engineer was C.N. Makhonin and Senior engineer was L.S. Troyanov, later replaced by M.F. Balzhi. The main goal was to create a strong new tank for the military by mainly focusing on its protection, which was to be capable of withstanding fire from both the German 75 and 88 mm guns on the Panther and Tiger. As the project was a factory initiative, its funding came from the plant’s own budget.
In November 1943, the GABTU (Main Directorate of Armored Forces) laid down the requirements for a new heavy tank. It was to have a mass of 55 tonnes, 5 crewmen, 160 to 200 mm of frontal armor, an 800 – 1,000 hp engine, main armament of caliber 122 or 152 mm and top speed of 35 km/h. These requirements were signed by ChKZ factory director I.M. Saltzman on 3 December.
With these new requirements in mind, the new ChKZ heavy tank first draft was ready and signed by Saltzman on 10 December, under the name “K” (likely from Kirovets) and index Object 701. On the same day, the tank was presented to the People’s Commissar of Tank Industry V. A. Malyshev, who approved the project and gave additional funding. A scale model of the K tank was made, showing its unique features and a large step forward from the IS-2. Unfortunately, the blueprints were reused for other purposes in 1944 and then scrapped.
The model of the K tank, showing the vast design improvements in respect to protection compared to the IS-2.
Source: Domestic Armored Vehicles 1941-1945
Development of the Object 701 continued and a second model was presented. It was very similar to the original K tank, however, several features were changed, such as removing the muzzle brake, rear ball-mounted machine gun and altered gun mantlet. It is on this design that the first Object 701 prototype (No.0) would largely be based.
The Object 701 model, spring 1944. It was largely based on the K model presented in December 1943.
Source: Domestic Armored Vehicles 1941-1945
Design
The K tank was revolutionary in terms of armor layout and profile. The hull was completely redesigned, with the front being divided into three segments, with the main upper plate being heavily angled. The rounded cheeks found on the IS-2 were replaced with steeply angled plates as well. The entire hull was lengthened, adding an extra roadwheel. In the engine bay, a “step” was added between the engine deck and lower hull, which allowed for the extension of the track length without excessively increasing the volume and mass. Instead of a large grille, engine cooling was provided by two large fans with circular cutouts on the engine deck. A large hatch for servicing the engine was provided. The steel roadwheels were sprung by torsion bars and the track was supported by three return rollers. The sprocket and final drive were kept in the rear of the hull.
The turret was hexagonal shaped, with no flat surfaces, but rather various curves were implemented. The flatspot of the rounded IS-2 turret cheeks was removed by introducing a greater angle and by using a larger mantlet. The height was also reduced, with an extension of the turret roof to allow for higher gun depression values. A rotating periscope was mounted on the roof to be used by the gunner. The commander also received a cupola with a single rotating periscope. In the rear of the turret, the ball-mounted machine gun was kept.
Front view of the K tank. The frontal hull was completely redesigned, and the angled plates can be seen.
Source: Domestic Armored Vehicles 1941-1945 Rear view of the K tank, showing the redesigned engine roof area and rear hull. This “step” format would be kept even on the production IS-4.
Source: Domestic Armored Vehicles 1941-1945 Bottom view of the K tank model.
Source: русская-сила.рф
Crew
The crew layout remained largely the same as on the previous IS tanks, with 4 men. The crew consisted of a commander, gunner, loader, and driver.
The gunner was seated to the left of the main gun, with the commander behind him. The commander had a cupola with a service hatch and periscope. He was also responsible for operating the 7.62 mm DT machine gun in the turret rear wall, behind him. The loader was standing on the opposite side of the commander, to the left of the gun.
The driver sat in the hull, directly underneath the main gun. He had one periscope for vision and a service hatch, which could have posed issues in case of an emergency exit, as the gun could prevent the hatch from opening or the driver from exiting. Thus, an internal emergency hatch would have likely been placed behind his seat, as commonly found on other Soviet tanks of the time.
Armor
The front of the hull was to be 160 mm thick on the upper plates and 120 mm thick on the lower plates. The side armor was 160 mm thick on the upper hull and 150 mm on the lower hull. Rear armor plates were 120 mm thick. The turret was made out of cast steel and was 150 mm thick all around. The effective thickness was increased thanks to the angling.
Armament
The main armament would have been the same as on the IS-2, the 122 mm D-25T with two-part ammunition. The only apparent change was the replacement of the muzzle brake with a German-style one, developed after studies on German tank guns. The gun had a muzzle velocity between 790 m/s and fired armor-piercing BR-471 and high-explosive OF-471 shells. In the late stage of the war, a new AP round was fielded, the BR-471B. The amount of ammunition carried onboard is unknown.
D-25T Ammunition characteristics
Type & Name
Weight
Explosive charge
Penetration (1,000 m at 90 ° )
AP BR-471
25 kg
156 g TNT
143 mm
AP BR-471B
25 kg
?
142 mm
HE OF-471
25 kg
3 kg TNT
N/A
Source: Encyclopedia of Russian Artillery – A.B. Shirokorad
Diagram showing the D-25T mount in the IS-2 with the German-style muzzle brake. Note that the barrel was shortened on purpose.
Source: Amizaur via Battlefront.com
It is also entirely possible that the K tank was to be fitted with an 122 mm S-34 from TsAKB, hence why artillery specialists from that bureau took part in the tank’s armament integration. This gun would be used on the second Object 701 draft and first few prototypes. Its main characteristic was the lack of a muzzle brake.
Powerplant
Despite the fact that the K tank was to be powered by an 800 to 850 hp engine, there were no working models at the time. Only later, in 1944, did plant No.76 design the V-14 with 800 hp output. A replacement for the Object 701 engine was the V-12 diesel engine, with 750 hp at 2,100 rpm. It was designed at the ChKZ beginning in February 1943 and was equipped with a centrifugal turbocharger from the AM-38 aviation engine.
The V-12 engine used on the K tank and its later Object 701 prototypes and even IS-4.
Source: Domestic Armored Vehicles 1945-1965
Later Object 701 prototypes and IS-4
On 8 April 1944, the ChKZ plant was given permission to build two prototypes of the new heavy tank and a ballistic hull testbed, which kept the index Object 701. Additionally, the ChKZ was also tasked with the development of an IS-2 upgrade. Chief designer was N.L. Dukhov and Chief engineer was M.F. Balzhi. In a meeting held on 4 May, the goal of the IS-2 upgrade tank was to strengthen its armor protection, reduce the fire hazard from fuel tanks in the engine compartment, as well as improve accuracy and rate of fire. However, work on this upgrade progressed very slowly due to the ChKZ plant heavily focusing on the Object 701 instead. The first prototype of the Object 701 was built in April, receiving index Object 701 No.0, followed by Object 701 No.1. After seven prototypes and rigorous testing in spring 1945, the Object 701 would enter service only on 29 April 1946 under the name IS-4.
The Object 701 No.0, built in April 1944. The similarities to the Object 701 model and in turn, the K model, are clear.
Source: Soviet Heavy Tank IS-4
The mysterious K-2
In the book by Russian historian Maxim Kolomiets, Soviet Heavy Tank IS-4 (2014), he presents the K tank as part of the IS-4’s development. In 2013, blogger Peter Samsonov made the same correlation in one of his blog posts. However, the tank model shown as proof is largely different to the K-1, using a different turret, as well as an entirely new frontal hull. Other changes include the service light and return roller position. This seemingly was a further development of the K tank, hence its popular online index “K-2”. Although, considering the similarities between the K tank model and the later Object 701 model, the “K-2” does not fit in the timeline. Rather, based on its design, it could have been a model for later Object 701 developments or early Object 703 design ideas, placing it somewhere between summer and winter 1944. In his newer book, Soviet Heavy Tank IS-4 (2019), Kolomiets replaced the photos of the “K-2” with one of the actual K tank.
The mysterious K-2 tank, often regarded as a further development of the K (Object 701). However, due to its radical changes, it is much more likely that it was a further development of the Kirovets-1, and predecessor to the IS-3.
Source: Soviet Heavy Tank IS-4
Conclusion
The K-1 tank featured a lengthened hull, thick, angled armor plates and new turret significantly improved the survivability of the tank compared to the IS-2. It was a pivotal step in the development of the Object 701, which would enter service with the Soviet armed forces in 1946 as the IS-4.
K tank illustrated by Pavel Alexe
K-1 (Object 701 first draft) Specifications
Dimensions (L-W-H)
6,520 – 3,220 – 2,360 mm
Total weight, battle-ready
56 tonnes
Crew
4 (Commander, gunner, loader, driver)
Propulsion
750 hp V-12 diesel at 2,100 rpm
Speed
35 – 40 km/h (hypothetical)
Armament
122 mm D-25T alt. 122 mm S-34
2x 7.62 mm DT machine gun
Armor
UFP: 160 mm
LFP: 120 mm
Upper side hull: 160 mm
Lower side hull: 150 mm
Rear hull; 120 mm
Turret: 150 mm all around
KV-4 Grigoriev & Pavlov). Illustration by Pavel ‘Carpaticus’ Alexe
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
At the start of 1941, the Soviet Union’s heavy tank fleet consisted of the KV-1, which had its share of problems, including poor mobility and mechanical unreliability, and the hopelessly obsolete T-35A. To address these shortcomings, work had already begun in 1940 on creating a heavier and better-armored KV-1, leading to designs like the T-150, KV-220, and Object 222.
However, in March 1941, two reports would drastically change the course of Soviet heavy tank development. Firstly, the testing of German anti-aircraft guns of calibers 88 mm and 105 mm concluded that future Soviet heavy tanks would need at least 130 mm of armor to withstand incoming fire from these guns. Secondly, and likely more importantly, reports on German heavy tank developments were presented to the Soviet officials. The most unnerving of these tanks was the Pz.Kpfw.VIII, which was to weigh 90 tonnes and be armed with a 105 mm gun.
On March 21, 1941, the Main Directorate of Armed Forces (GABTU) issued requirements for the development of the KV-4 (Object 224), specifying a 70 to 72-tonne heavy tank armed with a 107 mm ZiS-6 gun in the turret, a secondary 45 mm 20-K gun, and at least three DT machine guns. The armor was to be 130 mm thick at the front and 120 mm on the sides and rear, with a powerful 1,200 hp M-40 engine to provide propulsion, and a six-man crew. The deadline for the tank design was set for July 17, with prototype building and armament testing scheduled for October.
However, on April 7, 1941, the GABTU revised its requirements for the KV-4. The weight was increased to 75 tonnes, and the armor thickness was raised to 135 mm at the front and 125 mm on the sides and rear. The deadline for blueprints was tightened to June 15. At the same time, the GABTU requested an even heavier tank, the KV-5, weighing at least 90 tonnes with 170 mm frontal armor and 150 mm on the sides, to be developed alongside the KV-4, as well as the KV-3 (Object 223), also armed with the same gun, but with only 120 mm of frontal armor and weighing 68 tonnes.
The Leningrad Kirov Plant (LKZ), with its SKB-2 design bureau, began work on the KV-4 on April 10, 1941, under the leadership of J. Y. Kotin. In an unusual approach, Kotin organized a competition among the SKB-2 engineers to encourage innovation in the tank’s design. Over 20 engineers submitted more than 20 individual designs. The winning design, created by N. L. Dukhov, resembled an enlarged KV-220. Second place went to a design by K. I. Kuzmin, P. S. Tarotko, and V. I. Tarapatin, featuring the main gun in the hull and a secondary gun in a small turret. Third place was awarded to N. V. Tseits, who proposed a tank with a low hull and a large turret to compensate for limited hull space. One of the designs was submitted by a duo of designers, Grigoriev and Pavlov, however, their project was not rewarded in the competition.
Designers Grigoriev & Pavlov
Unfortunately, not much is available about the two designers of this tank. Based on the little information available, both were likely young, recent graduates from the Leningrad Technical Institute. D.E. Grigoriev’s first work at LKZ was on a mine plower, designing and building it using various methods of mine deactivation. For his work, Grigoriev would be amongst three SKB-2 engineers to receive the medal ‘For Labor Valor’. It is uncertain who D. G. Pavlov was, since his name is only mentioned by author Maxim Kolomiets in this context. Additionally, it most likely was not Soviet Army General D.G. Pavlov. Another possibility is that Kolomiets made a mistake, and that the person was actually B.P. Pavlov, a recent graduate student from the Military Academy of Mechanization and Motorization of the Red Army, who had worked on the layout and design of the KV-1, and was deputy designer of the KV-220 (later chief designer) as well as senior engineer of the KV-3 at the ChTZ.
Despite there being over 20 KV-4 designs, the one presented by the Pavlov and Grigoriev duo was one of the more unorthodox. The main turret was placed at the rear of the hull, while the powerplant was moved towards the front. At the bow of the hull, the final drive and engine air intake were placed. The driver’s position was in the center of the hull, in front of the fighting compartment but behind the engine, which was separated by a firewall. To his right was the secondary turret, which had limited traverse due to the protrusion in the upper hull for the driver’s position. The upper frontal plate of the hull was heavily angled, while the lower plate was curved, as opposed to flat on most KV tanks. The main turret had a large, hexagonal shape, with no particular details drawn in the blueprints. The fuel tanks were in the rear of the hull. Ammunition was stored horizontally, stacked underneath the turret ring.
One of the blueprints of the Grigoriev and Pavlov KV-4 design. Source: ASKM via Stalin’s Supertanks IS-7Second blueprint presented by the duo. Note the placement of the secondary turret, on the extreme right side of the hull, with an overhang over the tracks. Source: ASKM via Stalin’s Supertanks IS-7
Crew
The crew consisted of 6 men, commander, main gunner, main loader, secondary gunner, secondary loader, and driver. The gunner was seated to the left side of the gun, while the commander was seated behind him. Unfortunately, there are no additional details available, such as what equipment they had, aside that the commander likely operated the 10-R radio. The right side of the gun housed the main loader, which had the task of lifting the shells from the hull into the gun breech.
In the secondary turret were the secondary gunner and loader. They shared a single service hatch in the roof of the secondary turret. They were separated from the rest of the crew.
Lastly, the driver’s position was on the left side of the hull, in front of the fighting compartment. Directly to his left was a flamethrower, which he likely had to operate.
Armament
The 107 mm ZiS-6 was the main armament of all KV-4 tanks. It was developed at Plant No.92 by V.G. Grabin in a very short time. Due to its excellent penetration capabilities, it would equip all of the new Soviet super heavy tanks. In the summer of 1941, the gun was tested on a KV-2, using a KV-3 gun mantlet. There, the excellent power was proven, being able to penetrate 120 mm of armor angled at 30° from 1,600 meters. A total of 120 rounds were stowed in the hull for this gun.
The secondary gun was the 45 mm 20-K gun, which was the most numerous gun on Soviet tanks at the time. Although it was obsolete on a 1941 design, it was still a capable gun for soft-skin targets. The 170 ammunition shells were stowed behind the turret, on the hull floor.
As the Soviets mounted coaxial guns to the right of the main weapon, the KV-4 designed by Grigoriev and Pavlov was equipped with two machine guns (either DT or DS-39 models) with 4,000 spare ammunition. Additionally, a flamethrower was present as well, a weapon which a few other KV-4 designs featured. However, it was mounted to the left of the driver, meaning only he could operate it, and because his position was so far back, with the engine right in front, this could have been a serious fire hazard, as well as reducing the flamethrower’s effective range. The flamethrower had 150 liters of fuel.
The KV-2 used during the ZiS-6 gun trials, mounted with a KV-3 mantlet, June 1941. Source: Warspot
Powerplant
All KV-4 tanks were to use the aviation diesel M-40 engine with four TK-88 turbochargers, outputting 1,200 hp. This engine had also been developed at LKZ a few months prior. The top speed was to be 40 km/h, though that was slightly optimistic.
The M-40 aviation engine. Note the two TK-88 turbochargers. Source: Yuri Pasholok
Fate
After the winners of the competition were announced, work on the KV-4 program halted, focus shifting to the KV-3 and KV-5. However, with the start of the war on 22 June 1941, and the bleak situation on the front, these heavy tanks were further pushed back and delayed. The KV-4 and KV-5 were ultimately canceled in mid-July, when a large portion of the SKB-2 design bureau was evacuated from Leningrad to Chelyabinsk, at the ChTZ, due to the approaching German forces.
Conclusion
The ever-changing specifications, tight deadlines, and sheer complexity of the design process, including in a competition among engineers, made the KV-4 a short-lived but interesting project. Kotin’s idea of starting a design competition led to a range of innovative designs. This dynamic period in tank development reflects the urgency and adaptability of Soviet efforts to counter the threat of the perceived German super-heavy tanks, but also the wrong direction which Soviet tank design was taking. With the start of the war and cancellation of most heavy tank projects, focus went to improving existing tanks, as well as using trialed designs. This is how the KV-1S was born, and while far from perfect, it was arguably the best Soviet heavy tank at the time, especially considering the often-ignored fact that it worked.
KV-4 Grigoriev & Pavlov). Illustration by Pavel ‘Carpaticus’ Alexe
KV-4 Grigoriev & Pavlov Specifications
Dimensions (L-W-H) (approx.)
8.5 x 4 x 3.6 m
Total weight, battle-ready
91 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2x DT machine guns
1 flamethrower
Armor
Front: 125 mm
Front UFP: 100 mm
Sides & rear: 125 mm
Top: 40 mm
Belly: 50 mm
KV-3 (Object 223). Illustration by Pavel ‘Carpaticus’ Alexe
Soviet Union (1941)
Heavy Tank – 1 Partial Prototype + 1 Mock-Up Built
Right after the trials of the T-150 and KV-220 heavy tanks, trial reports on the anti-tank capabilities of high caliber German anti-aircraft guns and German heavy tank developments kickstarted the development of even more powerful heavy tanks. One of these was the KV-3, which used a slightly modified version of the KV-220 hull, but with an all new turret, armed with the new, powerful 107 mm ZiS-6 gun. Despite these features, several delays regarding the production of the first prototype and the invasion of the Soviet Union halted the progress to the point that the project was no longer needed.
The KV-220
The KV-1 entered production in the summer of 1941 at the Leningrad Kirov Plant (LKZ). In parallel, the plant was tasked with further developing the KV-1 to fit larger guns and thicker armor. The products were the T-150, T-220 and T-221. While the first was essentially a KV-1 with 90 mm of armor, the latter two featured new, lengthened hulls. The T-220, also known as the KV-220, had 100 mm of armor and was equipped with an 85 mm F-30 gun. The first prototype was completed on 7 December 1940, and tested in January the following year.
The SKB-2 design bureau, where the KV tanks were developed, had juggled with the idea of installing a 107 mm gun in a tank since August 1940. Engineer G.N. Moskvin was tasked with researching the fitting of a 107 mm gun inside the KV-220 turret. The gun would turn out to be the 107 mm F-42, developed by December of the same year, and later indexed ZiS-6.
The KV-220 tank on which the KV-3 was heavily based upon.
Source: Stalin’s Heavy Tank IS-7
Initial calculations revealed that fitting the F-42 gun in the KV-220 turret would have been nearly impossible, the cramped room and very long shells would have made loading impossible and the idea was dropped. The 107 mm gun reappeared in the picture when preparing the second KV-220 prototype. On 19 February, Marshal Kulik, overseeing work at LKZ, wrote a letter where he claimed that the second prototype was to be armed with the ZiS-6. However, physical work on this prototype did not start until June 1941.
Overlay of the 107 mm ZiS-6 (F-42) on the KV-220. Also note the difference in size between the 107 mm and 85 mm shell.
German Threats
The trials of both the KV-150 and KV-220 ended in late January due to serious engine failures, causing both tanks’ development process to be halted until Plant No.75 fixed their engines. The completion of the KV-220 was further delayed when, on 11 March 1941, the Soviet intelligence services sent a letter discussing German tank development. Most importantly, three German tanks were claimed to be under development, the 36-tonne Ausf.V armed with a 75 mm gun and 60 mm of armor, the 45-tonne Ausf.VI armed with a 75 mm gun and 70 mm armor and finally, the 90-tonne Ausf.VII with a 105 mm gun.
At the time, the only heavy tanks which the Soviets had in service were the horrendously obsolete T-35A and the new KV-1, which was apparently no match for the supposed super heavy German tank. Even the heavy tanks under development were no match. The T-150 had been canceled after the failed trials and replaced by the Object 222, essentially the same tank with a more streamlined turret and armed with the 76 mm F-34. This was also the first tank to be called KV-3. Additionally, the KV-220, while promising, still was not powerful enough to face the 90 tonne German tank.
Another issue which catalyzed the development of heavier tanks came from the trials of German 88 and 105 mm anti-aircraft guns by the Soviets, concluding that tanks needed 130 mm or more of armor that was specially treated at high-frequencies.
Thus, on 21 March, the Soviet GABTU (Main Directorate of Armored Forces) laid down the requirements for SKB-2 to develop a 72 tonne tank, armed with the ZiS-6 gun, which was called the KV-4, later given index Object 224.
On 26 March, 1st Rank Military Engineer Afonin sent a report to the GABTU regarding armor thickness and the issues caused by German anti-aircraft guns, leading the GABTU to cancel the Object 222, which was deemed inadequately armored.
The Object 222 was the first tank to be named KV-3. However, this index would later be given to the Object 223, with the 222 being re-indexed KV-6.
Source: Yuri Pasholok, edited
Shortly after, on 7 April, the Council of People’s Commissars of the Soviet Union requested two additional tanks. One was to be the new KV-3 (the Object 222 was thus renamed to KV-6), weighing 68 tonnes, and the other the KV-5, weighing 100 tonnes. Much like the KV-4, both of these tanks were to be armed with the same 107 mm ZiS-6 gun.
Just two days later, on 9 April, the People’s Commissariat of Heavy Machinery expanded on the previous decree, and the technical requirements were laid down. The frontal armor was to be 115-120 mm thick, turret armor 115 mm, and be equipped with the 107 mm ZiS-6 gun with 800 m/s muzzle velocity. Deadlines were also extremely tight. By 15 April, the drawings had to be ready and submitted to the Izhora plant. The first turret mock-up was meant to be ready by 25 April and the first full prototype by 20 May.
It is important to note that, while 120 mm of armor was less than the estimate of 130 mm to withstand the future German tank guns, it was deemed enough to protect against the 88 mm gun. Instead, the KV-4 had its frontal armor thickness set to 130 mm and the KV-5 to 170 mm.
Development
The KV-3 received index Object 223, and was to use the slightly altered hull of the KV-220 in order to simplify and speed up development. The only difference was that the frontal armor had to be thickened to 115 mm and a new turret had to be developed to accommodate the larger gun, as well as fitting 120 mm of frontal armor. The powerplant was meant to be the same 850 hp V-2SN supercharged diesel as on the KV-220. Work on the tank began in mid-April at SKB-2, with the chief engineer being L.E. Sychev, who was later replaced by B.P. Pavlov, though some sources contradict whether this swap was made when designing the KV-220 or KV-3. Work on the first mock-up used the hull of the T-221, work on which had begun earlier in February. Essentially an identical hull to that of the KV-220, the only change was the thickening of the frontal armor plates by 15 mm, to a total of 115 mm.
However, due to the problems of the V-2SN engine highlighted at the KV-220 trials, and until it was ready for production, the KV-3 would use a V-5, 700 hp engine. An experiment was made by loading the KV-220 hull up to a total mass of 70 tonnes and using the V-5 engine. The torsion bars were sagging by 2-3 cm, and between 12-15 April, the vehicle drove 150 km. Although the V-5 was deemed satisfactory on roads, on rough terrain, the tank could only be driven in 2nd gear. Another issue spotted with the engine was that it would eject hot oil through the cooling grille.
On 18 April, 2nd Rank Military Engineer Bubyakin reported to the GABTU that the KV-3 mock-up would be based on the T-221 hull and that there were plans to strengthen the side armor depending on the circumstances. By 26 April, the KV-3 mock-up was ready and, on 7 May, an inspection was made by a state commission, consisting of representatives from GABTU, People’s Commissariat of Heavy Engineering and LKZ. Several comments were submitted and changes had to be made. The bow 7.62 mm DT machine gun was recommended to be replaced with a flamethrower on some units. Other changes mostly involved the ZiS-6 gun. An internal travel lock, a gun rammer and single-piece ammunition were requested. Several structural and design changes were also proposed, especially regarding the turret.
View of the KV-3 mock-up, based on the T-221 hull. Note that this early variant has a DT machine gun in the front of the hull.
Source: Warspot
When it came to building the first prototype, several problems delayed the project. On 13 May, senior representative of the GABTU, Military Engineer 2nd Rank Dmitrusenko, claimed that the Izhora plant would, ideally, manufacture the stamped turret by 20 May. However, for this process, two dies and two punches were needed, but as of that day, the second die was still to be cast. Additionally, none of these components were heat treated and machined, which would have taken a few extra days. In his own words, Dmitrusenko wrote:
“There is a chance that by 20 May, the dies and punches will not be ready, let alone the turret itself. Unless the Izhora plant takes the most swift action in the coming days, the first turret will be manufactured no earlier than 15-20 June, exactly one month’s delay”
On 30 May, Dmitrusenko reported that the punches were being heat-treated in Shop No.15 and that the turret would be further delayed by a month.
Side collage of the KV-3 mock-up. The ‘bulge’ in the side turret armor for the commander and his cupola can be seen.
Source: Warspot View of the KV-3 mock-up, this time showing the rear of the hull and turret.
Source: Warspot
Further trials were made on 25 May using the loaded KV-220 (reaching 65-70 tonnes) hull and V-5 engine, this time traveling 410 km. Several issues were noted, including that the axles of the return rollers were bent, idler hubs were cracked and shock absorbers on some suspension arms were sheared. While, once again, the 700 hp engine was deemed to be capable of propelling the tank at a satisfactory speed of 35 km/h, its fuel range was not considered adequate.
A delivery contract was signed on 5 June 1941, where the LKZ plant would produce 500 KV-3 tanks in the remaining months of 1941, with the first 55 units to be delivered in August, 105 in September, 110 units in October and November and lastly, 120 tanks in December.
On 27 May, the LKZ plant received a ZiS-6 gun from Plant No.92 to test the gun inside a tank. Since none of the super heavy KVs meant to equip it was ready, a KV-2 was used for firing trials instead. The gun would be mounted in the KV-2 using a KV-3 gun mantlet and mount. However, the Izhora plant once again failed to deliver the KV-3 components on time, leading to Marshal Kulik having to send a letter requesting for a speed up of the process on 18 June. By 25 June, the tank was at the Gorokhovets proving grounds, where 618 shots were fired. While penetration was deemed excellent, the gun rammer broke after 315 shots and accuracy was compromised after 486 shots. Despite these problems, the ZiS-6 was deemed satisfactory, and the gun used during the trials was sent back to Plant No.92 for repairs. By this point, the armaments plant already had 214 guns in various stages of production.
A letter from a GABTU representative at LKZ from 20 July claimed that the KV-3 prototype was still not ready and that it was expected that there would be several major issues which would be complex to solve.
By this point, the KV-3 project was getting expensive. In a letter from the head of production at LKZ, A.I. Lantsberg, the development costs estimate of the various ongoing projects at LKZ was reported.
Development cost of the KV-3 (Object 223) [in руб]
Drafts and blueprints
100,000
Models and mock-up
50,000
Technical and functional drawings
350,000
Prototype construction and factory trials
1,300,000*
Military trials
150,000*
Drawing fixes/bug fixes
100,000*
Prototype bug fixes and repairs
450,000*
Sum
2,500,000
* note that the project never reached these stages, thus the project could have exceeded these allocated sums.
Start of the War
On 22 June 1941, the Axis forces began their invasion of the Soviet Union. This had an indirect effect on the heavy tank developments, as a lot of the resources had to be transferred to KV-1 production and repair. Nonetheless, work on the KV-3 and its heavier counterparts continued and several components of the first turret were finished, as well as the majority of the hull. However due to the war situation, between 26 and 30 June, an order was signed to transfer the development of the KV-3 tank to the Chelyabinsk Tractor Plant (ChTZ), alongside many of the designers. By mid-July, the KV-3 hull and other components were loaded on two rail platforms and sent from Leningrad to Chelyabisnk, with the turret being sent a little later.
On 26 July, the first of SKB-2 engineers started to arrive at ChTZ. The reasoning behind this evacuation was that the German forces were approaching the city of Leningrad. During this transfer, between July and August, the heavy KV-4 and KV-5 tanks were canceled, and work on them would not resume at ChTZ. The SKB-2 engineers in charge of the KV-3 at ChTZ were N.V. Tseits (chief engineer), B.P. Pavlov (senior engineer), G.F. Burkhanov, Merenkov, Petukh, Skortsov, Sobolev, A.S. Schneidman and N.F. Shashmurin.
Despite the fact that the KV-3 was not outright canceled, it still suffered from the transfer. Firstly, with the Siege of Leningrad beginning in September, all KV-1 production was also moved to ChTZ, leaving little resources for experimental tank work. This led to the KV-3 only appearing on various reports, letters and documents in the latter stages of 1941. Documents from September reveal that it was proposed by Plant No.92 to rearm the KV-3 with the ZiS-6A, essentially just the ZiS-6 with a 45 mm 20-K gun integrated within its system, much like on some KV-4 designs. This seems to have been more an attempt from Plant No.92 to not let their work on the ZiS-6 go to waste. Another document shows that the heavy bunker buster project, the Object 212, which was initially to be based on the KV-220, was to be built upon the KV-3 instead. On 22 December 1941, as part of the 1942 ChKZ (at the end of 1941, ChTZ was renamed to Chelyabinsk Kirov Plant) production and development plan, the KV-3 was mentioned as being in the works, with a deadline set to 1 May, 1942. Several aspects of the tank had also been reworked. By July, it was supposed to be equipped with an electrical transmission and, by December 1942, to be fitted with a 1,200 hp V-2 engine variant.
This was the last mention of the KV-3. By this point, the Soviet armored forces had suffered terrible defeats against the Axis, and were shifting focus in terms of tank design. The superior reliability and maneuverability of the T-34 caused the heavy tank industry to shift away from super heavy tanks and into the exact opposite direction, the KV-1S. With less armor than the KV-1, but with redesigned mechanical components and superior maneuverability, it was arguably the first successful Soviet heavy tank, at least from a mechanical perspective.
Design
As the tank was based on the KV-220 hull, much of the same aspects were kept. The hull was similar to that of the KV-1, but enlarged to seven roadwheels per side, sprung by torsion bars and four return rollers. The engine and final drive were in the rear, with the sprocket. The idler was in the front. One of the main differences in the hull, aside from armor thickness, was that the engine deck was angled downwards, compared to being flat on the KV-220.
Side cutout view of the KV-3, showing various elements of the tank. Note that this drawing is of the variant with the flamethrower.
Source: Yuri Pasholok, edited Side view of the hull’s plates with individual connecting pins and welds. Drawing was signed 16 April.
Source: ASKM via Stalin’s Supertanks IS-7 Top view of the hull and engine deck with several connections. Drawing was signed 16 April.
Source: ASKM via Stalin’s Supertanks IS-7 Cross view of the hull and its connections. Drawing was signed 20 April.
Source: ASKM via Stalin’s Supertanks IS-7 Cross view of the return roller on the KV-3. Drawing was signed 16 April.
Source: ASKM via Stalin’s Supertanks IS-7 Cross view of the torsion bar (note that they are cut), swing arms and roadwheels. Drawing was signed 22 April.
Source: ASKM via Stalin’s Supertanks IS-7
Turret
The biggest change with the new KV-3 was the new, stamped turret. Its shape was a rectangular pyramid with rounded edges. The side walls were angled at 30 degrees and extended over the hull side wall, requiring reinforcements in the hull. In the front, the large gun mantlet would house the gun and its elevation mechanism. A small protrusion was made in the left side of the turret wall to give more space for the commander and the cupola, which had six periscopes for vision. A vision port was added in the sidewall on the left side for the gunner, though it is possible that it was mirrored on the right side. In total, three firing ports were added on every side of the turret walls for firing the crew’s personal defense PPSh submachine guns. The turret ring size was 1,670 m. A service hatch was placed in the left side of the hull for use by the driver and radio operator, as well as an escape hatch in the hull floor, behind the driver’s seat.
The construction of the turret proved to be very problematic for the Izhora plant, the section of LKZ tasked with tank production. Stamped pieces of armor at 100 mm and above were a very difficult task to achieve, especially with the difficult shapes which the turret had. However, the design was a theoretical improvement over the boxy KV turret designs which the SKB-2 design bureau had made previously. In the coming years, Soviet military industrialists managed to achieve such complex armor plate shapes via casting.
Top view of the KV-3 turret, showing the armor thickness and gun mount. Note the coaxial DT machine gun.
Source: Yuri Pasholok, edited Rear view of the KV-3 turret showing the sharp angled of the side armor, as well as the gun breech and recoil mechanism.
Source: Yuri Pasholok, edited Internal and side view of the gun mantlet meant to mount the ZiS-6 gun.
Source: Yuri Pasholok, edited External view of the gun mantlet of the KV-3. This was the same mantlet as the one used on the KV-2 107 mm ZiS-6 testbed. Drawing was signed 29 April.
Crew
The crew consisted of 6 men, namely the commander, gunner, 2x loaders, driver and radio operator. The gunner sat to the left of the gun, in the left-forward corner of the turret. The commander sat behind him, and had a large cupola for viewing the battlefield. Both of the loader’s positions were on the right side, for loading the main gun and the coaxial machine gun. The driver sat in the front of the hull, in the center, while the radio operator sat to his left. He was also responsible for operating the hull machine gun or flamethrower.
Propulsion
The engine was to be the 850 hp V-2SN diesel engine, developed by Plant No.75 with an AM-38 aviation supercharger and pressurization system. Fuel reserve was for 825-845 liters. However, due to the unreliability of the engine during the KV-220 trials, a 700 hp V-5 engine was used instead. The planned top speed was to be 30 km/h.
Top view of the hull of the KV-3 showing various elements from within, such as the engine, final drive, gearbox, fuel tanks or escape hatch behind the driver’s chair.
Source: Yuri Pasholok, edited The KV-3 transmission designed by N.F. Shashmurin. The document was signed by him on 25 April and then by J.Y. Kotin.
Sources: ASKM via Stalin’s Supertanks IS-7
Armament
The main armament was the 107 mm ZiS-6 developed at Plant No.92 by V.G. Grabin. Praised for its good anti-tank capabilities, the gun was meant to equip the entire new line of super-heavy tanks. In total, 45 shells were stowed in the tank, within the turret and inside boxes placed longitudinally and transversely in the center of the hull, underneath the turret ring. During the trials of the gun on the KV-2, the gun could penetrate 120 mm thick armor plates angled at 30° from 1,600 meters.
Secondary armament consisted of a 7.62 mm DT machine gun mounted coaxially, to the right of the main gun. On the left side of the frontal hull armor plate, either a ball-mounted DT machine gun or a flamethrower were to be mounted. There were 60 drums for the machine gun (47×60 rounds) and an additional 15 shots for the flamethrower. The crew was equipped with an unspecified amount of PPSh 7.62 submachine guns.
Armor
As the tank was intended to sustain fire from the German 88 mm anti-aircraft guns, the thickest armor was in the front hull plate and front turret, at 120 mm, with other frontal armor portions being 115 mm thick. The rest of the turret was 115 mm, while the rest of the hull was 90 to 100 mm.
Conclusion
The KV-3 proved to be an ambitious plan to quickly create a well-armored and well-armed tank based on previous designs. While work began smoothly, several delays from the Izhora plant and the start of the war greatly delayed the project to the point of cancellation. The complexity of the stamped turret construction, which required new tooling, as well as the unrefined engine sent the project into a spiraling series of delays. However, on paper, the tank would have been an impressive feat, though likely even more plagued by reliability issues than the KV-1.
KV-3 (Object 223). Illustration by Pavel ‘Carpaticus’ Alexe
KV-3 (Object 223) Specifications
Dimensions (L-W-H)
7.85 x 3.42 x 2.95 m
Total weight, battle-ready
67-68 tonnes
Crew
6 (Commander, gunner, driver, radio operator/bow gunner, 2x loaders)
Propulsion
V-5SN 12-cylinder diesel, outputting 850 hp w/ AM-38 supercharger
Soviet Union (1932-1933)
Truck – 1 Prototype Built
The 1930s saw the Soviet military start to take a mature approach regarding mechanization, but it was industrially far behind, especially considering their large army. Mass production of simple trucks such as the ZiS-5 and GAZ-AA was not enough, and a heavier truck was needed. One of these was the YaG-12, essentially a YaG-10 truck with 8×8 wheel drive. A single prototype was built, tested, and shown at the October Revolution parade in 1932. Although a capable machine, the factory’s low production capabilities, the truck’s high price and the maintenance cost, as well as the military’s desperate need of simpler trucks, cut the project short.
YaG-12 driving over frozen mud and a trench during trials at the NATI proving grounds.
Source: Russia DARPA
Development
In the late 1920s, as the Soviet Army was beginning its tedious process of troop mechanization, a crucial element needing desperate attention was trucks. Up until this point, the main Soviet truck in military use was the AMO-F-15, a license-produced Fiat F-15, which itself was launched in 1911. Consequently, most of the logistical and transport duties of the massive Soviet Army were done by horses. The solution was to begin mass production of trucks across several factories, with the help of Western patents and factory toolings. As a result, two of the most famous Soviet trucks of the Second World War were born, the GAZ-AA and ZiS-5. However, both of these trucks were light, around 2 and 3 tonnes respectively, and a larger truck was needed. Thus, Plant No.3 Yaroslavl State Automobile Plant (YaGAZ) was tasked with production of the Ya-5, a 4.8 tonne truck, an improved variant of the Ya-4 using an American engine. The YaGAZ plant had previous experience with heavy trucks, starting with the Ya-3, but only 160 units had been built.
The Ya-5 heavy truck had a weight of 4.8 tonnes and load capacity of 5 tonnes. It was produced from 1929 to 1934.
Source: Cars of the Red Army 1918-1945
By 1931, YaGAZ was tasked with producing a new 3-axle heavy truck to better cope with the needs of the military. This would become the YaG-10, which kept much of the same features as the previous trucks, but had an extra axle and longer flatbed, thus the weight increased to 6.8 tonnes and load capacity to 8 tonnes. The rear bogie housing the two rear axles was a copy of the British WD type, while the engine was an American Hercules YXC outputting 96 hp.
By 1932, the YaG-10 was to enter production with 100 units built per year. However, a multitude of issues prevented this, and by 1940, when production ceased, only 333 units had been built.
YaG-10 truck leaving the factory.
Source: Engines of the Red Army
Shortly after the YaG-10 entered production, YaGAZ was tasked by the Scientific and Technical Committee of the GABTU (Main Directorate of Armored Forces) with developing an even larger and heavier truck, not just for increasing the maximum payload capacity, but more importantly, to increase the cross-country capabilities of the truck. This was a very important element in the Soviet Union at the time, as it was a country which lacked an infrastructure network for which not even 3-axle trucks were often adequate. Furthermore, towing heavy artillery systems proved to be a great challenge as well, and the need for a larger truck with good off-road capabilities became clear.
The larger truck was to be an 8×8 vehicle, largely inspired by what Soviet dellegations saw in international exhibitions, especially regarding the British AEC Mammoth and Guy 8×8 artillery tractor. After failed attempts to purchase or license-produce these trucks, the Soviets figured that they would have to create their own design; and quickly. During the same period, the Armstrong-Siddeley Pavesi P4 articulated 8×8 vehicle and AEC Roadtrain were already in development, and the Soviet Union needed their own counterpart for geopolitical reasons.
Development of the new truck began at YaGAZ with the chief designer being A.S. Litvinov, head of the plant’s design bureau. Heavily involved in the project was also the director of the plant, V.A. Yelenin, and engineer V.V. Osepchugov. Their task was extraordinary, as the plant lacked the skill and experience in such complex systems, their entire truck lineup having been essentially just made by tinkering with the engines of the same chassis. The new truck was to be named YaG-12, not to be confused with the Ya-12 tracked artillery tractor, produced between 1943 and 1946, also in Yaroslavl.
The drawings were ready by summer 1932 and manufacturing began in September. By November, the YaG-12 was ready. This hasty schedule was partly due to Yelenin’s promise to the military of delivering the truck for the 15th October Revolution anniversary, which actually took place on 7 November according to the Gregorian calendar. The entire plant was working towards this goal. In the last 3 days, there were 3 shifts a day, while the engineers and directors were working constantly. On 5 November, at 23:00, the engine was started for the first time, and the last checks were made. At 23:30, the truck left the shop. At its wheel was the head of the YaGAZ production department, M.K. Mroz, and next to him was Litvinov. After a speech and meeting, the YaG-12 was accompanied by several YaG-10, all headed for Moscow.
YaG-12 8×8 truck at the Yaroslavl plant.
Source: Topwar
Design
The basis for the YaG-12 was the 3-axle YaG-10 truck. Many components were recycled, from the cabin and engine cover to wheels. The truck maintained a standard layout, with the engine in the front, central cabin, and flatbed in the rear. Compared to the YaG-10, the flatbed was shorter, due to the additional space needed for the wheels and drive mechanisms.
The main external change was the addition of a second bogie in the front of the truck, with two wheels per side. To accommodate this, the fender was enlarged, running across the entirety of the hood and most of the cabin. While most of the truck was made out of thin sheet metal, the flatbed was wooden and the cabin had wooden elements. The rear bogie remained virtually unchanged from the YaG-10, with four wheels with two sets of tires each. The tires were standard 40×8 inch ones, which were not great for off-road use, but the truck having 12 of them increased its performance. There was a tire inflation compressor, but no deflation system. The front wheels had just one tire to facilitate easier steering, considering that the steering was mechanical. A spare tire was located underneath the flatbed, above the transfer case. A trailer hitch was mounted at the end of the chassis frame, and a hook at the front. A winch was also mounted in the center of the frame, allowing for the cable to be used both in the front and rear of the vehicle.
The YaG-12 crossing a trench at the NATI proving grounds.
Source: Zr.ru
Engine and Propulsion
The YaG-10 had a Hercules YXC 96 hp engine, but it was deemed underpowered for the new truck. Instead, due to the Soviet inexperience in engine design and manufacture, a Continental-22R engine was used, with a straight-six configuration, outputting 120 hp and with an internal volume of 8600 cm3. Cylinder diameter was 114.3 mm with a stroke of 139.4 mm and a compression ratio of 4.6. This engine allowed the 8 tonne truck to reach a top speed of 45 km/h and a minimum fuel economy of 52 l/100 km. An 164 liter fuel tank was placed underneath the cabin crew’s bench. The vacuum booster was borrowed from the YaG-10 as well.
The most complex part of the truck was the power transfer system, a complete novelty for the Soviet auto industry. The dry-clutch and four-speed and one reverse (other sources claim 8 forward+2 reverse) manual Brown-Lipe-554 gearbox was reused from the YaG-10. A specially designed transfer case powered all four axles through individual drive shafts.
Due to the lack of machining abilities of the factory to produce helical gears, the YaG-12 used spur gears in its mechanical components instead. While these gears are easier and cheaper to manufacture, they are far less durable and are much louder, which allegedly made the YaG-12 have an unique “howling” sound when driving. For similar reasons, no tapered roller bearings were used, or any differentials on the central driveshafts.
Before the system was assembled on the truck, a special unit was made for testing purposes. While the system worked reliably, it was noted to be rather heavy. In total, 9 drive shafts, 18 universal joints, 30 ball and 12 roller bearings were used on the power transmission system.
Side cutout view showing the different mechanical elements of the truck. Note the mountain brake behind the rear wheel.
Source: Bronetechnika
Suspension and Bogies
While the rear bogie remained mostly identical to that of the YaG-10, the front was completely redesigned. A second bogie was added, with both front axles being able to traverse for better steering. The steering was done via a worm gear and two longitudinal steering rods, one per axle. Each bogie was hinged to the frame in the center and sprung with 2 leaf springs, allowing for dependent movement of each axle. As one axle went up, the other went down. Furthermore, the axles were sprung to each other with a second leaf spring to smoothen out the potential jerkiness of the bogie mount. Drum brakes were mounted only to the wheels on the rear bogies, with 100 mm pads and 460 mm inner drum diameter. The hand brake was a band type and was in the transfer case, acting on all four drive shafts. A so-called mountain brake was added as well to prevent brake failure at steep angles. It was hinged to the rear hitch, from where it could be stuck into the ground.
This suspension layout would offer excellent cross-country performance across various types of terrain, allowing for all wheels of a bogie to have contact with the ground, increasing load dispersion and improving traction.
Diagram showing the YaG-12 crossing a hill. Note how all wheels are touching the terrain regardless of angle.
Source: edit from Autoretrolab The YaG-12 at the Yaroslavl factory during suspension testing.
Trials and Fate
By 19:30 on 6 November 1932, the YaG-12 truck completed its approximately 250 km trip to Moscow and participated in the parade the next day. It made quite the sensation, and was the subject of propagandistic newspaper articles, showing how the USSR managed not just to catch up, but also surpass British designs in such a short period of time. After the parade, the truck was sent to the NATI proving grounds, where it was tested over various terrains and obstacles. The YaG-12 could climb 30º slopes, cross 1.5 m wide trenches, and climb over a 40 cm obstacle. It crossed 60 cm deep water and drove through 50 cm deep snow. Ground clearance was 32 cm. Load tests were made to ensure that the truck could support 12 tonnes on roads and 8 tonnes on soft terrain. A special metal and rubber track, first used on the YaG-10, was mounted over the wheels of the last bogie, further improving traction.
Naturally, several small improvements had to be made, but the experiment proved to be a success, and the GABTU originally requested 7 more trucks to be built during 1933. However, after the YaG-12 was moved over to a military unit in Saratov for further testing, all traces were lost.
The truck indeed had incredible potential, at least on paper, for both the Soviet military, but also for various civilian applications. Its excellent carrying capacity combined with superior off-road capabilities would have made it an excellent vehicle for carrying heavy artillery weapons and munitions, as a gun platform and much more. Even for civilian applications, such as dump trucks, it would have found success. However, the realities of the Soviet industry put an end to this otherwise capable vehicle. The Soviet Union as a whole desperately needed trucks, of any kind, and slowing down the YaGAZ production line even more was not an option. The truck was also expensive and mechanically complex, two features which the Soviet Army and military industrial complex could not support at the time. Alas, even with the production of trucks such as the ZiS-5 and GAZ-AA, the Soviet Union struggled to keep up with truck demand, the situation peaking during the war, when the Soviets had to rely more on Lend-Lease trucks from the USA. As for the YaG-12 designers, both chief designer A.S. Litvinov and factory director V.A. Yelenin were killed during the Great Purge, in 1939 and 1938, respectively.
The YaG-12 driving through thick mud with chains for extra traction across all wheels.
Source: Kolesa
Just a year later, in 1934, the Department of Armored Vehicles of the Military Academy of Mechanization and Motorization built a prototype of an 8×8 vehicle, though the janky homemade vehicle was more of an educational experiment, rather than anything meant for mass-production. Work on 8×8 trucks would only resume in the 1950s, with the EATE-1 8×8 truck, followed by several others. The first 8×8 trucks to enter military service with the Soviet Union were the ZiL-135 and MAZ-535, nearly two decades after the YaG-12.
The EATE-1 8×8 during trials, 1952.
Source: Cartruckbus.ru The ZiL-135L, here as a dump truck for civilian use. Production of these trucks began in 1959.
Source: Topwar The MAZ-535 began mass-production in 1958 and remains one of the most successful and powerful trucks to be built by Soviet factories.
Source: mzkt.by
As for the YaGAZ plant, work on improving and producing heavy trucks continued, at a slow pace. During the Second World War, the plant produced and assembled components for other factories, as well as assembling the Ya-12 tracked artillery tractor. Towards the end of the war, the plant resumed development and production of its own truck designs for both military and civilian purposes, preparing for peacetime production, one such truck being the YaAZ-200.
Conclusion
Despite YaGAZ’s best efforts to provide a capable machine and regardless of the truck’s performance, the project was a dead end. The factory had a very small production output of much simpler Ya-4 and YaG-10 trucks, which were desperately needed by both military and civilian users. The truck’s high price also meant that the military could not afford as many as it needed, especially in terms of maintenance. But the YaG-12 also sought to push the limits of Soviet truck design, and successfully managed to do so. For an industry limited to engine swaps and license production, this 8×8 vehicle created in such a short period of time was truly an impressive feat, and amongst the first 8×8 trucks in the world.
The 8×8 truck was capable of driving over steep inclines and thick snow.
Source: Topwar YaG-12. Illustration by Pavel Alexe.
YaG-12 Specifications
Dimensions (L-W-H)
6.584 x 2.39 x 2.77 m
Total weight
8 tonnes, 20 tonnes fully-loaded
Crew
6 (commander, main gunner, main loader, secondary gunner, secondary loader & driver)
KV-4 (Object 224) Turchaninov. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 was conceived in spring 1941 to deal with the rumors of new, powerful German heavy tanks. Its development process consisted of a design competition between several SKB-2 workers. One of these designs was made by the young engineer G.A. Turchaninov, heavily resembling an enlarged KV-3, which was being developed simultaneously. However, his design was not taken into consideration, and has been largely forgotten since.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The KV-4 (Object 244) Soviet heavy tank program was initiated by the Soviet Union in response to the German expansion over Europe, despite the Molotov-Ribbentrop Pact. The program aimed to develop a new heavy tank to match the alleged German heavy tanks which were rumored to be in development. The KV-1 heavy tank, which was rushed into service due to Stalin’s requests, had significant quality, weight, and reliability problems. The most advanced heavy tanks in development at the time were the KV-150 and the KV-220, which had even more serious reliability issues and were still in the prototype testing phase. Thus, the GABTU set out to develop a new heavier tank to match the suspected German tanks.
The requirements for the new heavy tank were laid out on 21 March 1941, which included a 107 mm ZiS-6 gun, armor of 120 mm to 130 mm all-round, a weight between 70 to 72 tonnes, a M-40 diesel aviation engine with 4 TK-88 turbochargers for propulsion, a secondary 45 mm gun, at least three 7.62 mm machine guns, and a flamethrower. The development of the KV-4 took place at the LKZ (Kirov Leningrad Factory) SKB-2 design bureau, the same office responsible for all the previous KV tanks. The first prototype production was assigned to the Izhora plant based on LKZ drawings. Blueprint deadline was set for 17 July 1941.
The GABTU edited their request on 7 April, demanding a heavy upgrade of the KV-220, named KV-3 (Object 223), that would act as a stopgap until the heavier tanks were ready, and an even heavier tank named KV-5 (Object 225). To better fit the KV-4 between the two new vehicles, its weight threshold was lifted to at least 75 tonnes, and 125 mm of armor at the sides. The deadline was tightened to 15 June. Work on all 3 tanks commenced at SKB-2 design bureau, which was headed by J.Y. Kotin.
Kotin challenged his engineers to a design competition, and 24 designers entered the competition with equally as many different designs presented. The winners were announced on 9 May, with 13 designers having received monetary prizes. However, work on the KV-4 stagnated severely after the competition was ready. Most of the efforts shifted to the KV-5, which was developed based on knowledge from the KV-4. However, the KV-5 was in a very early stage when the German Reich began their invasion of the Soviet Union, and their quick advance into Soviet territory put great strain on the LKZ tank factory, which had to switch focus on optimization and repair of KV-1 and KV-2 tanks.
By September 1941, the German forces were advancing towards Leningrad, and the SKB-2 design bureau was ordered to evacuate to the ChTZ in Chelyabinsk. The KV-4 project was canceled due to the evacuation, and no prototypes were produced.
One of the designs submitted was by the young Military-Engineer G.A. Turchaninov, though he was not rewarded for his tank design.
G.A. Turchaninov
During his studies at the Military Academy of Motorization and Mechanization, Turchaninov worked on his undergraduate practice at the SKB-2 design bureau. He worked on the general design of the SMK tank, as well as a mine-clearing roller. Later, he was part of the design team of the KV tank, both in terms of general layout, but also the transmission. By 1940, he had finished his studies and began working at SKB-2 as a Military Engineer. With the outbreak of the war, he began work on crew training on KV-1 tanks and the fortifications of Leningrad.
Group photo of engineers at the first KV trials, 1940. G.V. Turchaninov can be seen in the last row, pointed with the arrow. Photograph source: Constructors of combat vehicles
Design
Unlike many of the other KV-4 tanks designs, Turchaninov’s design was very sensible in layout, without any extravagant features. It was very similar to the final KV-3 layout, with a rounded turret and standard hull layout, a stepped front portion, much like on the earlier KV tanks, central turret and fighting compartment, and powerplant and final drive in the rear.
The most bizarre feature, and likely a flaw in the design, was the mounting of the 45 mm 20-K secondary gun in the center of the front hull plate. While this option offered the maximum firing angle, its range was still inferior to that of competing KV-4 designs, which usually placed the secondary gun in a separate turret or coaxial to the main gun. However, the main problem with this layout was that there was no room in the hull for a designated gunner. Thus, the driver was forced to be its gunner.
The engine, as requested by the GABTU, was the experimental 1,200 hp M-40 aviation engine, capable of running on kerosene and diesel. It was boosted with four TK-88 turbochargers. The fuel tank was over the 5th roadwheel, underneath the ammunition stowage racks.
Side cutout view of Turchaninov’s KV-4 proposal. Source: Stalin Supertanks IS-7Top view of the tank, showing the rounded turret edges and traverse of the hull-mounted secondary gun. Source: Stalin Supertanks IS-7
Crew
The tank’s crew was of 6, consisting of commander, main gunner, 2x main loaders, driver/secondary gunner, and secondary loader/flamethrower operator.
The gunner and commander were seated in the main turret, on the left side of the main gun, with the commander behind the gunner. The two loaders were on the other side of the gun, with one loading the shells in the gun and the other lifting them up from the hull stowage racks.
The driver was seated to the left side of the hull, but due to the central mounting of the secondary gun in the hull, the driver was also forced to aim and fire the gun. The loader was seated on the right side of the hull, loading the secondary gun but also firing the flamethrower, placed on the extreme right side of the hull.
Armament
The main armament used on all KV-4 proposals was the 107 mm ZiS-6 gun. It was developed by V.G. Grabin at Plant No.92, starting in December 1940 and finishing first prototype in May 1941.
The gun was an excellent anti-tank weapon, with a muzzle velocity of 800 m/s, and during trials, was able to penetrate 120 mm of armor angled at 30° from 1,600 m.
Secondary armament consisted of the older 45 mm 20-K, which was still the most widely used gun on armored vehicles at the time. Although it was completely dated for anti-tank use, it was still a cheap and readily available gun for soft-skin targets and infantry. The main problem in Turchaninov’s design was its position. While most designers placed it in an independent turret or coaxially to the main gun, Turchaninov placed it in the front hull plate, limiting its traverse to 30° in both directions.
For close-range infantry defense, the tank was equipped with three to four 7.62 mm DT machine guns. An unspecified type of flamethrower was mounted on the extreme right side of the front plate, with 30 shots.
Armor
Like most KV tanks, Turchaninov’s KV-4 had the same armor thickness all around, 125 mm. Only the turret’s roof and engine/hull’s deck plates were just 40 mm thick, while the hull’s belly was 50 mm thick.
The shape of the turret, clearly inspired by the KV-3’s (Object 223), is noteworthy. It is important to note, however, that this rounded shape would have been achieved via stamping the RHA plates, rather than casting. Soviet industrial technology severely lacked the ability to reliably cast such thick armor plates before the war, and this would be a continuous issue throughout the war.
Fate of the Project
By the end of May, the competition was over, the winning designs were announced, and their respective designers awarded accordingly. Unfortunately, Turchaninov was not amongst these. There are no documents regarding why certain designs won and others did not. We may only speculate based on the design looks and the engineers’ relation with factory director I.M. Zaltsman and head of SKB-2 J.Y. Kotin, the ‘judges’. Winner of the competition was N.L. Dukhov, who proposed an enlarged KV-220 design. After the competition ended, work on the KV-4 completely stalled, with focus shifting to the KV-3 and KV-5. Work progressed through summer 1941 and as with the start of the war, but was halted in September, when the SKB-2 design bureau was transferred from Leningrad to Chelyabinsk due to German forces advancing towards the city. Work on the heavy KVs never restarted.
Photo collage showing the front and side of the KV-3 mock-up. Source: Yuri PasholokPhoto collage showing the side of the KV-3 mock-up. Note the complex turret shape, including the bulge for the commander’s cupola. Source: Yuri Pasholok
Conclusion
The design path chosen by Turchaninov seemed like a fail-proof formula, heavily inspired by the KV-3, using the complex turret shape and standard hull layout. Despite this, the poor placement of the secondary armaments and lack of innovation likely put this design at a disadvantage and was not considered. As a whole, in spite of the efforts of Turchaninov and the other designers, the KV-4 program proved to be a failure, born from the impulsive acts of a disorganised military leadership, and killed by the realities of war.
KV-4 (Object 224) Turchaninov. Illustration by Pavel Alexe.
KV-4 Turchaninov Specifications
Dimensions (L-W-H) (approx.)
9.8 x 4 x 3.82 m
Total weight, battle-ready
89.5 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver,, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
38 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3-4x DT 7.62 mm machine guns
Flamethrower (30 shots)
KV-2 with 107 mm ZiS-6, ilustration by Pavel Alexe.
Soviet Union (1941)
Gun Testbed – 1 Converted
In summer 1940, one of the ways through which Soviet officials wanted to improve the firepower of their heavy tanks was to mount an 107 mm gun in the KV-2. This idea was later dropped in favor of new, heavier tanks which were to directly mount the new 107 mm ZiS-6 gun. However, due to the slow progress of development, the KV-2 was brought back, and was used as a gun testbed for firing trials. Due to the start of the war, neither the ZiS-6 nor the heavy KV tanks designed to use it entered service.
Development
Even before the KV-1 and KV-2 entered serial production, Soviet officials sought to improve their raw characteristics. One direction was to add even more armor, like on the T-150. Another was the improvement of the main armament. A document from June 1940 discussed the future of Soviet heavy tank developments. The second point mentioned the mounting of a high-power 107 mm gun in the KV-2. The gun was to have a muzzle velocity of 730-750 m/s and penetrate 100-110 mm of armor at 1,000 m. High rate of fire, high ammunition capacity, as well as both AP and HE shells were desired.
At the time, the KV-1 was still being produced with the underwhelming stopgap 76 mm L-11 gun, while the KV-2 was fitted with the 152 mm M-10T, which left much to desire in most areas. A 107 mm gun with such high velocity would have been formidable against any armored target at the time. It is perhaps this state of “overkill” which delayed the materialization of this project. Furthermore, the situation of the Soviet tank industry was not optimal. The creators of the KV tanks, the SKB-2 design bureau at LKZ (Leningrad Kirov Plant) were stressed with bug fixes for the KV-1 and were already tasked with the development of the T-150 and T-220 heavy tanks. Likewise, the creators of tank armaments, Plant No.92, were just beginning work on the much needed new tank guns, the 76 mm F-27 and 85 mm F-30.
New High-Power Gun
Plant No.172 had the 107 mm M-60 divisional anti-tank gun under development since late 1938, entering service in October 1940 under the designation M1940. However it was deemed too heavy to be mounted in a tank, thus a new gun was needed. It was likely this gun that was originally (in June 1940) meant to be mounted on KV-2. Based on V.G. Grabin’s memoirs (head of Plant No.92 design bureau), a KV-2 had been fitted with an 385 tonne/meter, 107 mm gun, likely an ancient M1910/1930 gun, to test the viability of mounting such a large gun.
The M1940 divisional gun. Although often assimilated with the ZiS-6, the latter was a completely new piece, specifically made for use on armored vehicles.
Source: Alf van Beem
A first mention of the 107 mm F-42 appeared on 16 December 1940, when Plant No.92 was already in the process of producing the first prototype. Curiously, they had requested a KV-1 tank to test fit the gun, and due to delays, allegedly fitted the 107 mm gun prototype into the T-28 medium tank instead. No testing was carried out due to lack of ammunition.
Here, it is worth mentioning the differences between the F-42 and M-60 anti-tank guns. The F-42 had a higher muzzle velocity of 800 m/s compared to the 730 m/s on the M-60. The barrel was also longer on the new gun, 5185 mm compared to 4605 mm on the M-60. The breech had also been altered. The M-60 used a clumsy door breech lock, while the F-42 used a vertical sliding breech lock. The shells of the F-42 weighed 18.8 kg.
Later documents reveal that this new 107 mm gun was originally to be designed at LKZ, with a deadline of November 1940, but the plant refused to do so. Only in January 1941 did the SKB-4, the artillery design bureau of LKZ, start work on their own 107 mm gun, the 412-2V, but it was canceled shortly thereafter due to the progres of the F-42.
Aside from the KV-2, in June 1940, the KV-220 was also proposed to be armed with an 107 mm gun. This idea came from the initiative of Grabin and J.Y. Kotin, head of the SKB-2 design bureau, despite the fact that the GABTU specifically requested the main armament of the KV-220 to be the F-30. By August, SKB-2 engineer G.N. Moskvin began working on this hypothetical weapon swap. He concluded that an 107 mm gun would have been too large to fit in the turret of the KV-220, especially considering how long the shells were, at 120 cm, making loading nearly impossible.
By December, it was clear that this gun was supposed to be the F-42, and Grabin still believed that his 107 mm gun would fit in the KV-220. To prove this, he traveled to Leningrad to convince Kotin. He then climbed into the turret (allegedly struggling to fit through the hatch) and attempted, and failed, to lift the 18.8 kg shell from the hull floor into the turret.
The story of the F-42 fitted in the KV-220 did not end here. On 19 February 1941, Marshall Kulik, who was overseeing progress at LKZ, submitted a report where he mentioned that the KV-220s second prototype was to be armed with the F-42 at Plant No.92, where the tank’s turret was waiting. Even more bizarre was that Kulik also mentioned that an F-42 gun was to be mounted on the KV-1 by May, but LKZ, understandably, outright refused to do so.
An abandoned KV-2 with the newer turret.
Source: Global Strategy
Tanks vs Guns
On 11 March 1941, the F-42, by this point renamed ZiS-6, re-entered the picture. Soviet intelligence services sent a report to the GABTU and Soviet leadership regarding the development of German tanks. In the section on heavy tanks, several projects were described, but perhaps the most alarming was that of a 90-tonne tank armed with a 105 mm gun.
This was not taken lightly, as neither the KV-1 nor the KV-220 in development were able to deal with such threats. Thus, SKB-2 was tasked by the GABTU with the design and development of a new heavy tank, specifically armed with the ZiS-6 gun, and weighing 72 tonnes. It was named KV-4 (Object 224).
A segment from Grabin’s memoirs showcases perfectly the situation of development at the time. On 4 April, Grabin was having a phone call with Stalin:
Stalin – “Hello, Comrade Grabin,- I want to consult with you. It is believed that a heavy tank which is armed with a low-power gun cannot meet the tasks of a heavy tank. Currently, the issue of re-equipping it is being considered: instead of the 76-mm gun, it is proposed to put a powerful 107 mm. I would like to know your point of view on this issue. It may be difficult for you to evaluate this proposal, since the heavy tank is armed with your 76-mm cannon.”
Grabin – “When our design bureau was issued tactical and technical requirements for a 76-mm gun for a heavy tank, we carefully studied the issues related to tanks and their weapons, and came to the conclusion that the 76-mm gun for a heavy tank is unpromising and does not even meet the requirements of today. We believed that a heavy tank should be armed with a more powerful gun, the projectile of which would penetrate the armor of its tank from a distance of 1000 m. The 76-mm cannon ordered to us was created and installed in the KV-1 tank.”
Stalin – “So, you’ve long had an opinion about the insufficient power of the 76 mm gun on heavy tanks?”
Grabin – “Yes, Comrade Stalin.”
Stalin – “It’s a pity that I didn’t know about it before. So, right now, our estimates do not contradict. Tell me, please, is it possible to put a powerful 107 mm gun in a heavy tank?”
Grabin – “Yes, Comrade Stalin.”
Stalin – “Are you sure that a powerful 107-mm gun can be put in a heavy tank?”
Grabin – “I am quite sure that a 107-mm powerful gun can be put in a heavy tank. But we consider the KV-2 tank unacceptable in terms of the design of the turret. The dimensions of the turret are large, and the shape of the turret is not optimal. Such dimensions for the 107-mm gun were not required.”
Stalin – “So you claim that a powerful 107-mm gun can be installed in a heavy tank?”
Grabin – “Yes, I am deeply convinced that a powerful 107-mm gun can be put in a heavy tank. If I understand you correctly, this gun should be higher in power than the 107 mm modernized?
Stalin – “You understood me correctly. The fact that you already have experience in installing a 107 mm cannon in a heavy tank is great. So, we will install a powerful 107-mm gun in a heavy tank?”
Grabin – “Yes, Comrade Stalin.”
Stalin – “This is very important, Comrade Grabin. As long as we do not arm a heavy tank with such a gun, we cannot be calm. The task must be solved as quickly as possible. This is required by the international situation. Tell me, could you be in Moscow tomorrow? We really need you here.
The following day, Grabin found himself at the meeting with the Secretary of the Central Committee of the All-Union Communist Party A.A. Zhdanov. Also present were the head of the GABTU ,Lt. Gen. Y.N. Fedorenko, as well as LKZ representatives J.Y. Kotin and I.M. Zaltsman, as well as V.G. Grabin and others.
Some of the individuals present at the Commissars office on the issue of mounting 107 mm guns on heavy tanks. From left to right: A.A. Zhdanov, V.G. Grabin, J.Y. Kotin, I.M. Zaltsman, Y.N. Fedorenko.
Zhdanov opened the meeting with a bold message:
“The party and the government attach great importance to the rearmament of a heavy tank, I ask you to approach with all seriousness the development of tactical and technical requirements and to determine the timing of the creation of a tank and gun. Deadlines should be minimal. Fascist Germany is walking around in the West. It is possible that in the near future it will attack us. We learned that the Germans are working on the creation of thick-armored tanks with powerful weapons. Our heavy tanks are poorly armed. […] “The draft decision needs to be prepared as soon as possible, therefore, you will have to work late, without leaving the Central Committee. You will eat here, we will provide it. A room is set aside for your work. I am at your disposal at any time…”
Things started off poorly. The LKZ engineers refused to mount a 107 mm gun on their tank. Most likely, this tank was the KV-220 and/or Object 222. This situation brought up a long-time argument between Kotin and Grabin, whether it was the mounting of the 107 mm gun in the KV-220, KV-1, or the mockup T-28 Grabin received instead of an actual tank for the testing of his F-39 gun. The situation was aggravated when Grabin, rather famously, said that the tank is just a chassis for the gun. Naturally, the tank designers did not take this lightly. After Zhdanov calmed down the 5 culprits, work commenced, but not smoothly. Grabin suggested that the new gun had to have 550 tonnes/meter, and with a longer barrel than the M-60. The tank designers objected, fearring that a too long gun would scrape up mud and lead to barrel damage.
The second day, most of the intricacies had been solved, with the exception of when everything should be ready. Once again, Zhdanov intervened:
Zhdanov – “When will the tank be ready?”
Kotin – “As soon as Grabin gives the gun, the tank will be ready,”
Zhdanov – “Comrade Grabin, when will you be able to give the gun?”
Grabin – “In forty-five days,”
Here Grabin recalled that everyone burst into tears, and that he was the only serious one in the room.
Zhdanov – “Comrade Grabin, we have gathered here to seriously resolve the issue, and you are joking.”
Grabin – “No, I’m not kidding, the term I mentioned is justified and quite serious.”
Zhdanov – “You continue to joke, go and think again.”
Grabin also highlights that this topic of 45 days was the subject of many jokes that he would hear often. With further consultation, the tank designers suggested that the number of days should be doubled, if not tripled. When it became clear that progress was not made, Zhdanov stepped in, again.
Zhdanov – “Well, Comrade Grabin, did you think through the deadline?”
Grabin – “Yes.”
Zhdanov – “Probably not forty-five days?”
Grabin – “Forty-five days, Comrade Zhdanov.”
Zhdanov – “And yet you are not serious. I think that the term should be significantly increased.”
Grabin – “Comrade Zhdanov, why does a short term cause homeric laughter and is considered frivolous, while a long term finds support and approval?”
Zhdanov – “We do not know of a single case where a new tank gun was created not only in forty-five, but even in ninety days. We believe that this will be a great opportunity for us to work together with our partners.”
Grabin – “I agree. Previously, it was not the case. Now it is. I ask you, Comrade Zhdanov, to write down in the draft decision: “The deadline for the production of a prototype tank and gun should be set forty-five days from the date of signing the decision.”
This was the deadline set in the contract. Grabin was set to leave back to Gorky even before the contract was fully signed. Before leaving, Zhdanov said that if Grabin was not able to meet the deadline, to just call him and tell Stalin and they would extend the contract. Grabin thanked him.
Naturally, much of the above should be taken with several grains of salt, as these clearly-one sided memoires were written many years after the fact. Nonetheless, they still provide valuable information on how Grabin viewed the ordeal.
On 7 April, the contract was signed, and further heavy tanks were ordered. The KV-3 (Object 223) and KV-5 (Object 225) were also meant to fit the same 107 mm gun. The KV-3 used an up-armored hull of the KV-220 and an enlarged turret, specifically made to fit the ZiS-6. The KV-5 was even larger than the KV-4, weighing 90 tonnes and with 170 mm of frontal armor.
Prototype of the ZiS-6. Note the coaxial DT machine gun.
Source: Yuri Pasholok Collage of 2 photographs of the KV-3 mockup.
Source: Yuri Pasholok
The Gun is Ready, the Tanks are Not
Now that there were several vehicles in the works to mount the ZiS-6, work on it progressed. On the same day as signing the contract, 7 April, over at Plant No.92, a development program for the ZiS-6 was drawn up. Firing trials were to be undertaken on 15 May. Between April and May, ammunition production was set, and ballistic trials were laid out. However, several changes had to be made to the gun for use on tanks. Firstly, the shells were to be single piece, as opposed to 2-part. A gun rammer and bore evacuator were to be added to the gun for use on these tanks. On 14 May, the ZiS-6 was finished. Grabin was now able to boast that he made his gun one week faster, in just 38 days.
Naturally, work on the ZiS-6 was far more advanced compared to the heavy KV tanks and the gun had to be tested. The only vehicle readily available and able to mount the ZiS-6 was the KV-2. Thus, on 17 April, Fedorenko sent a letter to Zhdanov ordering that said gun was to be mounted on the KV-2 for trials. On 27 May, Plant No.92 shipped a ZiS-6 gun with serial number 2 (other sources claim 1) to LKZ for mounting on the KV-2, and arrived on 1 June. It was issued that the Izhora plant was to manufacture the gun mantlet and gun mount of the KV-3 and be mounted on a KV-2. Yet the Izhora plant was moving slowly, causing Marshall Kulik to intervene on 18 June, ordering the Izhora plant to deliver required parts and that testing shall commence with the ZiS-6 in a KV-2 with serial number B-9680.
While the KV-4 and KV-5 were long-term projects, the KV-3 was to act as a stopgap. On a contract signed 1 June, KV-3 was to enter production in August 1941, with 500 units to be built until the end of the year. Thus, Plant No.92 also had to deliver 500 guns before the end of the year. Grabin claimed that he began production of the guns far before it was ordered by the military. By the time the order of production was given, they had “dozens” of guns ready.
Front view of the KV-2 testbed with the new gun. Note the KV-3 mantlet.
Source: CAMO 38-11355-175
Design & KV-2
The KV-2 was born from the urgent need for a bunker buster to fight through the Finnish fortifications on the Karelian isthmus during the Soviet-Finnish war. However, due to the immediate need, a specially designed vehicle could not be finished in time. Thus, as a quick measure, an enlarged turret armed with an 152 mm M-10T gun was mounted on a prototype hull of the KV tank. The assault tank would prove slow and overweight, while the gun, despite its large size, had underwhelming performance against static defenses. The first 24 vehicles used a tall, complex turret, while later production models featured a more compact and efficient turret. In total, 204 such vehicles were built, but most were lost in the first stages of the fight against the Axis, most breaking down or being captured.
The first KV-2, called just KV big turret, or U-3.
Source: Juri-rust
The crew was the same as usual, comprising six men; commander, gunner, loader, and the loader assistant in the turret, and the driver and radio operator in the hull. As the hull was identical to that of the KV-1, it was powered by an 500 hp V-2K diesel engine, for a top speed between 30-35 km/h. It had two fuel tanks for a total of 600 liters.
As the tank was used as a testbed, much of the KV-2 tank remained untouched, with the main difference being that the gun mantlet had been changed to that of the KV-3 to accommodate the new gun. Due to the accelerated nature of the work, several details had not been worked out or converted. Firstly, the ammunition stowage racks had not been changed, so rate of fire was particularly low.
Interior view of the ZiS-6 in the KV-2 turret.Side view of the KV-2 with the 107 mm gun.
Source: CAMO 38-11355-175Rear view of the KV-2 at the Gorokhovets proving grounds. Note that from this angle, no changes can be seen.
Source: CAMO 38-11355-175
Trials
The tank arrived at the Gorokhovets proving grounds on 25 June, and the trials began. The ammunition used had additional explosive charges, increasing the muzzle velocity to 840 m/s. In total, 618 shots were fired, but the increased charges caused several issues. After 315 shots, the gun rammer broke. After 486 shots, the accuracy decreased considerably. The commission blamed these issues on barrel wear caused partly by the increased muzzle velocity of the shells. On the other hand, penetration was excellent. It penetrated 120 mm armor plates thick armor plates angled at 30° from 1,600 meters.
V.G. Grabin (white) at the trials of the KV-2, June 1941.Still from the video above, showing the KV-2 firing the ZiS-6.
The End
The damaged gun was transported back to Gorky, where it was repaired. By 10 July, Plant No.92 had already completed four additional guns, as well as having 214 guns in various stages of production.
There was still no sign of any tanks for Grabin’s gun. The truth was that work on the KV-4 had completely stalled after May. Regarding the KV-3 and KV-5, work was continuing timidly. The KV-3 had a full scale mockup and most blueprints ready, while the KV-5 was still just entering the blueprint stage. Given the circumstances, the GABTU altered their request, asking for just 35 ZiS-6 guns, 5 in October, 10 in November and 20 in December.
The start of the war on 22 June significantly affected these projects, with LKZ having to ramp up KV-1 production, as well as focusing on repairs of tanks. The situation aggravated when German forces were approaching Leningrad in August, and thus the SKB-2 design bureau was evacuated to the ChTZ, in Chelyabinsk. While the KV-4 and KV-5 were outright canceled, plans of continued work on the KV-3 lingered. Eventually, by the end of 1941, it was obvious that nothing would come out of it either.
Realizing his mistake of prematurely starting production of the gun, in July, Grabin pitched the idea of fitting it on the KV-2 directly, but this went nowhere, as KV-2 production had already ended the previous month. In September, he proposed the ZiS-6A, a system similar to, if not directly for, the KV-4, with a coaxial 45 mm 20-K gun. This went nowhere as well.
Despite Grabin’s victory in his personal vendetta with the tank designers, his disappointment over the situation was considerable:
“The production of the ZiS-6 increased daily. But there was still no sign of the tanks for which the gun was intended. Even after the beginning of the war, the Kirov plant did not deliver a single tank. The lack of the new tank forced us to limit production and eventually cancel it. It is difficult and embarrassing to write about this, in those days when everything that could shoot, even museum pieces, were sent to the front, around 800 gun barrels had to be sent back to the melting furnace”
—V.G. Grabin
The story of the ZiS-6 does not end here. It was used to develop some even larger 107 mm guns, like the ZiS-24, but this gun also suffered a similar fate in spring 1942. More importantly however, the ZiS-6 was remembered in February 1943, when the Tiger appeared. Stalin called Grabin once again, who assured that he could produce the ZiS-6 in 15-20 days. However, nothing materialized.
The fate of KV-2 with serial number B-9680 is unknown, as it was last mentioned as being in Plant No.92s stock in September 1941.
Conclusion
The KV-2 107 mm testbed proved that there were several issues with the ZiS-6 gun, and Grabin’s confidence to start production prematurely would be a mistake. The gun still needed refinements, and eventually, the heavy KV tanks which were meant to mountmount it were canceled with the outbreak of the war.
KV-2 with 107 mm ZiS-6, ilustration by Pavel Alexe.
KV-2 with 107 mm ZiS-6 testbed Specifications
Dimensions (L-W-H)
6.95 (hull) x 3.32 x 3.25 (m)
Total weight, battle-ready
>52 tonnes
Crew
6; commander, gunner, 2 loaders, driver, radio operator
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 heavy tank program was born from the perceived need for a much more powerful heavy tank than its predecessors. It was designed at the SKB-2 design bureau via a thorough competition. Thus, several different versions were proposed, including the one by G.N. Moskvin. Although the tank had a very traditional design, his design was not rewarded in the competition and forgotten. Nowadays, it is playable in Wargaming’s ‘World of Tanks’ video game.
KV-4 by Moskvin, as represented in World of Tanks. Though several details are missing or inaccurately modeled, it offers a good overall perspective on its design. Source; in-game screenshot
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The development of the Soviet KV-4 heavy tank, designated as Object 224, began in March 1941. The development of a 90-tonne German tank was reported in a letter from the Soviet Intelligence Services on 11 March 1941, which alarmed the Soviet military officials, leading to the GABTU requesting the development of a new super-heavy tank. The KV-4 was to weigh 70-72 tonnes, be armed with the 107 mm ZiS-6 in the turret, and have 130 mm thick armor at the front and 120 mm towards the sides and rear. The deadline for the tank design was set to 17 July 1941, with the prototype building and armament testing set for October of the same year.
However, on 7 April 1941, the GABTU revised their requests, raising the weight to 75 tonnes and the armor thickness to 135 mm at the front and 125 mm towards the sides and rear. The blueprints’ deadline was also narrowed to 15 June 1941. At the same time, the KV-5 was requested, a tank that would weigh at least 90 tonnes, have 170 mm of armor at the front, and 150 mm at the sides. Additionally, the KV-3 was ‘revived’ and improved to fulfill a stopgap role until the KV-4 and KV-5 tanks were ready for production.
At LKZ (Kirov Leningrad Factory), the SKB-2 design bureau began work on the KV-4 on 10 April 1941. The head of the project was J. Y. Kotin, who created a competition between the SKB-2 engineers, with the top few designs receiving financial rewards. Over 20 engineers competed, submitting over 20 individual designs. The winning design was that of N. L. Dukhov, which was essentially an enlarged KV-220. Second place went to the K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin trio, who submitted a tank with the main gun in the hull and secondary gun in a small turret. Third place went to N. V. Tseits, who submitted a tank with a very low hull but large turret to offset the lack of hull space.
Despite the efforts put into the development of the KV-4, it never saw production. The outbreak of World War II on 22 June 1941 disrupted the Soviet tank development program, and the resources were redirected to immediate production of already existing designs. Additionally, the heavy losses suffered by the Soviet army during the initial stages of the war showed that the development of heavy tanks was not a priority. The KV-4 project was eventually canceled, and the KV-3 was abandoned as well, with the resources redirected to the development of the IS series of tanks.
G.N. Moskvin
Born in November 1909 in Nizhny Novgorod, Grigory Nikolaevich Moskvin began working at a waterway administration and later at the Svetlana Plant. In 1931, he was drafted into military service, and shortly thereafter was assigned to the design bureau of the Artillery Institute (SKB-4) at the Leningrad Kirov Plant. There, he would work on various self-propelled gun systems, such as the SU-14, SU-5 series of SPGs, SU-6 and armament system of the T-111 tank. He also worked on the design of tanks at Plant No.185, but was fired due to his brother’s arrest. In 1940, Moskvin was hired by the SKB-2 heavy tank design bureau. Here he worked on the T-50 light tank, KV-220, KV-4, and, after SKB-2s transfer to ChTZ and the start of the Second World War, he worked on the KV-7, KV-13, SU-152, and ISU-152. He also participated in the design of the well-known ‘pike nose’ of the IS-3 heavy tank. After the war, he worked on heavy tank armor, as well as other projects, such as the Object 740/750 and PST-54. Prior to his retirement in 1972, he worked on the development of the Lunokhod lunar rover project. He later passed away in 1986, aged 77.
Moskvin had been awarded the Order of Lenin, The Stalin Prize, Order of the Patriotic War and Order of the Badge of Honor.
G.N. Moskvin in 1943. Source: TiV No.11 2013
Design
Unlike most other KV-4 designs, Moskvin provided detailed drawings of his design, from all relevant angles. The tank was to weigh 101 tonnes on paper, being 9.573 meters long, 4.03 m wide and 3.74 m tall.
The tank had a standard layout, with the turret in the center and the powerpack in the middle. The hull was akin to most previous KV tanks, with a stepped front plate, flat sides, and a large engine deck, with its unique engine cooling system vent at the rear.
The main turret was very large, to be able to accommodate both the large main gun and the secondary turret, mounted at the rear of the turret. Ammunition was stowed underneath the main turret ring, for both the main and secondary guns.
The mantlet was mounted over the frontal curved turret plate and protected by two ‘fins’ on either side, protecting the internal mechanism from outside elements. The side walls were curved, offering great effective protection frontally, with small arm firing ports in the center. The secondary turret had a cupola with an unspecified amount of periscopes, for clear battlefield vision.
The engine was a 1,200 hp M-40 aviation engine, boosted with the help of four TK-88 turbochargers. It was connected directly to the final drives and sprockets, at the rear.
Blueprints of Moskvin’s KV-4 design, with a cutout view of the interior from the side, and top view of the hull interior Source: Stalin Supertanks IS-7Front view of the tank, as well as a cutout of the front and top of the turret. Source: Stalin Supertanks IS-7
Crew
The crew likely consisted of 8 men, commander, main gunner, 2x main loaders, secondary gunner, secondary loader, driver, and bow machine gun/radio operator.
The gunner sat in the front of the turret, to the left side of the gun, and the commander sat right behind him. The two main loaders were seated on stools slightly facing the gun, on its right side. From here, the loader in the front could pass on shells from the front side wall or hull, while the rear loader could operate the breech and load the shells. Behind the gun breech, the two crewmen for the secondary turret were seated, gunner and loader. They were seated on either side of the 45 mm gun with enough clearance from the main gun breech.
In the front of the hull, the driver and radio operator had their positions. The latter would operate the flamethrower, while the driver operated the ball-mount machine gun.
Armament
The main armament was the 107 mm ZiS-6 gun developed at Plant No.92 by V.G. Grabin in early 1941. It was specifically developed to be fitted on the KV series of heavy tanks. It offered excellent anti-tank capabilities, with an alleged penetration of 120 mm angled at 30° from 1,600 meters. The shells were 120 cm long and weighed 18.8 kg.
Secondary armament was the 20-K 45 mm gun mounted in the secondary turret, as well as 2 or 3 DS-39 7.62 mm machine guns which were mounted in ball mounts and coaxially. A flamethrower was also mounted in the front of the hull. These secondary weapons offered, on paper, adequate offensive power against both soft-skin vehicles and infantry.
Armor
The massive 101 tonne tank was very well protected for its time. The front hull and turret plates were 130 mm thick, while the side and rear plates were 125 mm thick. The secondary turret was also 125 mm thick all around, offering great protection at the cost of a very cramped interior.
Fate of the project
After the announcement of the competition winners, work on the KV-4 did not progress any further. Engineers from SKB-2 shifted their attention to the design of the KV-3, with a full-scale mockup of it built. In June, work on the KV-5 also began, based on the winning designs of the KV-4, hence why its appearance was similar to that of the KV-4 by N.V. Tseits.
However, with the start of the war, the LKZ plant had to focus on the realities of war. More KV-1 tanks had to be built, and large numbers had to be repaired. As such, work on these super heavy tanks slowed down. The situation turned sour in August and September, when German forces were advancing towards Leningrad and the SKB-2 design bureau was transferred to ChTZ in Chelyabinsk. The heavy KV designs were left behind and never brought up again. Only the KV-3 was still being discussed, but it eventually faded away as well.
Conclusion
The KV-4 heavy tank program was born as a counter to the elusive German heavy tank developments (specifically the Löwe) which themselves hardly materialized. While the nature of development via competition brought up innovative features, the realities of the situation and the start of the war required the Soviet tank industry to focus on realistic targets. The Soviet tank arsenal was heavily outclassed across most elements, and while propagandistic stories of the T-35 and KV-1 shined, their unreliability and lack of combat effectiveness led to the need for better heavy tanks. The even heavier KV-4 was certainly not the answer.
KV-4 by G.N. Moskvin, ilustration by Pavel Alexe.
KV-4 Moskvin Specifications
Dimensions (L-W-H) (approx.)
9.573 x 4.03 x 3.74 m
Total weight, battle-ready
101 tonnes
Crew
8 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3x DS-39 7.62 mm machine guns
Flamethrower
Armor
Front: 130 mm
Sides: 125 mm
Rear: 125 mm
Roof & belly; 50 mm
Rozanov’s Destroyer Tank of Heavy Type. Illustration by Pavel Alexe.
Soviet Union (1944)
Heavy Tank Destroyer – Drawings Only
The efforts and hardships that nations endure during war, both military and civilian alike, are often tied with compassion and the patriotic will to help out. This also included the design of tens, if not hundreds, of drawings and proposals of tanks and armored combat vehicles made by civilians and soldiers. This happened in the USSR during the Great Patriotic War, where many, in most cases without any studies in engineering, submitted designs to the Soviet authorities during the war. Most of these designs, colloquially known as ‘napkin drawings’, were complete nonsense in terms of practicability, military value, industrial capabilities, and the laws of physics. But a rifle platoon commander, Lieutenant L.V. Rozanov proposed perhaps one of the more sensible of such designs, without sacrificing any ingenuity and creativity. His tank would feature heavily sloped armor plates, powered frontal sprockets, and other curious features. Despite his efforts, Rozanov’s tank was never considered by the Soviet military.
Development
During March 1944, a rifle platoon commander, part of the 17th Independent Reserve Officer Regiment, Lieutenant L.V. Rozanov would go beyond his duties as an infantryman and submit to the GABTU (Main Directorate of Armored Forces) his design for a ‘Destroyer Tank of Heavy Type’ (Rus. Танк-истребитель тяжёлого типа’, or ‘ТИТТ’ for short). Out of the many AFV designs proposed by Soviet soldiers and officers, Rozanov’s design surpasses many of them. This is largely thanks to Rozanov’s engineering degree and his 7-year technical work experience prior to the war. He would submit his design to the GABTU in June 1944, and later to the Main Artillery Directorate of the Red Army (Rus. Главное артиллерийское управление Красной Армии, in short ‘GAU KA’).
Feedback was not so complimentary. According to the experts, the rollers in the front of the tank could greatly reduce the maneuverability of the vehicle and increase its combat weight. Sloped spaced armor plates on the sides could lead to an increase in size and complicate the maintenance. In addition, they claimed that it did not protect the tank from driving over landmines.
The scheme of automatic loading of the gun drawn up by the inventor aroused much more interest. Judging by the fact that there is no blueprint of it in the archive file, the drawings must have been handed over to the higher authorities for further studies.
Drawing showing the general appearance of the tank. The folded infantry panels and front rollers counterweights are clear here. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554
Design
It is important to keep in mind that, like for lots of other patent(-ly absurd) proposals, many aspects of the vehicle’s design – gun model, armor thickness, hull size, elevation arcs, crew positions, etc, – were not precisely described by Rozanov. Since the Rozanov’s Destroyer Tank was definitely inspired by T-34 and was highly likely either a deep modernisation or even a probable future substitute for it, these two vehicles will be often looked at together from now on in this article. The author’s blueprints also use T-34’s dimensions and, partially, a layout, as a basis.
Hull
The hull itself was relatively standard, heavily inspired from the T-34 medium tank layout, with more pronounced angles for improved protection. The upper frontal plate went far beyond the frontal drive sprockets, and instead stopped above two large rollers. On the sides of the upper hull, foldable shields were given so that infantry would be protected from the front and sides from light arms fire, shrapnel and dirt. The shields would fold in three stages. The main plate would stand vertical, and offer side protection. A smaller plate hinged to it would fold outwards. Lastly, a third plate, hinged on the front-end of the main plate, would lock in place with the frontal hull plate and thus provide frontal protection. While such a design feature is an odd one in tank design, it must be remembered that the Soviets made heavy use of tank-riding infantry going into battle, the so-called Tankodesantniki.
Side view of Rozanov’s heavy tank compared to a human, around 170 cm in height. Note the extent the hull protrudes over the front drive sprocket. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554Top view of Rozanov’s design. The odd turret roof layout is clear. The engine deck and rear hull plates are bare, but these would have housed engine cooling outlets as well as exhausts on the finished design. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554
Turret
The turret, although small, was very advanced in design. The front was made out of a flat plate angled at 58°, while the rest was circular and heavily angled 58° from horizontal and 55° at the sides and rear. It had a triangular protrusion along the top of the turret, which would allow for the gun to depress along with the autoloading mechanism. There were two service hatches on either side of the gun protrusion for the two crew members. The turret was very low and would not fit the crew members, but rather just their heads and parts of their torso.
Original front view of the proposal. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554
Armament
The gun was to be equipped with a 16-shot belt-style autoloader, but as Rozanov understood the complexity and unreliability of such a system, the gun could be loaded manually. The autoloader would rotate around a square shape, and could be manually reloaded with either AP or HE-FRAG shells. Neither the model, nor even caliber of the gun were defined by the author of the proposal.
Back in 1944, it seems that the 85 mm ZiS-S-53 was the only possible main armament, which can be deduced rather clearly. The S-53 gun had a simple design, compact size, and was quite reliable at the time. It would have even fit in the tight turret of Rozanov’s Destroyer Tank with an internal gun cradle. Other variants seem less preferable. The production of the 85 mm tank gun D-5T, a possible analogue of the S-53, ceased on 1st March 1944. By the time Rozanov’s tank would have gone into mass production, it would no longer have been available. Guns of smaller caliber would have been less powerful, and the vehicle would hardly have fulfilled its role as a ‘Destroyer Tank.’ On the other hand, guns of larger caliber would have exacerbated problems with recoil, elevation and depression arcs. Moreover, the turret would have become tighter, and it would have likely been impossible to fit an autoloader.
85 mm ZiS-S-53
APHE
APCR
HE
BR-365A
BR-365K
BR-365P
OF-365K
9.2 kg
4.99 kg
9.54 kg
792 m/s
1050 m/s
793 m/s
0.164 kg TNT
0.048 kg charge
(0.07392 kg TNT eq.)
–
0.66 kg TNT
142 mm pen
145 mm pen
194 mm pen
–
7-8 rpm
Parameters of penetration are given for 0 m and 0°.
Though Rozanov never defined the exact model of the gun to be used on his tank, 85 mm ZiS-S-53 would highly likely have been the choice if it ever entered mass production.
(source — ZA DB, Pablo Escobar’s gun table)
Running Gear
The most unusual features of the tank concerned its running gear. The tracked portion featured seven small roadwheels, likely sprung by coil springs within the hull, though this is not confirmed by any drawings. The sprocket was at the front and the idler at the rear. For the return track, four small return rollers were held up by pins attached to the sideskirt hinge.
Side view of Rozanov’s tank showing several details, including the roller’s arm with chain drive and spring suspension. The sideskirt is also in the folded position, allowing for a view of the return rollers. Likewise, the infantry flaps are in the upward position. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554
The frontal rollers were attached on both sides of the front of the track, at the bow of the hull. They either used solid rubber or steel for grip. To attach them to the hull, a large arm would run alongside the hull wall, pivoting in the drive sprocket’s position. From here, a chain from the drive sprocket was pulled to the roller for power. On the opposite side of the arm, two large springs, one above and one below, would provide stiffness to the roller arm. At the tip of the arm, a counterbalance was added to prevent the roller from hopping around violently on poor terrain, suggesting that the roller itself was not particularly heavy.
The rollers were meant to offer protection for the front of the track, as well as allowing the tank to be far longer without having a longer track. A bonus was mine protection, as the potential mine would be detonated by the roller, well in front of the crew compartment, though the tank would still be heavily damaged.
Scheme of Rozanov’s tank front roller layout, based on original blueprints. Instead of Rozanov’s indefinite gun silhouette, 85 mm ZiS-S-53 is used, as well as a more realistic rear transmission (therefore, the turret was moved forward). Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.
Although the rollers were meant for protecting the rest of the tank, they themselves were of a frail construction. The chains were susceptible to damage and would likely fall off frequently, removing the steering capability. This in turn would greatly harm the tank’s pivoting performances, due to the rollers being mounted so far forwards.
Since the vehicle was proposed as a deep modernization/analogue of T-34 medium tank, it would have probably received the same engine, V-2-34, with power output up to 450-500 hp.
Protection
Not much is known about the raw armor thickness of the tank plates, but they were heavily sloped. The upper frontal plate was angled at 32° from horizontal, while the upper rear plate was angled at 29° from horizontal. The upper side armor was angled at 45°, angled inwards. The sideskirt, running across the length of the running gear and lower hull, was also angled inwards at 45°, forming a hexagon shaped hull, from both the front and side views. Behind the sideskirt was the track, return rollers and flat hull wall, which was thinner in armor thickness.
Partial cutout of the tank, seen from the front. Note the side infantry shields in open position, as well as the left sideskirt open for maintenance. Source: TsAMO RF, Fund 38, inventory 11350, case No.1554;
The turret was surprisingly ahead of its time as well. It was entirely circular, with the exception of the frontal plate, which was flat but angled at 58° from horizontal.
Armor scheme of the Rozanov’s tank, based on original blueprints. Simple 16-shot belt loader is a substitute for lost Rozanov’s original concept. Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.
Crew
Since none of Rozanov’s schemes or blueprints of the vehicle’s crew positions are yet known (and highly likely they never existed), it can only be hypothesized with available Destroyer Tank data and the inner layout of the T-34 medium tank. The crew likely consisted of three or four: commander, optional loader, gunner, and driver.
Front transmission, proposed by Rozanov, would hardly be possible on this vehicle, as it would leave almost no space for the driver. If the vehicle hull’s dimensions are considered similar to the T-34’s, the turret could accommodate up to three crewmembers.
Hypothetical inner layout scheme of the Rozanov’s tank, based on original blueprints, with all aforementioned revisions implemented. Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich;
Fate
By spring 1944, Soviet tank designers were working on new generations of tanks. In terms of medium tanks, the T-34-85 was dominating the Soviet scene, while the T-44 was conducting trials. Regarding heavy tanks, the IS-2 had entered service, and designers were already working on developing its proposed replacement, the IS-6 and later IS-3 and IS-4. Naturally, there were many other designs and projects scattered across the Soviet design bureau’s drawing boards, but one can appreciate that the bar was set high by the seemingly promising T-44 and IS-6.
Additionally, the situation on the frontline was looking better and better. Soviet forces were making progress and were able to retake former territories.
These factors made it harder and harder for unconventional designs to be considered by the GABTU, as there was no longer a dire need for a ‘miracle tank’, but rather the reliability and trustworthiness of a proven platform, such as the T-34 and IS.
Around June 1944, Rozanov’s tank project was evaluated by the head of the 8th Department of the Technical Directorate of the GABTU, Engineer-Lieutenant Colonel Frolov, and several reasons were given for why the project was not considered.
Firstly, he stated that the rollers would decrease the tank’s traverse capabilities, while adding extra weight to the vehicle without any load bearing capacity. While this is true, the wheels were powered by the sprocket, and would turn along with the tracks. Perhaps the bigger disadvantage with this mechanism was the added complexity and maintenance required to use the vehicle.
Secondly, Frolov was not a big fan of the inwards-angled sideskirts, which he claimed complicated access to the track and running gear as well as the roller suspension system. He also claimed that the sideskirts would not help with mine-resistance, which is true, as they were too far away from any crucial components.
Through a modern analysis of this design, and with the luxury of hindsight, many of the features proposed by Rozanov would be implemented in some form or another in real projects. The angled sideskirt armor would be incorporated on the hull design of various post-war heavy tanks, most notably the IS-7 series, while the low, circular turret would prove an iconic signature of many post-war Soviet tanks and IFVs.
With that, the project was dead and would not be revived, and like many such designs, would remain forgotten for 70 years until it was scanned by modern researchers. It has gained popularity with its introduction into the online game World of Tanks, under the name TITT Rozanov.
Rozanov’s Tank in World of Tanks
The game version, presented in Wargaming’s World of Tanks, differs from its real counterpart in several important aspects.
‘TITT Rozanov’ as presented in World of Tanks. Note that some essential parts of the design are missing: the gun cradle, muzzle brake, etc. The front wheels are fixed in the topmost position. Source: WoT Express
The most striking difference is the armament. Instead of a compact-sized 85 mm S-53, the game developers installed the 85 mm N-3-457, a version of the high-power 100 mm D-10 anti-tank gun. The development periods of this gun and Rozanov’s tank never intersected in real life.
85 mm D-10-85
AP
APCR
HE
BR-365M
BR-365P
OF-365K
9.4 kg
4.99 kg
9.54 kg
1053 m/s
1313 m/s
800 m/s
–
–
660 g TNT
231 mm pen
263 mm pen
24 mm exp. pen.
4-5 rpm
Parameters of penetration are given for 0 m and 0°.
Parameters of the D-10-85 high-power anti-tank gun. N-3-457 had similar ballistics.
Source: ZA DB, Pablo Escobar’s gun table;
More than that, several important parts of the gun’s construction are missing: the muzzle brake and the gun’s cradle (while creating the vehicle, Rozanov tried to reduce the inner volume of the turret as much as possible; therefore, he decided to put it outside). Wargaming’s version has serious problems with the turret’s inner space, as it needs to accommodate a large gun’s recoil distance and breech, as well as the aforementioned gun cradle.
SU-100 with D-10-85 gun, also known as SU-D-10-85. Source: M. Svirin, M. Kolomietz, ‘Soviet self-propelled artillery in 1941-1945’
Generally, the game version of Rozanov’s tank differs from its real prototype greatly. Insead of ‘up-armored T-34-85’, game developers created a full-fledged analogue of the T-44 medium tank. Still, they tried to adhere to the author’s vision of the vehicle’s battle role (‘destroyer tank of heavy type’) and made a slow, heavily armored medium tank with rather powerful armament.
Conclusion
Hypothetical appearance of serial Rozanov’s tank. Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich;
Even though Rozanov’s proposal was innovative and had several forward-looking features, semi-automatic gun, front rollers, ‘minesweepers’, spaced armor, etc., it was too complicated for the Red Army to produce, and therefore never left the drawing board. At that time, the T-44 medium tank was entering mass production. Albeit a more traditional layout, it fulfilled objectives similar to ones laid out by Rozanov in his Destroyer Tank.
Rozanov’s Destroyer Tank of Heavy Type. Illustration by Pavel Alexe.
Rozanov’s Tank Specifications
Dimensions (L-W-H) (estimated*)
6.680 x 4.050 x 2.070 m
Total weight, battle-ready
Unknown
Crew
3 men (Commander, gunner, driver)
Propulsion
Unknown; V-2-34 probably
Speed
Unknown
Suspension
Torsion bar, 7 wheels per side + 1 roller per side
Armament
Unspecified gun w/ 16 round autoloader;
85 mm ZiS-S-53 probably
Armor (estimated*)
70/100/30 mm (turret)
70/60/70 mm (hull)
No. Built
0, blueprints only
* – Estimations are for +/- T-34-sized vehicle, based on Rozanov’s original schemes;
KV-4 (Object 224) Buganov. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
In spring of 1941, the Soviets were working on KV-1 replacements of various sizes and weights, from the moderate upgrade T-150, to the much larger KV-220. But rumors of German super heavy tank projects catalyzed the development of a variety of even larger heavy tank projects, one of them being the KV-4. Its development consisted of a tank design competition, in which engineer K.I. Buganov participated. His unusual proposal was appreciated and was awarded sixth place in the competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The Soviet Union was caught off guard in 1941 when intelligence reports revealed that Germany was developing a 90-tonne heavy tank armed with a 105 mm gun. The Soviets realized that their existing heavy tanks, the T-35 and the KV-1, were not enough to match the German threat. Work on developing heavier tanks commenced, and on 21 March 1941, the GABTU sent requirements to LKZ for the development of the KV-4, designated Object 224.
The KV-4 was required to be a 70-72 tonne heavy tank armed with a 107 mm ZiS-6 gun, a secondary 45 mm 20-K gun, and at least three DT machine guns. Armor was to be 130 mm at the front and 120 mm towards the sides and rear. Propulsion was to be provided by a 1,200 hp M-40 engine, also developed at LKZ, and the crew was to consist of six. The deadline for the blueprints was set for July 17, 1941.
On 7 April, the GABTU completely redesigned their request, introducing two new heavy tanks, the KV-3 (Object 223) and KV-5 (Object 225). The KV-3 was based on the previous KV-220, but with thicker 120 mm armor and the larger 107 mm ZiS-6 gun. It was intended as a stopgap vehicle, until the KV-4 and KV-5 were ready for production. The KV-5 was an even larger heavy tank, weighing at least 100 tonnes, and with armor of 170 mm at the front and 150 mm at the sides and rear. The KV-4, to better fit in between these two tanks, was also edited, with side and rear armor increased to 125 mm and weight threshold increased to at least 75 tonnes.
Work on the KV-4 began on April 10, 1941, with J. Y. Kotin as the head of the project. Kotin set up a competition for the tank’s design, encouraging engineers to come up with original and innovative features. Over 24 engineers submitted more than 20 individual designs, and the winning design was that of N. L. Dukhov. Second place went to K. I. Kuzmin, V. I. Tarotko, and P. S. Tarapatin, who designed a tank with the gun mounted in a central rotating sponson, with a smaller turret on top. Third place went to N.V. Tseits, with a more conventional design, featuring a very large turret and low-profile hull.
Work on the KV-4 stagnated after the end of the competition and was further delayed by the German invasion of the Soviet Union in June 1941. Despite this setback, the project was still active, but most of the focus had shifted to the KV-5, which was being developed by the winners of the KV-4 competition.
One of the designs submitted was by SKB-2 engineer K.I. Buganov. His tank’s unique and unorthodox features allowed his proposal to receive the sixth place prize of 1,000 rubles.
K.I. Buganov
K.I. Buganov began his military engineering career at the Experimental Design Machine-Building Department (OKMO), working on earlier Soviet tank designs, such as the T-28 and T-35, and in the late 1930s was transferred to the SKB-2 design bureau. After 1951, Buganov worked under Kotin at the Special Design Bureau of Heavy Tanks, as head of the hull and armor testing section, and in 1952, as part of VNII-100, he was chief-designer of the Object 907 medium tank.
Unfortunately, no further information on K.I. Buganov could be found publicly.
Design
The design presented by Buganov for the KV-4 was all but conventional. The engine and final drive were moved to the front, as opposed to the other KV tanks, and the main turret was moved to the rear, with the secondary turret on top. Furthest back were the fuel tanks.
To allow for a narrower hull but still a large turret, the turret had ‘lips’ protruding from either side of the hull, allowing for full 360° rotation. The main turret shape was peculiar as well, resembling a disk segment, with heavily sloped turret cheeks on either side.
The secondary turret was mounted on the right side of the main turret, and was of an usual design, akin to that of the T-50 light tank. It was capable of full 360° rotation, independent of the main turret.
Due to the narrowness and shortness of the hull, the engine bay area was exceptionally small. Thus, the entire air cooling and intake systems were moved into sponsons on the sides of the hull.
The ammunition was stowed both horizontally and vertically at the bottom of the fighting compartment, starting from the engine bay firewall, all the way through to the fuel tank.
Side and top cross-view of Buganov’s KV-4 design. Note the bizarre shape of the turret. Source: Yuri PasholokFront view of Buganov’s KV-4 and a cross-section of the engine bay, showing the cooling system sponsons. Source: Stalin Supertanks IS-7
Crew
The only information provided regarding the crew is the number, six n. However, due to the peculiarities of the design, it is challenging to accurately assign what roles these six crew members had, and where their exact positions were.
One hypothesis is that the crew consisted of a commander, main gunner, main loader, secondary gunner, secondary loader, and driver. The main gunner and commander would have been to the left of the gun, while the secondary gunner and loader would have been high in the secondary turret. The main loader would have been underneath the secondary turret, with ample access to the ammunition stowage below. The driver would have sat alone in the hull’s front and driven the tank, as well as fired the ball-mounted DS-39 machine gun.
Another theory is that the commander was also the gunner of the secondary turret. This would have given him an excellent view of the battlefield, but burdened him with the task of also aiming and firing the secondary gun. The sixth crew member in this case would be the radio-operator/bow machine gun, seated on the right side of the hull, opposite to the driver.
Armament
Much like the other KV-4 designs, the tank was armed with the new 107 mm ZiS-6 (F-42) gun, developed at Plant No.92 by V.G. Grabin in late 1940, early 1941. It was first tested on a tank platform on a specially modified KV-2 in June 1940, where it proved to be a formidable anti-tank weapon. It fired a 120 cm, 18.8 kg shell at 800 to 840 m/s, penetrating 115 mm of armor at 1,000 m.
The secondary armament consisted of a single 20-K 45 mm gun and 3x DS-39 7.62 mm medium machine guns, one in the hull (ball-mounted) and one mounted coaxially to each cannon.
The 20-K, though older in design, was still one of the most common guns used on Soviet armor, in tanks such as the BT-series fast tanks, T-26 and T-50 light tanks, or T-35 heavy tanks. Though comparatively obsolete by 1941 as an anti-tank weapon, as proven by the aforementioned tanks in the first stages of Operation Barbarossa, it was still a viable weapon against infantry and soft skin vehicles.
Armor
The hull was built out of 125 mm thick armored plates, stamped into shape, like on the rounded portion of the front, covering the transmission and final drive. The sides and rear were equally thick. The front of the main turret was 140 mm thick, with the cheeks angled outwards, angled at 45°. Less critical areas such as the hull belly and hull/turret decks were 50 mm thick.
Fate of the Project
After the competition had ended in May, nothing new was documented regarding the KV-4. Instead, most work shifted towards developing the KV-5. Things took a turn for the worse with the Axi’ invasion of the Soviet Union. As a result, LKZ had to shift focus from prototypes to KV-1 tank production and repairs. Nonetheless, work on the KV-5 still continued until August, when German forces began approaching Leningrad, home of LKZ. Consequently, the SKB-2 design bureau was disbanded and members were moved to ChTZ in Chelyabinsk. Aside from a few select projects, most tank programs were left behind, including the KV-4 and KV-5.
Conclusion
Born around the fear of German tank rumors, the KV-4 tank program was very short-lived and arguably a large waste of efforts and resources. Yet its circumstances, oversize proportions and capabilities, and, most importantly, the original tank design competition make it one of the more fascinating Soviet tank programs of the period. Buganov’s entry for the competition was in no way less peculiar, with a very bizarre approach in overall layout and using a variety of quirky features. For these ‘accomplishments’, he was awarded sixth place.
KV-4 (Object 224) Buganov. Illustration by Pavel Alexe.
KV-4 Buganov Specifications
Dimensions (L-W-H) (approx.)
7.7 x 3.8 x 3.32 m
Total weight, battle-ready
83 tonnes
Crew
6 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
50 km/h (hypothetical)
Suspension
Torsion bar, 8 wheels per side
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
3x DS-39 7.62 mm machine guns
Armor
Hull: 125 mm
Turret front: 140 mm
Turret rear: 110 mm
Top & belly: 50 mm
KV-4 Pereverzev variant with a shorter turret. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
Based on rumors of German heavy tank developments, the Soviets expanded their heavy tank programs in the spring of 1941. One of these projects was that of the KV-4, which entailed a competition among several designers from the SKB-2 design bureau. One of these proposed designs came from military engineer L.N. Pereverzev, who proposed a massive 100-tonne tank, with several unique features, such as tracks returning over the entirety of the hull. For his efforts, he was awarded 7th place in the competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
In early 1941, the Soviets were experimenting with KV-1 based tanks with increased armor and firepower, ranging from the T-150, which was essentially a KV-1 with 90 mm armor, to the KV-220, with 100 mm of armor, the 85 mm F-30 gun, and a longer hull. Other projects included the Object 221 and Object 222. The latter was set to enter mass production in July 1941, under the name KV-3. These tanks were designed and built at the LKZ (Leningrad Kirov Plant), by the SKB-2 design bureau.
Yet in a quick turn of events, on 11 March 1941, the Soviet Intelligence Services passed forward a report on the development of German heavy tanks. The heavy tanks Mark V, Mark VI and Mark VII were mentioned, weighing at 36, 45 and 90 tonnes respectively. The Mark VII, which can be assumed to have been an early proposal of the Pz.Kpfw.VII Löwe, greatly worried the Soviet officials. Aside from its heavy weight and supposedly thick armor, it allegedly was to be armed with a 105 mm gun.
If these German tanks were to become a reality, combined with the increasing threat of German invasion, the Soviets would have no realistic answer. The only true heavy tank in service at the time was the KV-1, and while it was adequately armed and very well protected, its weight, rushed development, and unreliable mechanics would make the KV-1 tank a problematic vehicle during wartime use. The heavier tanks, such as the T-150 and KV-220, relied on many of the KV-1’s components, with thicker armor and larger guns, while still failing to match the theoretical power of the new German heavy tank.
It was clear that a new heavy tank was needed, thus on 21 March, a new heavy tank was ordered to be developed at LKZ. Named KV-4, it was to be armed with the recently developed 107 mm ZiS-6 gun as well as a secondary 45 mm gun, several machine guns and a flamethrower. Armor was to be 130 mm at the front and 120 mm at the sides. Due to these measures, the weight of the tank was expected to be between 70 and 72 tonnes. To power this new heavy tank, a 1,200 hp M-40 aviation diesel engine with four TK-88 turbochargers was used. The SKB-2 design bureau at LKZ was tasked to develop the tank, which received index 224 (Object 224). The project deadline was 17 July.
Shortly thereafter, on 7 April, the heavy tank programs were reconsidered. Firstly, the KV-3 was to become a larger tank, based on the uparmored hull (to 120 mm) of the KV-220, with a new turret and the same 107 mm ZiS-6. The KV-4 was also changed, its side armor was increased to 125 mm, the weight estimate was increased to at least 75 tonnes and other small changes were made. Lastly, the KV-5 (Object 225) was to be designed, with the same 107 mm gun, but with 170 mm of frontal armor on a 100 tonne platform. Furthermore, the deadline for the KV-4 was brought forward to 15 June.
The head of the KV-4 project was head of SKB-2, J.Y. Kotin, but instead of appointing a design team, he would launch a design competition for the SKB-2 engineers. The goal was to incorporate as many original and innovative features as possible, and the best designs would be rewarded financially. With the funding and project approval from LKZ director I.M. Zaltsman, the competition began.
After evaluation, the results of the submitted designs were given on 9 May. Over a dozen different drawings and engineers partook. First place went to N.L. Dukhov, second to the trio of K.I. Kuzmin, V.I. Tarotko and P.S. Taraptatin. Third place went to N.V. Tseits. In total, 11 designs were awarded placements, with 13 designers receiving monetary prizes.
One of these awarded designs was by L.N. Pereverzev, whose design was ranked 7th, alongside the designs of Kalivod and Bykov. As an award for receiving 7th place, Pereverzev received 500 rubles.
L.N. Pereverzev
After graduating from the Military Academy of Mechanization and Motorization of the Red Army in 1939, Leonid Nikolevich Pereverzev started working as a military engineer at the LKZ SKB-2 design bureau. There, he would be involved in most of their projects, with the development of the KV-1, being chief engineer of the KV-150 and the gearbox designer for the KV-220, as well as partaking in the design of the KV-3 and KV-4. However, these would be his last tank design projects. In August of 1941, shortly after the German invasion, Pereverzev would be transferred to the newly formed 22nd PRB (Mobile Repair Battalion) at LKZ. Both he and his unit quickly received recognition for their skill in the repair and maintenance of KV-1 tanks.
By the end of the war, Pereverzev had received the Medal For Military Merit, Medal For Defense of Moscow, Medal For the Capture of Köningsberg, Medal For Victory against Germany in the Great Patriotic War of 1941-1945, Order of the Patriotic War (both I and II Degrees), and Order of the Red Star.
Leonid Nikolevich Pereverzev after the war. Source: Yuri Pasholok
Design
Of the two dozen KV-4 designs submitted, Pereverzev’s was one of the strangest. The turrets were arranged in a battleship-style layout, consisting of a smaller turret armed with a 45 mm gun in front of the main turret, armed with a 107 mm gun, allowing for good horizontal firing angles for both turrets. The engine, gearbox and final drive were located at the rear. The sprockets were extended far beyond the armored hull, in lightly armored housings, allowing for trench crossing capabilities, a design concept found as early as the British ‘tadpole tail’ found on the First World War Mark IV tank. This design choice allowed for a wider hull with more internal space, but greatly sacrificed the protection of the tracks, which had no cover over them and were susceptible to any kind of enemy fire.
The frontal hull section consisted of two main armor plates that were pressed into shape and welded together. The sides were more peculiar, as no drawings give a clear picture. Only the top cutout view drawing shows that the fighting compartment and fuel tanks were pushed underneath the track returns, protected by thick 125 mm armor. The rear consisted of the standard KV-style armor plates with room for air circulation for the cooling system.
Side cutout view of Pereverzev’s proposal, showing the track return riding over the hull, on small rollers. Note that the top machine gun turret had faded out. Source: ASKMTop cutout view of Pereverzev’s KV-4. On the top track, the sponson and subsequent sideskirts can be seen. Fuel and ammunition was stored here. Source: TsAMO
The tank was to be powered by a 1,200 hp M-40 aviation engine, which could run on both diesel and kerosene, and was boosted with four TK-88 turbochargers. The fuel tanks were mounted in the sides of the hull, and provided the tank with an estimated range of 15 hours of operation or 300 km. Its estimated top speed was 38 km/h.
Turrets
Like most KV-4 designs, Pereverzev opted for two turrets in a battleship-style configuration, with the smaller turret at the front, and the larger one on an elevated platform, allowing both to fire forwards without interfering with each other. Additionally, the main turret was mounted back far enough to provide a greater field of fire for the front turret.
One of the drawings also showcases two different turret designs, one with and the other without a turret bustle. A few other differences were made as well, like the removal of the rear-facing DT machine gun for more ammunition space in the turret bustle, and a new turret front armor plate construction.
The two different turret designs, the one on top showing a larger turret bustle and one-piece frontal section. The lower turret is shorter, and features a DT machine gun. Source: Stalin Supertanks IS-7
Crew
The crew was to be 7 men, consisting of the commander, 2 gunners, 3 loaders (1 for the secondary gun and 2 for the main gun) and driver.
The gunner sat to the left of the gun, and would fire the 107 mm gun. His vision was only provided by the main gun’s sight, as no other periscopes are drawn. The commander was seated behind him, and would operate the small rotating cupola, armed with a DT machine gun. Similarly, no periscopes are drawn in the blueprints, so his vision likely consisted of slits within the cupola. One of the main gun loaders sat to the right of the gun. In the turret variant without the turret bustle, he would also fire the rear-facing machine gun. The other loader likely sat in the hull, underneath the turret, and lifted the 107 mm shells to the other loader.
The driver sat in the front of the hull, in a station akin to the one on the KV-1. Behind him were the gunner and loader for the secondary turret.
Armor
Protection consisted of armor ranging from 105 mm to 125 mm on the hull, with the exception of the hull belly and decks, which were 40 mm and 50 mm respectively. The main turret had a 125 mm frontal plate, with the 125 mm thick mantlet taking up large amounts of space for extra armor. Sides and rear were 140 to 150 mm thick. The secondary turret had just 60 mm of armor at the front, due to the space constraints, but the sides and rear were 125 mm thick. The large size combined with the thick armor of the tank would have pushed its total weight to 100 tonnes.
Estimated armored thickness on Pereverzev’s KV-4, short variant turret. Source: Zinoviy Alexeev
Armament
The main armament consisted of the powerful 107 mm ZiS-6 (F-42) cannon, developed by V.G. Grabin at Plant No.92 for such heavy tanks, and was the main armament on all KV-4 designs. It had a muzzle velocity of 800 to 840 m/s and used an 18.8 kg shell, penetrating 115 mm of armor at 1,000 meters (calculated ballistics). In total, 108 rounds of 107 mm ammunition were provided.
Secondary armament consisted of the classic 45 mm 20-K mod.1937 gun, fitted on most Soviet light tanks at the time, and was a great complementary weapon, and still potent by 1941 against soft-skin targets. For the secondary gun, 195 rounds were provided.
Additionally, three (two for the turret-bustle variant) DT 7.62 machine guns were mounted, one coaxially with the 45 mm gun, one in the commander’s cupola and one at the rear of the main turret. In total, 3,000 rounds were given, in drum magazines.
The blueprints also mention a flamethrower with 100 liters of fuel, but where it was positioned is unclear.
Start of the war
After the competition results were announced in May 1941, progress on the KV-4 stagnated, focus shifting to the KV-5. The Axis’ invasion of the Soviet Union on 22 June 1941 further slowed down the development, as LKZ’s focus shifted to increasing production of the KV-1. The final nail in the coffin for the KV-4 and KV-5 came when the German troops were approaching the city of Leningrad, home of the LKZ plant. The SKB-2 design bureau had to be evacuated to ChTZ in Chelyabinsk, and the KV-4 and KV-5 projects were never continued, considering that the alleged German super heavy tank never appeared and the resources were better spent on more rational tasks.
Conclusion
Pereverzev’s expertise in tank design and as a military engineer was shown in his proposal for the KV-4 tank program, with several unusual features, such as the track running over the entire hull for more internal space and the extended sprocket for better trench crossing capabilities, as well as seeing the advantages of a turret bustle. For these attributes, his design was awarded 7th place in the design competition, but would not lead to any further work.
KV-4 Pereverzev variant with a shorter turret. Illustration by Pavel Alexe.KV-4 Pereverzev variant with a bustle turret. Illustration by Pavel Alexe.
KV-4 Pereverzev Specifications
Dimensions (L-W-H) (approx.)
9.5 x 3.8 x 3.82 m
Total weight, battle-ready
100 tonnes
Crew
7 (commander, main gunner, 2x main loaders, driver, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
38 km/h (hypothetical)
Suspension
Torsion bar, 8 wheels per side
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2-3x DT 7.62 mm machine guns
Flamethrower (100 liters)
Armor
Turret: 140 mm
Hull: 100-125 mm UFP
105 mm LFP
105-125 mm sides and rear
Top: 50 mm
Belly; 40 mm
KV-4 Ermolaev variant with 2 turret. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
During the spring of 1941, the Soviet SKB-2 heavy tank bureau was working on various types of heavy tanks, ranging from the uparmored KV-1, the T-150, to the super heavy KV-4 and KV-5 tanks. The development of the KV-4 entailed a new philosophy in which engineers would propose independent designs, in an attempt to bring out as many innovative features as possible. One of these designers was A.S. Ermolaev, who designed two KV-4 variants, one “standard” layout, weighing 90 tonnes, and one with a secondary turret, weighing 95 tonnes.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
The Soviet heavy tank project named KV-4, also known as Object 224, was developed during the early months of 1941. The development of the tank was triggered by a letter sent by the Soviet Intelligence services to the Soviet Main Directorate of Armed Forces (GABTU) in March 1941. The letter discussed the development of German tanks, including a 90-tonne heavy tank armed with a 105 mm gun. Realizing how far behind their heavy tank development was, the Soviets urgently began the development of a new heavy tank.
The Kirov Leningrad Plant (LKZ) and its SKB-2 design bureau were responsible for the development of the KV-4. LKZ had previously designed the KV-1, which was the only somewhat capable heavy tank in service at the time. However, the KV-1 proved to be unreliable, slow, and heavy during the war. LKZ had also designed several heavy tanks parallel to the KV-1 or as direct developments of it, such as the T-150, KV-220, and KV-3. The KV-220, in particular, was a capable design, comparable to the later German Tiger I heavy tank. It weighed 62.7 tonnes and was armed with an 85 mm F-30 gun, but it was cumbersome and unreliable during trials.
The KV-4 was requested to be a 70-tonne tank armed with the 107 mm ZiS-6 gun, a 45 mm Model 1937 or 1938 as a secondary gun, 3 DT 7.62 machine guns, and a flamethrower. The tank’s armor was to be 130 mm at the front and 120 mm at the sides. The tank was to be powered by a massive 12-cylinder M-40 engine with 4 TK-88 turbochargers that outputted 1,200 hp and had a displacement of 61 liters. The tank’s crew should have consisted of 6 members. The GABTU released the specifications for the tank just 10 days after receiving the letter, and the project deadline was set to 17 July. Plant No.92 was to build the guns by 1 September, and the Izhora plant was to finish the turret and hull by 1 October.
On 7 April, just 17 days later, the GABTU requested that the KV-4’s specifications be increased to 75 tonnes in weight and have armor improvements to 125 mm at the sides and rear. The deadline was also tightened to 15 June. In the same letter, the GABTU requested an even heavier vehicle, the KV-5, with 170 mm at the front and 150 mm at the rear, and a weight of 90 tonnes. Stalin’s personal involvement in the heavy tank projects and the sudden changes in design and increased time pressure would speed up the design process. The previously designed KV-3 was also given improved parameters, up to 68 tonnes, and armed with the same ZiS-6 107 mm gun as on the heavier tanks, with the purpose of acting as a stopgap tank.
To speed up the development of the KV-4, the SKB-2 design bureau head, J.Y. Kotin, set up a design competition. The competition was to gather as many diverse and revolutionary design elements as possible, and the top places were awarded financial rewards. Over 27 designs were presented by the SKB-2 bureau, and the first place was awarded to N.L. Dukhov, who presented an enlarged KV-220. Second place originally went to K.I. Kuzmin, V.I. Tarotko and P.S. Tarapatin, but were later disqualified because of the turretless design, and N.V. Tseits’ design (who was initially awarded third place) came second.
Ermolaev’s expertise in tank design and influence at SKB-2 landed his proposal in fourth place alongside Sychev’s design. For this achievement, he received 2,000 rubles.
A.S. Ermolaev
Born in the village of Kliny, Kaluga Oblast, in 1904, Afanasy Semyonovich Ermolaev would begin studying at the Military Academy of Mechanization and Motorization of the Red Army in 1932 and graduate two years later. He would then begin work at the SKB-2 design bureau at LKZ, working on the development of the T-28, SMK and KV-1. During the war, he would continue designing under Kotin’s leadership, working on the KV-1S, KV-85, IS, IS-2, SU-152, ISU-152 and ISU-122S. Post war, he would continue his activities at ChKZ in Chelyabinsk, working on several tanks, most notably the T-10, but also agricultural tractors K-700 and S-80.
He would receive 2x Order of Lenin, 2x Order of Kutuzov (1st and 2nd deg.), 2x Stalin Prize (1st and 2nd deg.), Order of the Red Banner of Labour, Order of the October Revolution, Medal “For the Victory over Germany in the Great Patriotic War 1941.1945” and the Medal “For the Defense of Leningrad”.
Afanasy Semyonovich Ermolaev after the war. Source: Famhist.ru
Design
Unlike most other designers, Ermolaev presented two variants for his entry, a traditional layout tank with one large central turret, and a longer tank with two smaller turrets.
Between the two variants, the hull was mostly identical. Following the general shape and layout of previous KV designs, the front featured a stepped plate which was pressed into shape, while the sides were completely flat. One difference was that the rear air cooling hole was protected by a flat armor plate instead of a curved one.
The main difference between the hulls of the two variants was the length, one was 8.22 meters long, while the other reached 8.52 meters, in order to fit the secondary turret. Both hulls had the same amount of roadwheels, but they were closer spaced on the shorter variant. Due to the various differences between the two, weight would also become a variable factor, with the single turret version weighing 90 tonnes, while the other weighed 95 tonnes.The main turret on both variants was remarkably similar, the only difference being the lack of a turret bustle on the two-turret variant. Otherwise, the turret was a hexagonal shape, made out of four different plates, where the side walls were stamped in shape. A large non-rotating cupola with six periscopes was located at the back of the turret and was used by the commander. No other details are shown regarding the turret.
Both variants were equipped with the 107 mm ZiS-6 and 45 mm 20-K mod.1937 guns, however they each were in their own individual turrets on the two-turret variant (the secondary turret had 270° rotation while the main full 360°), and mounted coaxially in the single-turret variant.
The variant with a single turret, which featured the 107 mm ZiS-6 and 45 mm 20-K mounted coaxially. Source: ASKMThe variant with 2 turrets, where the smaller turret was mounted in front of the main turret. Source: ASKM
The tank was powered by the M-40 1,200 hp aviation engine, capable of running on both diesel and kerosene. It was boosted by four TK-88 turbochargers. Fuel tanks were placed on the side walls. It was estimated that the tank could (optimistically) reach 40 to 45 km/h.
Crew
The single turret variant had a crew of 6 men; commander, gunner, 2x loaders, driver, and radio operator. The gunner sat to the left of the main gun, and operated both the 107 mm gun and 45 mm gun, which was mounted coaxially. The commander sat behind him, in an elevated position, with his head in the cupola, from where he could acquire targets and easily inform the gunner. The two loaders both sat on the right side of the gun, one tasked with loading the 107 mm gun and the other the 45 mm gun. The driver sat in the hull, in the center, with an emergency escape hatch in the floor, to his right. The position of the radio operator is unclear.
For the two-turret variant, the main gunner and commander had the same positions, while the two designated loaders for the main 107 mm gun sat on the right side of the gun, one loading the shells in the gun and the other lifting them from the hull stowage boxes.
The driver was also in the front of the hull, but seated to the extreme left side, to make space for the secondary turret, where the secondary gunner and loader worked. Also in the front of the hull, underneath the secondary turret. was a flamethrower of unspecified type. The position of the radio operator is, once again, unclear.
Armor
The hull consisted of 130 mm of frontal armor plates, while the sides and rear were 125 mm thick. The belly and roof were 50 mm thick. The front of the turret consisted of a 130 mm plate angled at 60° from horizontal, for a relative thickness of 150 mm. The sides and rear of the turret were also 125 mm thick.
Armament
Like on most other KV-4 designs, the main gun was the 107 mm ZiS-6 (F-42) developed by V.G. Grabin at Plant No.92 from autumn 1940 to spring 1941, and was later tested on a KV-2 in June 1941. It was a potent anti-tank cannon, with a muzzle velocity of 800 to 840 m/s and a shell weight of 18.8 kg, with a calculated penetration of 115 mm of armor at 1,000 meters. The main gun had +20° elevation and -5° depression (same applies for the 45 mm coaxial). The 45 mm in the secondary turret variant had +25° elevation and -5° depression.
The 45 mm 20-K mod.1937 was still widely used on Soviet tanks at the time, but by 1941, its anti-tank capabilities were lackluster. However, it still provided good performance against soft-skin targets.
For defense against infantry, a 7.62 mm DT machine gun was placed in a ball mount in the rear of the turret, but the two-turret variant had an additional coaxial DT machine gun. The two-turret variant also featured an unspecified type of flamethrower in the front of the hull, to be operated by the driver or secondary gunner.
Discontinuation of the project
After the announcement of the competition results, the KV-4 project stagnated, with SKB-2 focusing on the KV-3 and KV-5. Progress on these heavy tank projects was further halted by the start of the war on 22 June, as the LKZ factory shifted focus to the production and repair of KV-1 tanks.
The situation would turn grave when German forces were approaching the city of Leningrad, home of the LKZ plant. In September, the SKB-2 design bureau was moved to ChTZ to continue work. However, with this move, the KV-4 and KV-5 projects were not reconsidered and canceled. Only the KV-3 project remained active, but with focus on improving the KV-1 tank, no progress was made on the KV-3 either and it was canceled by 1942.
Conclusion
The rational and conventional KV-4 design presented by A.S. Ermolaev offered a realistic alternative to the more unorthodox designs, landing him the fourth spot in the competition. Still, the high crew number and excessive weight, especially for the two-turret variant, could have proven problematic. The entire project was deemed expensive and irrelevant to the military needs of the Soviet military, even by its own designers. Once abandoned following the SKB-2’s move to ChTZ, the project was forgotten.
KV-4 Ermolaev variant with 2 turrets. Illustration by Pavel Alexe.
KV-4 Ermolaev variant with a single turret. Illustration by Pavel Alexe.
KV-4 Ermolaev Specifications
Variant
1 Turret
2 Turrets
Dimensions (L-W-H)
8.22 x 4 x 3.25 m
8.52 x 4.00 x 3.25 m
Total weight, battle-ready
90 tonnes
95 tonnes
Crew
6 men (commander, gunner, 2x loaders, driver, radio operator)
8 men (commander, main gunner, 2x main gun loaders, driver, secondary gunner, secondary loader, radio operator)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40-45 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K (?)
7.62 DT machine gun
107 mm ZiS-6 (F-42)
45 mm 20-K
2x 7.62 DT machine gun
Flamethrower
Armor
Turret: 125-130 mm
Hull: 125-130 mm
Top: 50 mm
Belly: 50 mm
Even before the KV-1 entered mass production, there were plans to improve its characteristics, most importantly the armament and armor. One of these was the KV-220, an attempt to improve the armor of the KV-1 up to 100 mm, and increase firepower with an 85 mm F-30 gun. Designed and built at the Kirov Leningrad Plant, two prototypes were finished in late 1940 and mid-1941 after a convoluted history. They then saw combat in the Leningrad area with the start of the Great Patriotic War (Operation Barbarossa).
The KV-220 before its trials, January 1941.
Source: Tank Archives, colorized by Johannes Dorn
The KV-1
The experiences gathered during the Winter War (November 1939 – March 1940) against Finland gave the Soviets invaluable tactical and technical information regarding development and use of heavy tanks. The massive SMK (from LKZ, Leningrad Kirov Factory) and T-100 (from Plant No.185) multi-turreted tanks were attempts to create a successful breakthrough heavy tank. Nevertheless, their fundamentally troubled design, based on the hopelessly obsolete T-35, would fail them. The U-0, essentially a smaller, lighter, one-turreted SMK, would prove to be far more successful during its trial combat period on the Karelian Isthmus. Consequently, on 19 December 1939, 50 such tanks were ordered. The tanks would be known with the acronym KV, from Kliment Voroshilov, the People’s Commissar of Defense of the Soviet Union at the time, but as they were preseries production, each vehicle was documented with U-XX, with each new tank receiving a new, higher number.
The U-0, armed with a 76 mm L-11 gun and a coaxial 45 mm 20-K gun. It would see combat on the Karelian Isthmus from December 1939.
Source: Topwar
Despite the KV’s improvement over its larger predecessors, it was still far from perfect. By July, only 32 tanks had been built (including 14 KV-2s, or, as known at the time, ‘Big Turret KVs’). This was caused by the fact that the KV’s were not fully refined yet, with countless mechanical and production flaws. Each new U-series tank was unique, with different features meant to fix previous problems. This was accounted for from the beginning, as mass production was expected to begin by 1941. However, Stalin’s patience waned. In what would become “The Stalin Task” via a decree from the Council of People’s Commissars of the Soviet Union, it was required that LKZ reach a yearly production quota of 230 KV tanks of both turret variants (130 small turret and 100 big turret), essentially forcing the still unrefined tanks into service. This move would have detrimental effects on the KV-1 and KV-2 throughout their service life.
Only by August 1940 could full scale production of the KV tanks begin, with 20 built in August and 32 units in September, surpassing the expected monthly quota of 20 vehicles.
Stacking Weight
As early as May 1940, the GABTU (Main Directorate of Armored Forces) and the People’s Commissariat of Heavy Engineering considered improving the armor of the KV-1. This was a curious move, as the KV-1, with 75 mm of armor all-around, was capable of withstanding fire from most anti-tank guns used at the time. Perhaps even more bizarrely, would be that the KV-1 was struggling to function at its 44 tonnes. The wiggling room for additional armor was small.
First concrete mentions of thickening the armor of the KV came on 11 June, suggesting to up-armor the tank to 90 to 100 mm. Around a month later, on 17 July, the Council of People’s Commissars of the Soviet Union adopted decree No. 1288-495§, which stated:
By November 1, 1940, the Kirov Plant will produce two KV tanks with 90 mm of armor: one with a 76 mm F-32 gun, the other with an 85 mm gun. The Izhora Plant will deliver one hull at the end of October, the production of the tank is scheduled to be completed by November 5. The second hull will be made by November 5th.
By December 1, 1940, the Kirov Plant will produce two KV tanks with 100 m of armor: one with a 76 mm F-32 gun, the other with a 85 mm gun. One hull will be delivered by the end of October and by the end in November.
The first paragraph discusses two tanks, both integrating 90 mm of armor all-around. The variant armed with the 76 mm F-32 gun would become the T-150, while the one with the 85 mm F-30 would become the T-221.
The second paragraph mentions another two tanks, with 100 mm of armor all-around. Like previously, one was to be armed with the 76 mm F-32 and the other with the 85 mm F-30. The latter would become the T-220. What exactly happened to the variant with the 76 mm gun is unclear. It was likely either dropped in favor of the T-150 or incorporated within the T-220.
Despite the decree, work did not begin immediately. LKZ was working full-time on improving the existing KV-1 and KV-2, and preparing for their mass production. Further delays were caused by the GABTU sending the specific technical requirements late.
The new tanks were to be designed at LKZ’s SKB-2 design bureau and the prototypes would be built at the Izhora plant. The projects were handled by the head of SKB-2, J.Y. Kotin, who, in August 1940, would appoint several teams for the development of the tanks. For the T-150, Kotin appointed Military Engineer L.N. Pereverzev as head of the project, while the T-220 team was to be headed by L.E. Sychev. An experienced tank engineer, Sychev had worked on the T-28, SMK, and KV-1, having completed his bachelors at SKB-2 in 1932 and after graduating in 1934, starting work at SKB-2. At some point during the project, Sychev was replaced by B.P. Pavlov as head designer. Gun installation and mechanism were designed by P.F. Muraviev, while the transmission was designed by N.F. Shashmurin. Ultimately, the design team of the T-150 (and likely KV-220 as well) consisted of B.P. Pavlov, L.E. Sychev, V.K. Sinezersky, S.V. Kasavin, F.A. Marishkin, and N.F. Shashmurin.
Joseph Yakvolevich Kotin, at the time head of the SKB-2 design bureau of LKZ. He would be the man behind most Soviet heavy tanks.
Source: Andrei BT Leonid Efimov Sychev, chief designer of the KV-220. He was born in 1913 and was native to Leningrad (St. Petersburg).
Source: Museum of SPbPU
When designing the T-220, Sychev’s team encountered several issues. It was clear that the hull of the KV-1 was not big enough to accommodate the larger turret or additional 25 mm of armor. Additionally, the tank would have been significantly heavier, and a much more powerful engine was required. The clear choice was to lengthen the hull by 1 roadwheel, allowing for a much larger 850 hp V-2SN engine, as well as comfortably fitting a longer turret. Ground pressure was also lowered. The tank was named T-220 and later called Object 220 and KV-220.
Fitting the 85 mm F-30 gun in the KV-1 turret was ruled out, as it was simply too large. Instead, a turret inspired from the earlier designed KV-2 was drawn. It featured long side walls, allowing the crew members to adequately operate the gun, as well as a smaller turret on top armed with a DT 7.62 mm machine gun.
By September, the technical documents and drawings were ready and were sent to the Izhora plant for prototype production. However, the Izhora plant Hall No.2 was working at full capacity with the production of KV-1 and KV-2 tanks, with four tanks on the lines at the same time. Consequently, the construction of the prototype was delayed, and the tank was sent to the factory, complete, on 7 December, six days late. This first tank was given serial number M-220-1.
The finished KV-220 tank without machine guns at LKZ. Note the KV-2 turret in the bottom left corner.
Source: TsAMOThe lighter “brother” of the KV-220, the T-150 (KV-150/Object 150). Colorization by Johannes Dorn
Source: Warspot
Second Prototype
A second KV-220 was to be built as well, with the serial number M-220-2. The exact characteristics of this prototype had been tinkered with several times, which led to a very delayed production, with various sources claiming that this was in fact the Object 221, while other data contradict this claim. It is possible that this prototype was to be the 76 mm F-32 armed KV-220, but at the start of February, the turret of the tank was at Plant No.75, awaiting installment of the same 85 mm F-30 gun as on the M-220-1. On 19 February, the tank was instead to be armed with the 107 mm ZiS-6 after a series of studies had been made. Construction of the second prototype would only begin by 7 June and the military representative of LKZ, Military Engineer 2nd Rank A. Shpitanov, would claim that the tank would be ready no earlier than 10-15 July.
Object 221/T-221
Between the T-150 and T-220, there was a third vehicle, as originally requested in July 1940. It was to have 90 mm of armor, as the T-150, but with the same 85 mm F-30 gun as on the KV-220. The result was essentially just a KV-220, but with just 90 mm of armor, as opposed to 100 mm, and named T-221 (Object 221). Thus, due to its appearance, this vehicle is often confused with the KV-220. On 19 February, its armament was changed to the 76 mm ZiS-5 gun, and the turret was to be produced by 1 March. Only a mock-up was built in March 1941, and its mock-up chassis was later used on the mock-up of the Object 223 (KV-3).
Object 212 SPG
Another project based on the KV-220 was the Object 212 SPG, also named in documents as just 212, but not to be confused with the KV-based tractor with the same index. It was meant as a genuine bunker buster vehicle, intended to replace the KV-2, as a result of the sour taste left by Finnish fortifications encountered during the Winter War. It was to be armed with the 152 mm Br-2, based on the inverted chassis of the KV-220, with a large casemate. Only some components were built until the evacuation of SKB-2 in August 1941, and the entire project was transferred to UZTM factory, where development would continue slowly until the project died out, largely due to the cancellation of the KV-220 and later the KV-3.
The Object 212 SPG. Note the KV-220 inverted chassis
Source: Warspot
Design
The addition of 25 mm of armor all around and the larger 85 mm gun necessitated a major overhaul of both the hull and turret of the KV-1. The thickening of the armor was done outwards, which allowed for very similar interior dimensions to those on the KV-1.
Firstly, the hull was elongated to over 7.8 m, most noticeable with the addition of an extra roadwheel and return roller. The lengthened hull allowed for the mounting of a larger engine, as well as decreasing the ground pressure of the tank. As the tank was to be far heavier, a new engine was required, and the 850 hp V-2SM experimental engine from Plant No.75 was chosen.
Secondly, and most importantly, the turret was a completely new design. It was largely based on the turrets of the KV-2 and Object 222. A large curved mantlet with gun housing was mounted on the flat frontal turret face. The sides were vertically flat, but had a slight curve along their length. The rear was also flat, but featured a large square door, used for entry and exit of the crew, ammunition replenishment, and removing the armament. The sides of the turret were flat, as opposed to angled at 15°, as both Kotin and factory director I.M. Zaltsman noted that mounting the turret walls at a right angle allowed for far stronger joints and easier production, without sacrificing much in terms of protection.
Across the upper edge of the turret, five handles were added for easier climbing on the large turret for the crew. On each side, a firing port for crew weapons was added.
Side view of the KV-220.
Source: Tank Archives
Perhaps one of the most interesting features of the KV-220 was the small secondary turret, which also acted as a commander’s cupola, with full 360º traverse. It was very similar to those designed by Plant No.185 for their T-103, though there might be an element of coincidence. It had four periscopes, one facing each direction. A 7.62 mm DT machine gun was mounted within. The cupola armor was also 100 mm thick all around, making it cramped when loading and firing the machine gun. The cupola was just large enough for the commander to fit his head. No service hatches were given. Another problem with the cupola was the firing blindspots created by the periscopes in front of it, especially the rotating PTC periscopes.
Rear view of the KV-220. The joint reinforcing rods can be seen on each side of the turret rear.
Source: Warspot
Crew
The larger turret and gun now required an additional loader, bringing the total crew to 6: tank commander, gunner, two loaders, bow machine gunner/radio operator, and driver-mechanic. The latter two were seated in the hull front, much like on the standard KV, with the driver in the center and radio operator to his left. Behind the driver was an emergency exit hatch in the floor.
The other four crew members were cramped in the turret, with the gunner to the left of the main gun. The commander was placed behind him and could control the machine gun turret. The two loaders were to the right of the gun.
Armor
The hull armor was nearly identical in layout and angling to the one on the KV-1, just 25 mm thicker, reaching 100 mm. The front had an angled lower plate, 100 mm, thick meeting with the belly (30 mm) and upper frontal plate (90 mm at 20º from horizontal) meeting into the frontal shield (100 mm at 60º). The sides were completely flat, also 100 mm thick. The rear, just like on the KV-1, consisted of two plates, the lower being 100 mm and the upper portion just 50 mm, as the engine cooling system was behind it.
The turret had 100 mm of armor all around, and the joints were welded together and reinforced by rods, which would run across from one plate into the other. It is important to acknowledge that the KV-220 was one of the first tanks where the Soviet industry had to deal with such thick armor.
Internal cutout view of the Object 220, showing the internal layout and details of the new turret. The blueprint is dated 6 January 1941.
Source: Edit from Stalin’s Supertanks IS-7
Propulsion
The engine used was the V-2SN 850 hp diesel engine developed by Plant No.75, which was a boosted variant of the V-5 engine (with a supercharger from the AM-38 aircraft motor combined with a pressurization system), which itself was a boosted variant of the V-2K engine used on the KV-1. Naturally, the engine was bound to become problematic due to its unstable nature. The tank was able to carry 825-845 liters of fuel.
Unlike its smaller ‘brother’, the T-150, the unreliable KV-1 gearbox was not used on the KV-220, but rather a reinforced and slightly modified version designed by N.F. Shashmurin. These alterations included a more compact box, improved tolerances and better dynamics. This was a crucial step in the right direction, not just for the KV-220 but for future KV tanks, which were to be fitted with better gearboxes.
Internal cutout top view, showing the engine, gearbox, and other hull components.
Source: Edit from Stalin’s Supertanks IS-7 KV-220 gearbox designed by N.F. Shashmurin.
Source: V. Lehn
Armament
The main armament on the KV-220 was the 85 mm F-30, developed at Factory No.92 by V.G. Grabin. It was based on the F-27 75 mm gun, but chambered for the larger 85 mm round and with improved recoil systems. The gun was installed and tested on the T-28 in spring 1939, and after a series of firing trials, was deemed satisfactory. Ballistically, the gun was near identical to the 52-K anti-aircraft gun, and shared ammunition.
T-28 medium tank armed with the 85 mm F-30, used for the gun’s testing.
Source: Yuri Pasholok
Mounting of the gun on the KV-220 was conceived by P.F. Muraviev. A PT-6 sight would be used for aiming, and a PTK panoramic periscope for battlefield vision for the gunner. The tank carried 91 rounds for the 85 mm gun, with at least 15 rounds stored in the turret bustle. The rest were in the hull, stowed in two different frames.
Secondary armament consisted of three DT 7.62 machine guns, one in a ball mount in the hull bow, one coaxially (right) with the main gun and one in the cupola. For these, 64 drums were provided, for a total of 4,032 rounds.
85 mm F-30 gun specifications
Muzzle velocity (m/s)
793
Shell weight (kg)
9.2
Penetration
88 mm from 1 km @ 30º
Trials
After the KV-220’s (M-220-1) reception in early December, the tank was inspected and prepared for trials. On 14 January 1941, an order from the People’s Commissariat of Defence and People’s Commissariats of Heavy Engineering requested that the T-150 and KV-220 tanks undertake driving and chassis trials at LKZ.
A commission, headed by assistant head of testing, Military Engineer 1st Rank Glukhov, and consisting of GABTU and LKZ officials, were to analyze the tanks and establish the following goals:
Determining the tactical and technical characteristics of the tank
Identifying the shortcomings in the designs and their elimination prior to mass production
Judging whether it is possible to conduct military tests
Accumulating data for operating and repairing the tanks
T-150 towing the KV-220 after it broke down. Although it also suffered a critical engine failure, the T-150 would get much further with its trials.
Source: TiV 11 2014
From a letter dated 28 January 1941 from Glukhov, reporting on the progress of the trials, several alarming details can be found, as both tanks broke down during driving trials. For the KV-220, it broke down while driving around the factory, on 21 January, as the engine failed after its main bearings melted. A new engine would be fitted a week later.
Another issue found with both the T-150 and KV-220 was when they were weighed. Both had surpassed the initial weight threshold imposed. The KV-220 weighed 62.7 tonnes, instead of 56 tonnes.
A second report from Glukhov would reveal the true failure of the KV-220’s engine. The tank had traveled 106 km and the engine worked for 5 hours and 51 minutes, allowing the 62.7 tonne tank to reach a top road speed of 21.2 km/h (according to Yuri Pasholok, 33 km/h) and averaged 18.6 km/h. During operation, hot engine oil was squirted from the engine cooling vents on top, as well as encountering power loss due to piston ring wear. Thus, oil usage spiked uncontrollably, to 15.5 liters per hour of operation, or 0.83 liters per km.
The KV-220 driving through heavy mud.
Source: Warspot
Unlike the T-150, the KV-220 never undertook firing trials either, mostly because of the unbalanced gun and the foot trigger being poorly made, an issue discovered in December 1940, and which would be postponed. On 19 February 1941, after a letter specifying the issue from Deputy People’s Commissar of Armament Mirzakhanov, Marshall Kulik would request that the KV-220’s turret be sent to Plant No.92 for alterations of the gun mechanism, but a specific date or deadline was not given.
The failure of the engines was not a surprise. In fact, before the trials, Plant No.75, through T.P. Chupakhin, could not guarantee the operation of either the V-5 engine on the T-150 or V-2SN on the KV-220. On 28 January 1941, another V-2SN engine was brought in and trials continued, but this one failed a few days later, on 3 February. Another engine could not be provided until 15 February.
In order to fix these crucial problems, a commission was set up on fixing and refining the V-5 and V-2SN engines, consisting of Glukhov, Chuptakhin, head of tank production at LKZ A.I. Lantsberg, as well as representatives from GABTU. The commission would determine that the engine trials were done prematurely and that they required operation testing, not field trials on tanks. Plant No.75 was tasked with finishing testing and fine tuning the engines by 10 April, and by the same date, the engines and improved cooling systems were mounted and tested on said tanks.
When the news of the failed trials of both tanks reached the GABTU and People’s Commissariat of Heavy Engineering, the head of the armored department of the GABTU, Military Engineer 1st Rank Korobkov, sent a letter to LKZ director I.M. Zaltsman demanding the engines to be fixed and continuing trials.
The KV-220 and the T-150 were covered with tarpaulins during trials to protect the gun, sights, and other sensitive equipment from the elements.
Source: Tank Archives KV-220 driving on a slope during trials.
Source: TiV No.11 2014 Removing the KV-220’s engine’s plate, likely after the engine broke down during trials.
Source: Warspot Removal of the transmission after critical powerplant failure on the KV-220. Note the T-150 to the right.
Source: TiV 11 2014
The KV-220 was not a cheap tank project. A report dated 30 May 1941 mentions in detail the developmental costs of KV experimental tanks, which in total amounted to 5.35 million rubles. The KV-220 alone cost 4 million rubles, this sum including both the KV-220-1 and KV-220-2. For context, a KV-1 Mod.1941 would cost between 523,000 to 635,000 rubles.
Stage of KV-220 Development
Price (thousands of rubles)
Draft drawings
100
Scale models
25
Technical drawings
250
Prototype construction and factory trials
1200+1200
Proving ground trials
125+125
Drawing correction after trials
75
Repair of prototypes and improvements
450+450
Total cost
4,000
Source: CAMD RF 38-11355-101
Fitting the 107 mm F-42 (ZiS-6)
Both Kotin and Grabin had juggled with the idea of installing an 107 mm gun in a tank since 11 June 1940, originally in the KV-2. By August 1940, SKB-2 engineer G.N. Moskvin was tasked with researching the fitting of a 107 mm gun inside the KV-220 turret. The gun would turn out to be the 107 mm F-42, developed by December of the same year, and which was later indexed ZiS-6.
Initial calculations revealed that fitting the F-42 gun in the KV-220 turret would have raised great challenges, especially regarding the movement of the shells within the tank, as they were simply too long. Factor in bouncing of the tank while driving, and the loader’s job was impossible. The round was 1,200 mm long and weighed 18.8 kg. Splitting it into two, like on larger 122 mm and 152 mm rounds, was impossible.
Chief designer of Plant No.92, V.G. Grabin, on a trip at LKZ, would try to convince Kotin and the tank engineers that it was possible to fit the F-42 inside the KV-220. After struggling to fit inside the turret hatch, he was unable to lift the shell from the hull floor and into the turret. He would then criticize the tank designers for their reluctance to change the design and stated that the tank was merely a gun platform.
The second KV-220 prototype, M-220-2, was to be originally armed with the 76 mm F-32, and later the 85 mm F-30, as on the first prototype. However, by 19 February, the F-42 would appear again in a letter from Marshal Kulik, stating that the second prototype of the KV-220 was to be armed with the 107 mm F-42 gun at Plant No.92, where the turret was already at. Although the KV-220 was never fitted with the gun, its immediate offspring was.
Overlay of the 107 mm ZiS-6 (F-42) on the KV-220. Also note the difference in size between the 107 mm and 85 mm shell.
Heavier Tanks
By March, the improved engines from Plant No.75 were ready to be tested, but the situation was starting to change. On 1 March, the T-150 had been replaced by the Object 222, which featured a new, improved turret on the same hull. Shortly after, on 11 March, a letter from the intelligence services to the GABTU regarding German tank developments would lead to a series of changes in tank developments.
The highlight of the report was a 90-tonne Pz.Kpfw.VIII armed with a 105 mm gun, which would become the Löwe in late 1941. As a response, on 17 March, the GABTU tasked LKZ with designing an equivalent tank, namely the Object 224 or KV-4, weighing 72 tonnes and armed with the 107 mm ZiS-6, a secondary 45 mm gun, various machine guns, and a flamethrower. Frontal armor was to be 130 mm and side armor 120 mm.
By 7 April, the GABTU had reconfigured their requests. The Object 223 was born, which was a direct evolution from the KV-220 with thicker armor, up to 120 mm on the hull, and an entirely new turret made out of stamped armor sheets, also fitted with the ZiS-6. The turret was far larger than that of the KV-220, made out of 120 mm armor. The KV-4 was also altered, with a weight of at least 75 tonnes and side armor thickness increased to 125 mm. Lastly, a 100-tonne tank was requested as well, Object 225 or KV-5, with 170 mm of frontal armor, 150 mm of side armor, and the same 107 mm gun.
Combination of several photos of the Object 223 (KV-3). The hull of the mock-up was actually borrowed from the T-221 (Object 221), which was essentially just a KV-220 with 90 mm of armor.
Source: Yuri Pasholok
As a result of these developments, the KV-220 became sidelined, but its mere physical existence made it crucial in the development of the Object 223 (KV-3). For trial purposes, the hull of the KV-220 would be used, but with a V-5 engine which was to be replaced with a V-2SN once they were available. Between 12 and 14 April, weight tests with 70 tonnes were done on the chassis, to simulate the weight of the KV-3, with several issues discovered:
Leak from the V-5 engine’s crankcase
Incredibly slow speed and low power, the tank only being able to drive in 1st and 2nd gear off-road
2 idlers had to be replaced
2 roadwheels were damaged
1 torsion bar was damaged
With this smaller engine, the trial tank sustained a consumption of 2.9-3.2 liters per kilometer (31-34 liters per 100 km).
The Object 224 (KV-4), namely the winning design of the KV-4, by N.L. Dukhov would be an enlarged KV-220. The hull was much larger and the turret was equipped with a loading assistant mechanism for the large shells. There are at least two documents mentioning the KV-220 as the KV-4, before the Object 224 existed, which makes sense considering the T-150 was also temporarily called KV-3.
KV-4 design by N.L. Dukhov, essentially just an enlarged KV-220.
Source: ASKM
During May and June 1941, SKB-2 was busy working on the technical details of the Object 223, 224, and 225, as well as conducting firing trials of the ZiS-6 gun mounted on a KV-2. But with the Axis’ invasion of the Soviet Union, priorities changed. The heavy tank losses suffered by the Soviets required massive efforts from both repair units, but also factories to ramp up tank production and repair. Thus, progress on the massive heavy tanks slowed down. Likewise, the KV-1 proved to be catastrophically unreliable, although its excellent armor shined several times, and work had to be done to improve the tank.
It is worthy to mention that during the same period, the KV-2 was armed with the 107 mm ZiS-6 fitted via a KV-3 mantlet and firing trials were held.
KV-2 during firing trials, middle of June 1941. The man with white uniform was V.G. Grabin himself. The KV-220 was also meant to be armed with this gun, but it was simply too large.
Source:Bronetechnika.narod.ru
Second Trials
Despite the development of the new heavy tanks, work on the KV-220 continued. On 31 May, a third V-2SN engine was delivered by Plant No.75. The new engine (serial number 1193-03) worked well, and by 20 June, the tank had rolled a total of 1,979 km, of which 583 km between May and June. The engine worked for 27 hours and 21 minutes. There were still several problems with the tank:
10 of the 14 roadwheels sustained rim damage and one was cracked.
5 return rollers suffered damage to the rubber.
Right final drive failed due to failure of 2 ball bearings, 2 roller bearings, 1 cone bearing, and the main gear was worn out and had heat damage
In response, changes were made to the tank, such as thickening the amount of rubber on the return rollers, of which half had rubber compressed at 16 tonnes and the other half at 18 tonnes. Other changes were the replacement of old filters with the experimental ‘Vortex’ oil filters , which had a mushroom shaped filter for trapping oil, as well as new exhaust manifolds and compensators.
Combat
For LKZ, the situation turned sour in August, when the German forces were knocking on the doors of Leningrad. Many SKB-2 engineers were evacuated to the ChTZ plant in Chelyabinsk, alongside some tank prototypes for further work, like the KV-3 (Object 223), which was meant to continue development. The KV-4 and KV-5 were discontinued. Interestingly, based on an order from Zaltsman on 30 June, the KV-3 was to be shipped to ChTZ with the V-2SN engine from the Object 220. This likely never happened.
The T-150 and the two KV-220 prototypes suffered a different fate. Kliment Voroshilov, member of the State Defense Committee, had a meeting with LKZ officials, including I.M. Zaltsman in Smolny, requiring prototype vehicles to be made combat ready in order to defend Leningrad. According to Military Engineer A.F. Shpitanov, 20 tanks were prepared for combat. They were placed in the Kirov district in Leningrad.
But how exactly the KV-220 tanks were to be used in combat was unclear. The M-220-1 prototype was functional, but the 85 mm F-30 was never tested and the gun was unbalanced, thus unsuitable for firing. The M-220-2 prototype had just left the production line in mid-July, but it still had no turret. The logical solution was that each of the tanks were fitted with standard KV-1 turrets, armed with the 76 mm F-32 guns.
The two KV-220 prototypes were sent to the 124th Brigade, with prototypes M-220-1 and M-220-2 being sent on 5 and 16 October respectively to defend Leningrad district. Not much is known about the fate of the first prototype, but the second one has a much more interesting story.
Documents show that the 124th Brigade, including tank M-220-2, named ‘For the Motherland!’, and likely prototype M-220-1 as well, were engaged in combat in the Ust-Tosno area, south-east of Leningrad, alongside 43rd Rifle Division.
On 11 November, at 12:00, the 124th Brigade and 147th Infantry Regiment assaulted a railway bridge in the direction of Ust-Tosno. Fighting commenced around the railway embankment and the bridge over the Tosna River. In total, 19 KV tanks were lost, of which 5 were burned. The KV-220 (serial number M-220-2) was likely one of these.
Russian historian Maxim Kolomiets interviewed with D. Osadchim, who was commander of a KV tank company belonging to the 124th Brigade in autumn 1941. Regarding the KV-220 he recalled:
“In the autumn of 1941, our brigade received several KV tanks for replenishment, one of which was called “For the Motherland!”. It was made in a single copy at the Kirov plant. It had the same capabilities as the KV tank, but had enhanced armor protection, a weight of more than 100 tonnes and a more powerful turbine engine. When driving in higher gears, the engine whistled, and this whistle was very similar to the whistle of the Junkers dive bombers. The first time after receiving the tank, when driving, the brigade even gave the signal “Air!” (raid). The tank entered my company, and at first they wanted to appoint me as its commander, but then my deputy, an experienced tanker, Lieutenant Yakhonin, became its commander. The tank was considered almost invulnerable to enemy artillery and was intended for assaulting fortified positions.
In December 1941 (I do not remember the exact date) our brigade was given the task of breaking through the German defenses in the Ust-Tosno section – the railway bridge, crossing the Tosna River and, in cooperation with units of the 43rd Rifle Division, developing an offensive on the Moscow State River. In the first echelon, I attacked as part of the 2nd Tank Battalion under the command of Major Paikin, while in the 1st Battalion was the tank “For the Motherland” from my company. In this battle, the tank was given the task of capturing the railway bridge over the Tosna River and holding the bridgehead for the approach of the main forces. The battle unfolded in an open area. The frozen top layer of peat bog could not hold the tank. When it came close to the bridge, it was met with fire from German heavy guns, and radio contact with them was lost. I was at the battalion’s command point at the time. When communication with the tank “For the Motherland” was interrupted, I tried to make my way to the scene along the railway embankment. When I managed to crawl up to the tank, I saw that the turret had been knocked down and the entire crew had been killed.”
It is important to highlight that Osdachim’s report was not entirely accurate, though it is understandable, as the interview took place at least 40 years after the fact. Nonetheless, it provides a good picture of how its users saw the machine, as well as the events of how it was lost.
In a tank write-off report from the 55th Army, the tank M-220-2 from 124th Brigade was listed as irreversibly lost via burning and it mentions that the tank had not been recovered. Its crew, tank commander Jr. Lieutenant Yakhnin, driver-mechanic Kypuladze, gunner Efremov, radio operator Matinov, loader Antipov, and radio operator Afanasyev, all succumbed to the fire. After the engagements, 17 KV tanks were recovered.
On 18 March 1942, a KV-220 tank was listed in the inventory of the 84th Heavy Tank Battalion, part of the 55th Army. The tank was also named ‘For the Motherland!’ and was commanded by Lt. Smirnov and crewed by Pugay, Prokhorov, Boykov, and Vikhorov.
In late 1942, one KV-220 was repaired at Plant No.372. A propaganda video titled Leningrad’s Struggle from 1942, shows a KV-220 with a KV-1 turret and painted white being lifted off the repair line of Plant No.372. Here, the tank was fitted with a standard V-2K engine. It is unknown which of the two tanks it was.
Frame captured from the propaganda video Leningrad’s Struggle, showing one of the KV-220s armed with a KV-1 turret, sometime during 1942.
Source: Leningrad’s Struggle
Normally, burning of the tank would mean scrapping, but the KV-220 with serial number M-220-2 would reappear once again in a report on 8 February 1943 in the tank inventory of the 12th Tank Training Regiment. The tank, still with the slogan ‘For the Motherland!’ was appointed to tank commander V.V. Strukov. The tank would be used for training until 1944.
The other KV-220, M-220-1, likely had a much shorter fate. In autumn/winter 1941, the tank was sent to defend the northern Kirov district, western Leningrad, with driver-mechanic V.I. Ignatiev. The vehicle was assigned to defend Petergofske Boulevard at the bridge over the Krasnenkaya River (a portion of which today is called Stachek Avenue), about 1 km from LKZ. The tank was likely lost here.
In 1949, before the 10th Anniversary of the start of defense of Leningrad, Kotin proposed the creation of a monument in the exact spot where the KV-220 was lost. The monument was unveiled in 1951 and still stands to this day, and displays a KV-85 tank (actually a hybrid between the KV-122 prototype hull and IS-1 prototype turret) in Leningradsky Square.
Monument with the KV-85, allegedly raised in the same spot where the KV-220 was lost, coordinates: 59°51′40″N 30°15′30″E
Source: Alex Fedorov
It was not just the hulls of the KV-220 that saw combat, but also the turret of the first prototype. After it was dismounted from the tank, it was sent to Karelia, where it was integrated into a static firing bunker (BOT) in the 22nd Karelian Fortified Area. It was indexed BOT KV with 85 mm ‘Victory’ gun. It would not see action. This would not be the only turret to suffer this fate, the T-100Z prototype turret was also moved into a Karelian firing point.
The turret of the KV-220 with the F-30 85 mm gun, Karelia.
Source: Warspot
Legacy
The KV-220, much like its heavier brethren, can be today seen as a large waste of resources, at a time when the Soviets officials and LKZ were rushing the unfinished and unreliable KV-1 into service. The heavier tanks, like the KV-220 and KV-3, although having excellent characteristics on paper, would prove to be expensive, complicated, and their origination from the KV-1’s mechanical components, although improved, would have likely affected the even heavier tanks.
Regarding the KV-220, the Soviets had essentially designed, built, and tested a heavy tank on similar capability levels as the infamous German Tiger I tank. While this comparison might seem of historical irrelevance, it was made by Kotin himself after seeing the Tiger tank for the first time.
The first Tiger I tank was captured by the Soviets on 16 January 1943, the tank having been disabled by artillery fire, and a second almost intact Tiger, with technical documents, tools, and ammunition, was captured on 17 January. A rifle platoon and 4 Soviet tanks were sent in for recovery. Both tanks were sent to the Kubinka proving grounds, where both J.Y. Kotin and head of Plant No.100, A.S. Ermolaev, who also worked at SKB-2 before the war, were able to analyze the tank. It is here where they would learn that the Germans were just now fielding a tank on par to the KV-220, designed over 2 years prior. After the analysis, Kotin would write:
“The tank was impressive, it had an 88 mm cannon and two machine guns. Frontal parts of the hull and turret are protected by strong armor. Despite this data, we saw the tank’s “Achilles heel” so to speak– a vulnerability. Previously, Hitler’s machines were lighter, more maneuverable, developed greater speed – in a word, they were created for the offensive. “Tiger” weighed almost 55 tons, moved slowly, was clumsy, was more suitable for defensive combat. By the way, it was because of its poor maneuverability that it fell into our captivity.”
One can argue Kotin was describing his earlier heavy tank creations, though it is true that the Soviets were not fighting an offensive war.
Conclusion
The KV-220 was a powerful heavy tank based on the KV-1 and was well ahead of its time in terms of technical capabilities. However, much like its predecessor, the KV-1, it was plagued by mechanical problems, primarily in the form of the experimental V-2SN engines. Once the powerplant had been sorted, it proved to be a capable platform, which unfortunately never got to test its equally capable 85 mm F-30 gun. While it did serve as a platform for the even more powerful KV-3 and KV-4 tanks, the entire philosophy of adding extra armor and large armaments on the platform of the KV-1 was faulty. The two KV-220 prototypes would see action on the outskirts of Leningrad, but were lost in combat.
KV-220. Illustration by Pavel Alexe.KV-220 with 107mm ZiS-6 gun. Illustration by Pavel Alexe.KV-220 with a regular KV-1 turret. Illustration by Pavel Alexe.
KV-220 (Object 220/T-220) Specifications
Dimensions (L-W-H)
7.83 x 3.41 x 3.11 m
Total weight, battle-ready
62.7 tonnes
Crew
6 (Commander, gunner, driver, radio operator/bow gunner, 2x loaders)
Propulsion
V-2SN 12-cylinder diesel, outputting 850 hp w/ AM-38 supercharger
Speed
33 km/h
Suspension
Torsion bar, 7
Armament
85 mm F-30 (91 rounds) later replaced w/ 76 mm F-32
3x 7.62 mm DT machine guns (4,056 rounds)
Armor
Front/sides/rear of hull and turret: 100 mm
Top/Belly: 30 to 40 mm
Object 212 SPG illustrated by Pavel 'Carpaticus' Alexe
Soviet Union (1940-1941)
Heavy Self-Propelled Gun – Only Components Built
Even after the KV-2 entered service with the Soviet military, its mediocre concrete penetration still left the Soviet artillery units craving for a more powerful bunker buster after the encounters with the Finnish Mannerheim Line. Development would lead to the Object 212 SPG, but due to the start of the war with Germany and no immediate need for such a vehicle, progress would slow down until it was canceled completely.
Cracking the Mannerheim Line
The Winter War (November 1939 – March 1940) between the Soviets and Finnish taught both sides a series of lessons on fighting a modern war. For the Soviets, this meant incorporation of armor and penetrating the heavily fortified lines of the Mannerheim defensive line on the Karelian Isthmus. Its construction began in the early 1920s, but those segments were poorly built and out of cheaper materials, such as wood. A second plan of building the line started in 1932, which included concrete bunkers with underground sections. Fixed gun mounts of various calibers, trenches, and traps, such as anti-tank pyramids and barbed wire, were meant to funnel attacking troops towards well dug-in defenders. These defensive features combined with the marshy area, with either bogs, lakes or thick forest in winter time, posed a difficult fighting area for the attacking Soviet troops. The line managed to delay the Soviets for a few months.
The three layers of the Mannerheim Line on the Karelian Isthmus, the main line in dark blue, intermediate line in lighter blue and final line in very light blue, towards the north.
Source: S. Korhonen via Winterwar.com
The biggest problem were the “millionaires” (hinting at the cost), as the Soviets would call them, which were large, complex, and thickly armored bunkers built in the period before the war. For combating these, the most effective way was artillery fire from the massive 152 mm BR-2 howitzer, capable of penetrating 2 m of concrete. However, the system was incredibly large and cumbersome. Transporting the tracked howitzer through the rough terrain was a logistical nightmare.
BR-2 tracked howitzer firing during winter time.
Source: Topwar
The 1930s were a period of considerable maturing of the Soviet armored forces, and the Winter War would be a great testing area for various Soviet tanks, such as the serially built T-26, T-28, and BT-series light tanks, but also various prototype and projects built for the needs created by the war, such as the Object 217 (PPG), SMK, T-100, and KV tank. The KV (U-0) specifically would see action in December 1939. The tank was armed with a main 76 mm L-11 gun and a secondary 45 mm one in a small turret, which was removed on serially produced tanks. After unpleasant experiences with Finnish fortifications, on 11 January 1940, the Leningrad Kirov Plant (LKZ), the builder of the SMK and KV tanks, was asked to develop a tank mounting the M-10 152 mm howitzer. The conversion was made by developing a larger turret on the KV with the M-10T howitzer (the T meaning that the gun was adapted for use in an AFV). It was originally just called KV with a big turret, but was later named KV-2. Several prototypes/early vehicles of the KV-2 would see service against the Finns.
The first KV-2 (KV with big turret) prototype U-3. It was meant to carry a large howitzer for ‘bunker busting’, but the 152 mm M10T was too weak for both concrete and armor penetration.
Source: Juri-rust
Early Bunker Busters
While the KV-2 was being tested in battle, on 17 January 1940, a decree from the Soviet Defense Committee was signed. Plant No.185 was also tasked with continuing their projects on the SU-14 by installing the 152 mm BR-4 inside. The SU-14 was a troubled self-propelled gun project dating back to summer 1933, but due to various reasons, only two were built and tested. The project involved taking the two open-topped self-propelled guns based on the T-35 heavy tank and armoring them, giving them the capability for direct fire from closer ranges, though it was estimated that the average combat range would be between 1.5 to 2 km. The vehicles were given up to 60 mm of armor frontally, increasing the total weight to 64 tonnes, and were renamed to SU-14-2. Despite the progress, the Izhora Plant was only able to deliver the first vehicle by 13 March, a day before the end of the Soviet-Finnish War. The two vehicles were still tested at Kubinka and would partake in the defense of Moscow, but would never enter mass-production.
The only surviving SU-14 (SU-14-2, the armored version shown here) at the Kubinka Tank Museum. It has since been moved to the nearby Patriot Park.
Source: Wikimedia Commons
During the same period, Plant No.185 would not only upgrade its previous SPGs, but also design new vehicles. Their T-100 tank, a competitor to the SMK, would become the basis for heavy gun carriers. Firstly, as a response to the KV-2, the T-100 was fitted with a larger turret and M-10T howitzer and named T-100Z. Additionally, three other projects based on the T-100 were designed to equip the 130 mm B-13 gun, which had a lighter and faster firing shell with similar ballistics. The first two were the T-100X and T-100Y, which replaced the two turrets of the T-100 with a large fixed casemate. The T-100Y was to be built, but it was delivered by the Izhora Plant only on 14 March and thus would not be tested against Finnish “millionaires”. The third project, T-103, was meant to equip the B-13 gun in a large turret, but the project was abandoned after a mock-up was built.
T-100Y, renamed in 1945 to SU-100Y, displayed at Patriot Park.
Source: Patriot Park
Development
The conclusion of the Winter War marked the end of the immediate need for heavy bunker busting vehicles, but they were still seen as a long-term necessity. Thus, on 10 April, testing of the Factory 185’s SU-14-2 and T-100Y commenced. However, due to the archaic chassis of the SU-14 and failure of the T-100 heavy tank, both self-propelled guns were doomed. Attention shifted back to LKZ, and while the KV-2 was a quickly designed vehicle that was forced into service before it was properly tested, it was far from what the Soviet artillery forces needed. The M-10T howitzer had mediocre concrete penetration, 900 to 1,140 mm of reinforced concrete from 1,000 m distance.
On 17 July 1940, LKZ would be tasked with developing a series of new heavy tanks based on the KV tank. In total, there would be four heavy tanks, with 90 mm to 100 mm of armor, as well as being armed with 76 mm and 85 mm main guns. Additionally, a heavy self-propelled gun was also requested, based on the chassis of these new heavy tanks, and armed with the 152 mm BR-2 howitzer.
These heavy tanks would become the T-150, T-220, and T-221, the first two which were built in the fall of 1940 and tested in January-February 1941. The T-220, which was a lengthened KV-1 (seven roadwheels) and 100 mm of armor all around would become the basis for the self-propelled gun.
The T-220, more commonly known as the KV-220, was a lengthened KV-1 with an enlarged turret, housing the 85 mm F-30 gun. It would originally serve as the basis for the Object 212 SPG.
Source: Warspot, colorized by johannes Dorn
It is worth mentioning that, during the same period, the mounting of large caliber howitzers (122 mm, 130 mm, 152 mm, and 180 mm) on the chassis of the SMK was also explored, as a document from 11 June specifically requested the 152 mm BR-2 be mounted on the SMK. Likewise, the idea of mounting the 152 mm BR-2 on the T-100Y was also raised, but by summer 1940, both the SMK and T-100 chassis were dead for good and these plans never went past proposal stages.
On the other hand, the KV-1 and KV-2 would enter full-scale serial production in June 1940 after the implementation of the “Stalin Task”, which demanded the yearly production of 230 KV tanks (130 KV-1s and 100 KV-2s). It seemed as if the KV chassis was the optimal choice for a heavy bunker busting SPG, and there were doubts even about the development of such a vehicle, considering the expected high numbers of KV-2s in the upcoming future.
Development of the self-propelled gun started in August-September 1940 at SKB-4, the LKZ artillery design bureau, headed by P.F. Fedorov, who appointed Ts.N. Golburt as the chief engineer of the project. Design of the hull was done at the SKB-2 design bureau instead, as they had more experience with heavy tanks and designed the KV-220. The self-propelled gun would be based on the Object 212 artillery tractor, and would receive the same name, though some modern resources add the suffix “A” at the end (Object 212A) to make the distinction, though this was never official.
Object 212 Tractor
The original Object 212 tractor was a proposal designed between January and February 1940. It was a 35-tonne recovery tractor on a heavily modified KV chassis, meant to tow knocked-out tanks, as well as for supply and logistics support. The project was never approved for production. It was designed at the SKB-2 design bureau with chief engineer N.V. Khalkiopov. Early blueprints, from 9 February, show that the tractor was to have the final drive towards the front of the vehicle, with the 3 man crew and engine in the center. The rear was reserved for a flatbed for storage. Although derived from the KV tank, all of the components were unique, from the running gear and return rollers, to the hull.
The drawings of the Object 212 tractor, 9 February. Note the new shape and hull components.
Source: Heavy Tank KV
However, by May 1940, the design was changed to use an inverted KV-1 hull, with KV-1 components. The driver was moved to the extreme left of the hull, to allow for the engine and driveshaft. Other small differences, such as the addition of a sprocket guard, were added. Sometime thereafter, a full-scale wooden mock-up of the hull was built. The same general layout was kept as on the earlier tractor. The Object 212 tractor was canceled after the SKB-2 transition to ChTZ.
Front view of the Object 212 tractor, which would serve as the layout inspiration for the Object 212 SPG.
Source: Heavy Tank KVOther view of the Object 212 tractor. Note the 6 roadwheels, as on the KV-1 tank.
Source: Heavy Tank KV
Further Development
The technical drawings of the 212 SPG were completed and signed by Kotin on 5 November, but the 1 December deadline set by the GABTU (Main Directorate of Armored Forces) was not met. Furthermore, LKZ officials Goldburt, Kotin, and P.F. Federov sent a ‘complaint’ letter to the GABTU Artillery Office on the topic of the technical requirements. Firstly, they claimed that keeping the vehicle at a weight below 55 tonnes while still packing 75 mm of frontal armor was not possible. Alternatively, they proposed that the weight threshold be increased to 65 tonnes, but still the vehicle would only receive 60 mm of frontal armor. The Artillery department had to back down and accept these measures.
In a letter dated December 1940 from Major General Slavchenko, Deputy Chief of GABTU, to Lieutenant General T. Fedorenko, Chief of the GABTU, reported the status of self-propelled gun developments at LKZ. Firstly, the first prototype of the Object 212 SPG was projected to be finished by April, with 12 units built by 1 October. Secondly, the mounting of the B-13 130 mm gun on a SPG chassis (likely the same as on the Object 212) was also mentioned, with the first prototype to be complete by 1 May and 12 pieces to be built by 1 November. The 130 mm naval B-13 which had previously been mounted on the T-100 series of heavy SPGs would now get a second chance, being mounted on a KV chassis.
Drawing of the Object 212 SPG. Note that the drawing lacks several details, such as exhaust, rear door, or machine gun.
Source: Warspot, edited
The project of the 212 SPG was completed by January and the drawings and documentation were sent to the Izhora Plant for prototype manufacturing. By 5 March, the Izhora Plant started to deliver components from the same batch as the two T-220 and T-221, but assembly was delayed in a sudden turn of events.
On 11 March, the Soviet intelligence services submitted a report on German tank developments, which included the alleged design of a Mark VII heavy tank, with 105 mm gun and 90 tonnes of weight (Pz.Kpfw.VII Löwe). Other heavy tanks included the Mark V and Mark VI heavy tanks, with weights of 36 and 45 tonnes respectively. The Soviet officials scrambled towards designing a Soviet equivalent, and thus the KV-4 (Object 224) began its development, with a weight of 75 tonnes and 107 mm main gun.
On 7 April, more heavy tanks were proposed, namely the new KV-3, also known as Object 223, which used the hull of the T-221 (up-armored to 120 mm) and an entirely new turret and 107 mm gun. Lastly, a 100 tonne heavy tank with 170 mm of frontal armor was also requested, the KV-5 (Object 225).
As the new KV-3 was to essentially replace the T-220, while still having an nearly identical hull (the only difference was the 120 mm of armor instead of 100), the Object 212 SPG would now reuse the hull of the KV-3, though no major changes were required.
Mock-up of the KV-3 (Object 223) on which the 212 SPG would be based on later.
Source: Warspot
From Bunker Busting to Lion Hunting
In wake of the German heavy tank developments, Marshal of the Soviet Union G.I. Kulik would send a letter on 17 April to Stalin. Kulik, who was supervising work at LKZ, claimed that the BR-2 gun on the Object 212 in development could be used against heavily armored tanks effectively, penetrating 155 mm of armor at 2,300 m. Likewise, he mentioned the development of the self-propelled gun armed with the 130 mm B-13, but this time on the lengthened chassis of the KV-4. An unspecified high-power 107 mm gun was also under consideration.
It must be noted that the KV-4 Marshall Kulik mentions was likely a mistake or confusion on his part and could not have been the KV-4 super heavy tank, the design of which was not completed until early May. The two SPGs with 130 mm and 107 mm guns were to be built by 1 September and 1 October respectively. This is confirmed at the end of Kulik’s letter, which states that the two tank destroyers were to use the same chassis as the 152 mm howitzer variant (Object 212). Lastly, Marshall Kulik mentions that the original Object 212 prototype would have to be finished on 1 June, allowing for production for the remainder of the year. Another option is that Kulik simply misspelled or confused the KV-3 and KV-4. Realistically, the KV-4 would wind up being so large there was no point in enlarging it for mounting these bigger guns. Likewise, an SPG based on it would have weighed far more than 55 tonnes, considering that the heaviest KV-4 design, by G.V. Kruchyonyh, weighed 107 tonnes, and the lightest, designed by N.L. Dukohv, weighed ‘just’ 82.5 tonnes.
The SPG armed with the 130 mm B-13 was to have a weight of 55 tonnes and thus be lightly armored, at only 30 mm all around the casemate, with adequate protection against shrapnel and diving aircraft attacks. This vehicle is commonly known today as the SU-B-13, though it was not an official name.
The other vehicle was also meant as a tank destroyer and to be equipped with an unspecified high power 107 mm gun, likely the ZiS-24 or M-75, but the vehicle never went past the proposal stage.
Regarding developments on the Object 212, activity was stagnant from March to April. On 27 May, it was confirmed that the 212 SPG would now use the KV-3 (Object 223) chassis instead of the T-220. Whether this means that the Object 212 SPG would have inherited the KV-3’s 120 mm of hull armor as opposed to the original 100 mm on the T-220 is unknown. Delivery of the first prototypes was once again postponed to August, with 12 vehicles to be built and later cut down to 10.
On 30 May, a report on the costs of KV heavy tank projects was published, and here, the 212 SPG was mentioned. In total, it cost 2 million rubles, the equivalent price of four KV-1 mod.1941 tanks.
Stage of Object 212 SPG Development
Price (thousands of rubles)
Draft drawings
100
Scale models
25
Technical drawings
300
Prototype construction and factory trials
1100
Proving ground trials
100
Drawing correction after trials
75
Repair of prototypes and improvements
300
Total cost
200
Source: CAMD RF 38-11355-101
Design
The design of the Object 212 self-propelled gun was very different from any previous vehicles, as it was based on the combination of 212 tractor and the T-220 heavy tank. As remnants of the 212 tractor, the engine and final drive were in the front of the hull, with the idler towards the rear. The platform that was previously used for transport was lengthened, as the chassis was now borrowed from the T-220, and fitted a very large armored casemate, housing the crew and the BR-2 howitzer.
The vehicle is claimed to have resembled the SU-14 in terms of general design, but it might just be pure coincidence. Mounting a large howitzer and its crew towards the rear of the hull offers more internal room, better recoil management, and less frontal gun overhang.
Cutout view of the 212 SPG showcasing the internal components. The gunner’s ‘cupola’ on the casemate roof and ammunition stowage on the hull floor are noteworthy.
Source: Warspot, editedExternal view of the hull and several joints of the armor plates.
Source: Warspot, editedInternal view of the hull with specific joints and structural supports. Note the large gun frame in the hull.
Source: Warspot, edited
Crew
The exact crew details were never specified, but based on the type of vehicle, at least seven men were required: commander, driver, radio operator, two gunners, and two loaders. Although the BR-2 field howitzer used a crew between 10 and 15 men, a lot of this manpower went to preparing the vehicle for transport, ammunition supply, and other logistical difficulties, which would not exist on a self-propelled chassis. Furthermore, a larger crew would have been unbearable in the large, but enclosed casemate.
The driver was positioned to the extreme left of the chassis, to the left of the driveshaft, as opposed to the center on the KV-1, due to the engine and driveshaft now occupying a large volume inside the hull. The radio operator likely sat behind the cooling system and operated a 71-TK-3M radio. The tank commander and the gun operators would stand in the casemate. The commander would have a slightly elevated ‘cupola’ with a PTC rotating periscope for vision, to the right of the gun. The main gunner would sit on the left side of the gun and had 3 fixed periscopes, main gun periscope, and a PTC rotating periscope, for a total of seven periscopes in the casemate. For self-defense, four firing ports were made on the side walls and one 7.62 mm DT machine gun was mounted in a ball mount on the rear wall. For entry and exit, two to three hatches were mounted on the top, as well as a door on the rear wall, for easy entry/exit and ammunition resupply.
Propulsion
The 212 SPG had a V-2SN, a centrifugally supercharged variant of the standard V-2 12-cylinder diesel engine, outputting 850 hp. It was developed by Plant No.75 for the T-220 heavy tank. During its testing on the tank in January-February 1941, the engine was still unfinished and would prove to be a disaster. It lasted for 5 hours and 51 minutes or 106 km on the nearly 63 tonne heavy tank, the tank reaching a top speed of 21.2 km/h. Fuel consumption was 15.5 liters per hour or 0.83 l per 1 km. Wearing out of the pistons squirted hot oil and led to power loss, stopping the trials. Due to the lack of a spare engine, the trials were terminated.
The 700 hp V-5 mounted on the T-150 would suffer a similar fate, but with slightly better results. Due to the engine plant’s inability to provide engines for the new heavy tank projects, the trials of the T-150 and T-220 were postponed until Plant No.75 could fix these issues.
The KV-3 (Object 223) heavy tank, which would become the chassis for the 212 SPG when the T-220 was canceled, was also meant to equip the same engine.
The fuel tank capacity on the 212 SPG was of 845 liters, for an estimated road range of 200 km.
Multi view drawing of the V-2SN engine installed on the Object 212 SPG.
Source: Warspot, editedCutout view of the engine compartment, showing the final drive, engine to the right of the hull, driver’s position to the left and cooling system behind him.
Source: Warspot, edited
Main Armament
The most important element of a self-propelled gun is its main armament. For the Object 212 SPG, this was the 152 mm BR-2 Model 1935. The field gun counterpart was particularly controversial. It weighed over 18 tonnes, had a maximum road speed of 15 km/h, and took a 15 man crew 25 minutes to set it up from marching position into firing position with maximum firing elevation. Additionally, by the start of the invasion of the USSR, only 37 pieces had been built, of which only 27 were in active service. Other concerns were the poor horizontal traverse of just 8° towards each side and 100 round barrel life. The latter was fixed in 1937 with deeper riflings. The gun would still see intensive use, from the Siege of Leningrad all the way to shelling Berlin. After modernisations in the 1950s, the guns would be used all the way into the 1970s. The rate of fire was a standard 1 to 2 rounds per minute and maximum range was around 25 km.
The advantages of mounting this cumbersome but otherwise very powerful gun on a tank chassis were obvious, hence the Soviet Artillery department’s wishes for one. The low towing speed and long setup time could be vastly improved, while the thick armor of the vehicle would allow for flexibility in operation, whether it would be close-range support or indirect fire.
However, the mounting of the gun inside an enclosed casemate would have certain negative side effects. Firstly, the tight operating space could have decreased rate of fire and made it a cramped space to be in, but still better than being exposed to the elements and enemy counterbattery. Additionally, as seen on the SU-14, a casemate significantly decreased the elevation angle of the gun, from 60° to 30°, while in the case of the Object 212 SPG, it decreased to just 15°, making indirect fire virtually impossible. This was not seen as an issue, as the vehicle was meant for direct fire support. Gun depression was -3°.
The vehicle was equipped with a respectable 47 two-part rounds for the main gun. In comparison, the SU-152 had 20 rounds. The shells were stowed in the rear corner of the vehicle floor, as well as on the casemate sides. Loading was assisted by a bracket for resting the rounds on. Ammunition for the single 7.62 DT machine gun was 3,000 rounds.
Comparison chart of the KV-2 and Object 212 SPG main guns
Name
M-10T
BR-2
Caliber
152.4 mm
152.4 mm
Muzzle velocity m/s
400-500
880
Shell weight
40 kg
49 kg
Explosive weight (kg TNT)
5.3-5.8
6.5 -7
Penetration (armor)
72 mm @ 60° from 1,500 m
155 mm from 2,300 m
Penetration (reinforced concrete)
900-1,140 mm from 1,000 m
1,500 mm
Komintern tractor pulling the BR-2 howitzer in the transport configuration during a parade.
Source: Topwar
Br-2 152 mm Howitzer on Turreted KV Chassis
Sometime during spring 1941, Kotin, with SKB-2 engineers L.E. Sychev and A.S. Ermolaev, went on a day trip to study naval guns of ships at the Baltic Fleet. There, they inspected the battleship Marat and a Kirov-class cruiser, as well as various other ships. Several systems were analyzed, including gun mounts, loading systems, and ammunition stowage mechanisms. The goal was to incorporate naval guns on tank chassis. One of these projects was mounting the Br-2 152 mm howitzer inside an armored turret and onto a KV chassis (likely also KV-220/KV-3).
Unfortunately, not much is known about this project, aside from the recollections from SKB-2 engineer, K.I. Buganov:
“Before the war, we worked on a hull for a self-propelled artillery installation based on KV with the placement of a 152-mm Br-2 naval gun in its armored turret. The car turned out to be two tons heavier than the calculated one, and Joseph Yakovlevich asked me: “Do you have any proposals for weight reduction?” I said, if you reduce the distance between the engine and the gearbox, you can reduce the length of the car by 500 mm. Reduce the length of the sides, roof, bottom, tracks, and this will give great weight savings. Joseph Yakovlevich said only one word “good”, and then instructed to rework the drawings, regardless of the fact that tracing papers had already been released, that is, essentially the work had ended. Joseph Yakovlevich always quickly grasped the main thing, and if he saw a technical benefit, he never stopped before the difficulties of rework.”
Unfortunately, no drawings of the vehicle are known to survive. The project likely did not survive summer 1941, and was undoubtedly a very challenging feat to fit the Br-2 in a rotating armored turret and still be capable of firing.
Fate
The German invasion of the Soviet Union on 22 June did not have much effect on the 212, which had effectively been frozen in development for nearly 5 months. An attempt to cancel the project would infuriate the head of the Artillery Department, Colonel-General V.I. Khoklov, which after one-and-a-half years, still did not get an improvement over the KV-2 in terms of direct fire bunker busting.
By August, the German forces were approaching Leningrad, the city where LKZ was based and so most of the engineers and projects were transferred to ChTZ in Chelyabinsk, which would be renamed to ChKZ (Chelyabinsk Kirov Plant). Some tank projects were canceled, like the KV-4 and KV-5, while the KV-3 was to continue development at ChTZ. The prototypes of the KV-220 and T-150 would be pressed into combat service at such a desperate time.
The Object 212 had a different fate. It was transferred to the Ural Heavy Engineering Plant (UZTM) in modern day Yekaterinburg. The design bureau, headed by F.F. Petrov, had plenty of experience on artillery pieces and just started producing KV-1 tanks as a subcontractor to ChTZ. On the other hand, this was their first encounter with a tracked SPG project. A.S. Ryzkhov was appointed Head of the Object 212 project.
In October, UZTM sent a letter to ChTZ requesting material and components of the KV-3 to be able to start concrete work on the 212 SPG. The problem was that ChTZ was not working on the KV-3, which had been transferred from LKZ, but it was frozen.
The Object 212 would have its final breath in November 1941, when it was noticed that the switch from tractor production to KV production at ChTZ would mean no more tractors to tow artillery, and thus self-propelled guns were necessary, of which the Object 212 was first mentioned.
However, by December 1941, the KV-3 was virtually canceled and focus at ChTZ went towards other vehicles. Without the enlarged hull of the KV-3, UZTM could not build a prototype and the project was canceled as well.
Interestingly, in March 1942, Experimental Plant No.100 was appointed to design and develop a 152 mm BR-2 heavy self-propelled gun on a KV chassis, the bunker buster. Plant No.8 was responsible for the gun mount. 1,500,000 Rubles were assigned to the project, but the death of the KV-3 and complexities of lengthening the KV-1 chassis doomed it as well.
Various heavy self-propelled gun designs on KV chassis would be drawn out in the following period by several design bureaus, but it was not until 1943 that the Soviets could field one, in the form of the SU-152, armed with the ML-20S 152 mm howitzer mounted on the KV-1S chassis.
Conclusion
The Object 212 was a very promising project on paper. The ability to improve the BR-2 howitzer’s main drawbacks and mount it on an armored chassis would have proven very beneficial. However, the project was on a rough route right from the start. The end of the war with Finland meant that there was no immediate need for such a vehicle, while the mass-production of the KV-2 could (on paper) fulfill the same role already. Lastly, the vehicles it was intended to be mounted on, the T-220 and KV-3, were too heavy and unreliable, and with the start of the war with Germany, the Soviets could not afford to spend time and resources on uncertain projects. The need for a self-propelled gun armed with a potent 152 mm howitzer would persist well into the war, until the SU-152 would enter service.
Object 212 SPG illustrated by Pavel ‘Carpaticus’ Alexe
Object 212 SPG Specifications
Dimensions (L-W-H) (approx.)
7.90 x 1.92 x 2.57 m
Total weight, battle-ready
65 tonnes (50 tonnes without ammunition, fuel and equipment)
Crew
7 (Commander, driver, radio operator, 2x gunners, 2x loaders)
Soviet Union (1941)
Heavy tank – Partial Mock-up Built
Even before the T-150 heavy tank entered trials in January 1941, several issues had already been noted and a new turret was designed. Nonetheless, this turret never left the drawing board. A second attempt was made during and after the T-150 trials, and the tank was named Object 222. After impressing the military and state officials, it was named KV-3. The excitement was short-lived, however. In April, heavier tanks, like the Object 223, were designed, and this latter project would eventually get the name KV-3 as well. The Object 222 was then meant to enter production in June 1941, under the name KV-6, but, due to the German invasion of the Soviet Union, this never happened.
The T-150
The KV-1 heavy tank would officially enter production in February 1940, 9 months after the original request for production. Even so, by July, only 32 of the pre-series KV tanks were built, prefixed with the “U” index. The tanks had design issues, along with technical and production problems. The pressure from Stalin to adopt these unfinished tanks grew, and, in June 1940, with the “The Stalin Task”, the Council of People’s Commissars of the Soviet Union would order the increase of the yearly production quota of the KV to 230 units of both variants (130 standard KV-1 and 100 KV-2s with 152 mm howitzers). The Leningrad Kirov Plant (LKZ), barely able to keep up with the previous production rate, was ravished. Corners had to be cut in order to streamline and speed up production, while the tanks were still being tested and improved on the go. This cutting of corners would later come to bite the Soviet officials and factory designers in the back, as the KV-1 would prove to be unreliable and cumbersome on the battlefield.
The desire for heavier tanks based on the KV-1 appeared in May 1940, and by 17 July, the Main Directorate of Armored Forces (GABTU) and the People’s Commissariat of Heavy Engineering requested four new tanks from LKZ, more specifically the SKB-2 design bureau. Out of these four tanks, two were to pack 90 mm of armor, of which one armed with a 76 mm gun and one with an 85 mm gun. The other two were to have 100 mm of armor and also be equipped with a 76 mm and 85 mm gun respectively. The latter would become the T-220.
For the 90 mm armor tank with 76 mm gun, the chief designer, Military Engineer L.N. Pereverzev, part of the SKB-2 design bureau, was assigned to design it by August 1940. The new tank was indexed T-150, but the Object 150 and KV-150 names were also officially used. It was to be based entirely on the KV-1 in production, with only the necessary changes made. In order to add the extra 15 mm of armor all around the tank, it was necessary to equip it with a new engine, namely the 700 hp V-5 from Plant No.75. As the thickening of the armor was done outwards, the internal layout and components position of the KV-1 were kept the same. Reinforcements were added to the suspension to better deal with the extra mass, which reached 50.16 tonnes, compared to the 44 tonne KV-1 (autumn 1940). Lastly, and perhaps the largest external change on the T-150, was the addition of a large commander’s cupola, equipped with 6 periscopes and one rotating PTC periscope.
The T-150 was a premature attempt at improving the armor of the KV-1, which was already excellently well armored.
Source: Warspot, colorized by Johannes Dorn
The first prototype was to be built and delivered to LKZ by the Izhora plant by 1 October, but due to overloading difficulties caused by the KV-1 production, the prototype was only delivered by 1 November. During November, after analysis by its designers, a new turret for the T-150 was designed, that would fix certain problems annotated, like the poor commander’s position to the right of the gun. In the new turret, the commander was moved to the back, inside the turret bustle, where he would have a better overview of the battlefield, with 8 periscopes instead of 6, and better communication with the crew. Another problem fixed was the removal of the gunshield above the mantlet, which on the T-150 prototype was poorly made and restricted gun depression. Despite these promising changes, it did not go past the blueprint stage.
Testing of the T-150 would begin on 14 January 1941 and end in February. During this period, several significant issues were discovered. Firstly, the T-150 weighed 50.16 tonnes, over 2 tonnes heavier than the 48 tonne threshold imposed by the GABTU. Secondly, the experimental V-5 engines would prove to be a complete disaster. The chief designer of Plant No.75, T. Chuptakhin, who was present at the trials, was not able to guarantee the operation of the engines installed on the T-150 and T-220 tanks. The T-150 would only operate for 24 hours or 199 km before its engine broke down. It was noted that when driving in high gears (3rd and 4th gear), the injected oil temperature would spike after just 5 minutes even in outside temperatures of 9-12º Celsius.
The turret would prove problematic as well, despite the issues originally being noticed in November. The commander’s cupola was too tall for observation while sitting down, but too low when standing up, forcing the commander to semi-squat in a very straining position. The other crewmembers in the turret were not spared of problems either. The loader, sat behind the commander and to the right of the gun, would be restricted from lifting shells from the left wall by DT machine gun ammunition boxes. The vast majority of the main gun shells were stored in small boxes, which were hard to open, cutting the loader’s hands and getting stuck on one-another. This decreased the rate of fire to 1-2 rounds per minute when loading from the boxes (from 5-7 rounds per minute maximum). Lastly, the gunshield above the mantlet was badly designed and only allowed for 3º of gun depression, instead of the 6.5º intended.
All in all, the T-150 performed as expected considering the rough circumstances, and many of the issues could be roughed up. Despite this, the GABTU and People’s Commissariat of Heavy Engineering were not satisfied with the result and demanded that the turret and engine problems be fixed.
The November 1940 sketch for an improved turret for the T-150. This turret would become the basis for the turret of the Object 222.
Source: Warspot
Development
Before the T-150 trials were even finished, a second attempt at improving the turret was made. Like the first time, the commander’s position was moved to the turret bustle, with a more streamlined cupola, which dropped the PTC rotating periscope but maintained the eight periscopes, as opposed to the T-150’s six. Other changes included the casting of the gun mantlet for faster production, removing the side turret wall gun port and decreasing the size of the gunshield. One of the more controversial changes was the adjusting of the side and rear wall armor to vertical angles, as opposed to 15° inwards. Otherwise, the design would use the same hull as the original T-150. The tank was indexed Object 222.
After review of the project by the GABTU and state authorities, the People’s Commissariat of Defence and the Central Committee of the Communist Party proposed accepting Object 222 into service and giving it the name KV-3. The name KV-3 had previously been used when describing the T-150. The question of propulsion was also raised, but after a commission formed on 21 February, Plant No.75 had to figure out the issues with its engines and make them usable by 10 April. To ensure that the engine would not overheat again, the cooling system of the Object 222 was reworked as well.
The Object 222 was still armed with the 76 mm F-32 gun, but with the same gun being introduced on the KV-1, it seemed like it would quickly become redundant. Thus, it was also proposed that the Object 222 (KV-3) was to be rearmed with the much more potent 76 mm F-34.
On 3 March 1941, a commission was formed, consisting of Military Engineers 2nd Rank I.A. Burtsev and I.A. Shpitanov, Military Engineer 3rd rank Kaulin, LKZ director I.M. Zaltsman, SKB-2 director J.Y. Kotin, director of LKZ 1st dept. A.Y. Lantsberg and NII-48 research institute engineers V. Dalle and A.P. Goryachev. The goal of the commission was to further assess the Object 222 and prepare it for prototype production. The commission reviewed the drawings of the tank as well as a wooden mock-up of the turret mounted on the hull of the KV-1. It was here that the lack of an angle on the side and rear plates was deemed as an issue, decreasing the overall armor protection. Other issues noted was the lack of an entry and exit hatch on the commander’s cupola and vulnerability of the pericopes from damage and enemy fire.
Nonetheless, the commission agreed on producing a turret as per the above in order to have it ready for testing by 1 April. Yet the commission would expect that, by the time of mass production, the turret walls would be angled again. According to the three representatives from LKZ, Zaltsman, Kotin and Lantsberg, the reasons for implementation of vertical walls were:
Improving crew working conditions;
Improving connections between the plates, especially for the roof plate;
Easier manufacturing.
Additionally, they claimed that the sloping brought no true advantages either. Mathematically, the equivalent armor thickness of a 90 mm plate angled at 15° is 93.17 mm, an insignificant gain considering the production complications.
After the commission, on 15 March, the Council of People’s Commissars of the Soviet Union and the Central Committee of the Communist Party gave decree No. 548-232§, which imposed that LKZ had to switch mass production to the KV-3 (Object 222) in August, with 55 units built in the first month, increasing to 105 in September, 110 through October and November, and 120 units in December, for a total of 500 KV-3 tanks in 1941.
The date of delivery was also pushed back after LKZ’s ‘complaints’, and the first prototype was to be delivered by 1 May, and testing to begin on 15 May. To meet this deadline, the Izhora plant had to deliver the experimental turret by 1 April, with LKZ having to deliver drawings of the experimental turret on 20 March, drawings of the hull by March 25 and drawings of the production turret by 10 April. Plant No.203 to deliver the KRSTB radio set and Plant No.69 to deliver optical sights for the DT machine guns.
Design
The Object 222 (T-222/KV-3) was just a T-150 hull with a slightly modified turret. In turn, the T-150’s hull was just a KV-1 hull with a new engine and minor dimension changes due to the thicker armor. The frontal upper plate consisted of two parts, an angled ‘hood’ and a flatter portion, right in front of the driver and radio operator. On it was the headlight, driver’s vision port, and a 7.62 DT machine gun in a ball-mount. Above, on the top deck was a service hatch for the two crewmembers. The running gear consisted of a frontal idler, large rear sprocket, and 6 steel rimmed wheels, sprung by torsion bars, with three return rollers.
The general armor profile was of 90 mm all around, with the exception of the turret roof, which was 40 mm thick, and hull deck, which was 30 mm. With the new turret, the weight of the Object 222 was expected to be slightly higher than that of the T-150, at 51 to 52 tonnes.
The side drawing of the Object 222, armed with the 76 mm F-32 gun, circa February 1940.
Source: Yuri Pasholok
Turret
The new turret differed greatly from the T-150’, but was heavily inspired by the November 1940 T-150 turret upgrade. The gun mantlet was a two-part cast type, and the gunshield was shorter, for improved gun elevation and depression angles. The design of the turret walls was altered as well, with larger flat side and rear plates and potentially a rear turret door, like on the KV-2 and T-220, though this is unconfirmed. The rear-facing 7.62 mm DT machine gun mount was kept, though the ball-mount design was changed as well. Other minor changes to the turret included strengthening around the gun mantlet side-front plate connection and the replacement of side gun port and vision slit with a small hatch.
The most important change was the relocation of the commander, to the back of the turret. The position of the T-150’s commander was noted as an issue already in November 1940, thus the first turret upgrade design also placed the commander in the back. Likewise, the trials of the T-150 criticized the position of the commander and suggested moving him to the rear. However, after the commission analysis of the Object 222 turret, it was not deemed as ideal. Additionally, the lack of an entry-exit hatch for the commander and no protection ring for the periscopes were also deemed as an issue. To fit the commander in the turret overhang, a large groove was made along the connection between the turret ring and the turret overhang bottom plate, to allow the commander to sit on.
Internal cutout view of the Object 222. Note the position of the F-32 gun ammunition in the turret bustle.
Source: Stalin’s Supertanks IS-7
Crew
The crew consisted of 5: commander, gunner, loader, driver, and radio operator. The commander sat in the turret bustle, from where he could communicate with the loader and gunner. For vision, he had a cupola with 8 periscopes. He would also operate the rear facing machine gun, should the situation call for it. The gunner sat to the left of the gun, and had his primary gun sight and a PTC rotating periscope for general vision. A second fixed periscope was placed on the side of the turret, like on most KV tanks. The loader sat to the right and rear of the gun, and would load shells from both sides of the turret walls and those stowed in the hull floor. He was no longer responsible for the rear-facing machine gun.
The positions of the crew in the hull was unchanged from the KV-1, with the driver in the center and the radio operator to his left. The radio was a KRSTB, an early version of the 10-RT radio, but it was possible to install the standard 71-TK-3 radio.
Commander’s position on the November 1940 turret upgrade of the T-150. Some of the changes were incorporated into the Object 222.
Source: Warspot
Propulsion
The engine of the Object 222 was to remain the V-5 engine, as on the T-150, but in a functional form and with a redesigned cooling system. The V-5 engine had been developed at Plant No.75 by boosting the V-2K 600 hp engine, which itself was an already boosted and unreliable variant of the V-2. The V-5 was a four-stroke 12-cylinder diesel engine outputting 700 hp. The fuel tank had a 700 liter capacity, offering the tank a range of 250 km or 10 work hours. Maximum speed was a mere 35 km/h on road and off-road, 15 to 20 km/h. The tank had a warranted distance between major breakdowns of 2,000 km.
Armament
Initially, the main armament was to remain the 76.2 mm F-32, as on the original T-150 and which just began incorporation on serially produced KV-1s, replacing the L-11 gun. But during discussions in February, it was proposed to rearm the Object 222 with the much more potent 76.2 mm F-34. The tank carried 114 shells for the 76 mm gun and 2900 rounds in 46 drums for the DT machine guns. The main difference between the F-32 and F-34 guns was the muzzle velocity and penetration. For example, the same shell, BR-350A (APHE) had 615 m/s muzzle velocity in the F-32 and 662 m/s in the F-34. Likewise, the OF-350 (HE) had 615 m/s muzzle velocity on the F-32 and 680 m/s on the F-34. The F-34 gun was mounted on the T-34 tank in early 1941, with the KV-1 adopting it only much later as the ZiS-5 gun.
F-32
F-34
Caliber (mm)
76.2
76.2
Muzzle velocity (m/s)
615
662
Shell weight (kg)
6.3
6.3
The tank was armed with two 7.62 DT machine guns, one in the hull for the radio operator and one in the back of the turret. The KV-1 and T-150 also featured a coaxial machine gun, but it was dropped on the Object 222, as the commander was moved and due to the new gun mantlet.
Fate
Between 7-9 April, the LKZ heavy tank development programs were altered, as the need for more powerful heavy tanks was assessed. The KV-3 name would be given to a new tank, based on the up-armored chassis (120 mm frontal armor) of the Object 221, and named Object 223, as well as receiving an entirely new turret armed with the 107 mm ZiS-6. Furthermore, a 100-tonne tank was also requested, with 170 mm of frontal armor and also armed with the 107 mm ZiS-6 and was named KV-5 (Object 225). The LKZ factory was still meant to build a prototype and begin prototype production by June, but with three heavy tank developments ongoing simultaneously with tight deadlines. Based on the production quota report for LKZ, 500 KV-3 (Object 223) tanks should have been built from August 1941 to the end of the year.
The KV-3 (Object 223). Despite also being named KV-3, the Object 223 was a serious upgrade over its predecessor.
Source: Warspot
On 5 May, Marshal G.I. Kulik and Lt. Gen. Y. Fedorenko came to the Central Committee of the Council of People’s Commissars of the Soviet Union, requesting the switch to the KV-6 (Object 222) as opposed to the KV-3 (Object 223). Historian Maxim Kolomiets also mentions here that the KV-6 was also armed with a flamethrower with 15 rounds (10 liters) and that the vehicle was actually the T-150, though that is improbable.
The situation worsened on 22 June 1941, when the Axis forces began Operation Barbarossa, the invasion of the Soviet Union. Thus, much of the military’s focus shifted to producing, maintaining, and improving existing tanks. Furthermore, by September, German forces were approaching the city of Leningrad and many SKB-2 engineers were evacuated or placed into military maintenance battalions. Those evacuated were sent to the Chelyabinsk Tractor Plant (ChTZ) which was renamed ChKZ (Chelyabinsk Kirov Plant) after this move. Work on the KV-4 and KV-5 would not resume, but the KV-3 would continue to see slow development until December, when it was finally canceled.
The Object 222, (KV-6) would be ordered to start production at ChTZ on 1 January 1942, with LKZ and NKTM officials providing a prototype, while ChTZ sends a team to LKZ to establish the technical details of the design and prepare for its production.
Conclusion
The first KV-3, the Object 222, was just a T-150 with a new turret. Unlike its predecessor, it was much more short-lived, damned by the design and developments of much heavier KV tanks. With hindsight, the Object 222 was a genuinely good design on paper, and a mature improvement of the KV-1. Sadly, the Object 222 remains overshadowed to this day by more ‘exciting’ designs, like the T-220 and Object 223, the latter KV-3. Only a turret mock-up was built, which was likely destroyed during the war.
Object 222. Illustration by Pavel Alexe.
Object 222 (T-222/KV-3/KV-6) Specifications
Dimensions (L-W-H) (approx.)
6.760 x 3.330 x 3.010 m
Total weight, battle-ready
51 – 52 tonnes
Crew
5 (Commander, gunner, loader, driver, radio operator)
Propulsion
V-5 12-cylinder diesel, outputting 700 hp.
Speed
35 km/h
Suspension
Torsion bar, 6
Armament
76.2 mm F-32 or F-34
3x 7.62 mm DT machine guns
Armor
Front/sides/rear of hull and turret: 90 mm
Top/Belly: 30 to 40 mm
Soviet Union (1940-1943)
Heavy Tank – 1 Prototype Built
The KV-150, or more commonly named T-150, was an attempt to improve the armor of the KV-1 even before the KV-1 entered mass production. With 90 mm of armor all around and a 700 hp engine, it could have been a better option had it not been for some critical events during its development phase. It was, however, groundbreaking in what would become a series of KV heavy tanks, and the single prototype saw combat service until the end of 1943.
The KV-1
As one of the most iconic and recognizable tanks of the Second World War, the KV-1 (or simply KV, acronym for the People’s Commissar of Defense for the Soviet Union, Kliment Voroshilov), proved to have unmatched armor and a very potent gun at the start of the German invasion of the Soviet Union, on 22 June, 1941. It had been developed in the late 1930s and tested in combat alongside its 2 much larger competitors, the SMK and T-100, during the Winter War. As the latter 2 followed a much more complex and archaic breakthrough tank philosophy, namely multi-turreted “landships”, the KV-1 (at the time U-0) would be selected for further development. It was created at the Kirov Leningrad Plant (LKZ), where the previous T-28 and its own competitor, the SMK, were designed and built.
By 19 December, 1939, production of 50 KVs was ordered, with mass production to begin in 1941. But, during this time, the ugly side of the vehicle started to come to light. Truth is that, by that time, the KV was far from ready for production, and dozens of mechanical problems, mostly caused by the heavy weight, had to be sorted out. However, due to Stalin’s personal involvement and pressure on the project, the KV entered preseries production in February 1940, which were indexed with a “U” prefix. These differed from vehicle to vehicle and were tested thoroughly to diagnose any issues.
The first KV, the U-0, which would be tested in combat on the Karelian Isthmus in December, 1939.
Source: Topwar
Naturally, Stalin’s patience would not last, and in June 1940, in what would be called “The Stalin Task”, a decree from the Council of People’s Commissars of the Soviet Union would increase the yearly production quota of the KV to 230 units of both variants (130 standard KV-1 and 100 KV-2s with 152 mm howitzers). This immediate increase in production strained the LKZ plant into mass producing what was effectively an unfinished tank. Naturally, corners and compromises had to be cut over all fields in order to streamline production and cut costs. As some KVs were built, others were still vigorously tested, and results showed that the reliability of the gearbox and transmission were poor. Although changes were made, this aspect would become the bane of the KV-1’s existence. From February to July, 32 KV tanks had been built, and production would increase to 20 during the month of August and 32 during September.
A KV-1 built during August or September 1940, abandoned during early stages of the Great Patriotic War. It is armed with the 76 mm L-11 gun.
Source: Waralbum.ru
More Armor
As early as May 1940, before the KV-1 even entered its shy mass production, the topic of improving the armor of the KV was discussed both by the GABTU (Main Directorate of Armored Forces) and by the People’s Commissariat of Heavy Engineering, where the LKZ plant was represented at. First mentions of thickening the KV tank’s armor came on 11 June, which claimed the need to up-armor the tank to armor between 90 and 100 mm. Furthermore, on 17 July, 1940, the Council of People’s Commissars of the Soviet Union adopted decree No. 1288-495cc, which stated:
By November 1, 1940, the Kirov Plant will produce two KV tanks with 90 mm of armor: one with a 76 mm F-32 gun, the other with an 85 mm gun. The Izhora Plant will deliver one hull at the end of October, the production of the tank is scheduled to be completed by November 5. The second hull will be made by November 5th.
By December 1, 1940, the Kirov Plant will produce two KV tanks with 100 mm of armor: one with a 76 mm F-32 gun, the other with a 85 mm gun. One hull will be delivered by the end of October and by the end in November.
In comparison to its predecessor, the KV-1, as being built in summer-autumn 1940, had 90 mm around the gun mantlet and 75 mm all around. These were exquisite levels of armor not just for Soviet tank standards, but also internationally, being able to withstand most anti-tank guns. It also put the weight of the KV at 44 tonnes, already a tonne increase from the U-0. The weight of the KV would keep on increasing, peaking at 47.5 tonnes by 1941.
Regarding the armament mentioned in the decree, the KV-1 was equipped, as a stopgap measure, with the L-11 76 mm gun until mass production of the more potent 76 mm F-32 could begin. As for the 85 mm gun, it was likely to be the F-30 gun developed by V.G. Grabin at plant No. 92 in Gorky, based on the 85 mm M1939 52-K. However, it is noteworthy that only one such gun had been built, and its testing had yet to conclude.
The first obstacle that the up-armored KV faced was the KV itself. By July, the design bureau tasked with its development, SKB-2 and the entire LKZ factory were busy producing and improving the KV, with little room to spare for a new development. The situation was worsened by the delayed delivery of the tank requirements from the military to SKB-2.
Joseph Yakvolevich Kotin, head of SKB-2’s design bureau and one of the greatest heavy tank designers of the Soviet Union.
Source: Andrei BT
In August, head of the SKB-2’s design bureau, J.Y. Kotin, made two teams for the development of the two tanks. The 90 mm-armor KV was to be designed by a team led by Military Engineer L.N. Pereverzev and indexed as T-150 or Object 150 / KV-150. All 3 names were used in documents. For the sake of simplicity and consistency, it will be called T-150 in the article, with the exception of direct document translations. At this point, Pereverzev was still rather new to SKB-2, having just graduated from the Military Academy of Mechanization and Motorisation of the Red Army in 1939, and had only worked on the KV-1.
After the start of WWII, being a military officer, Leonid Nikolevich Pereverzev was put in charge of the 22nd Mobile Repair Battalion, dispatched from LKZ, focusing on KV tanks. By the end of the war, he had received a variety of medals and orders for his efforts during the war. In his short tank design career, he had worked on the KV-1, T-150, T-220, KV-3, and KV-4.
Source: Yuri Pasholok
For designing the 100 mm-armored KV, the more experienced L.E. Sychev was appointed as chief designer. This variant would be indexed T-220 or Object 220 / KV-220. Sychev was a tank design veteran. He had worked on his bachelors at SKB-2 and then began his career in the same place, working on the T-28, SMK, and KV-1.
Once SKB-2 had sent over the documents (likely in September 1940) to the Izhora plant, the T-150 faced another issue. The Izhora plant was working at a very high capacity trying to increase its KV tank output. The 4 prototype KVs were to be built at Hall No.2, where 4 KV tanks were already being built at the same time. This meant that the October 1 deadline for the T-150 was missed, but not by much.
The Izhora plant delivered the hull of the T-150 and a turret on November 1 and LKZ completed the prototype by December. The T-220 was completed shortly after.
The T-150 after it was completed (December-January). Externally, it looked like a KV-1, with the main difference being the commander’s cupola.
Source: Warspot, colorized by Johannes Dorn
In November, during the latter stages of the development of the T-150, a new turret was proposed. It moved the commander to the rear of the turret and gave him a low cupola with a PTC rotating periscope. Other aspects remained the same as on the original T-150 turret. Only a simple sketch of it was done, with a slightly more detailed drawing of the new commander’s position. It was not considered, but it was used as the basis of the Object 222’s turret, which was essentially the T-150 with a completely new turret .
The November 1940 sketch for an improved turret for the T-150.
Source: Warspot New commander’s position on the proposed turret. It was never considered for production but served as the basis for the one on the Object 222.
Source: Warspot
Object 221 – The T-150’s Bigger Brother
As per the request from 17 July, 1940, two tanks were supposed to be built with 90 mm armor, one with a 76 mm gun and one with an 85 mm gun. The first became the T-150, however, the latter had a more troubled development. When researching about the mounting of a 85 mm gun on the chassis of the KV-1, it was realized that it would not fit in the standard KV turret and a larger turret combined with additional armor would require a longer hull. This meant that both the 90 mm and 100 mm variants armed with an 85 mm gun would receive a longer hull, by one roadwheel (a total of seven). The 100 mm armored variant armed with the 85 mm gun became the T-220.
The 90 mm variant was named Object 221 or T-221. It was intended to mount the same turret and 85 mm F-30 gun as the T-220. However, there were serious delays, and the Izhora plant only managed to deliver hull components for the T-221 by 10 February 1941, and the F-30 gun and turret were not ready. On 19 February, Marshall of the Soviet Union G.I. Kulik proposed that the 76 mm F-27 gun be mounted inside a KV-1 turret instead, but nothing was done. The Object 221 remained abandoned until April, when it was used as the basis for the KV-3 (Object 223), though 30 mm of extra frontal armor were required for it to reach the specified armor thickness.
Design
For the most part, the T-150 was identical to the KV-1. As the additional 15 mm of armor were added on the outside of the hull, the internal layout for the crew was unchanged. The main armament was, as requested, a 76.2 mm F-32 gun, coaxially paired with a 7.62 mm DT machine gun to the right of the main gun, with another DT machine gun at the rear of the turret and one in the hull, next to the driver. Both machine guns were mounted in ball mounts.
The weight of the T-150 reached 50.16 tonnes, around 6 tonnes heavier than a KV, and went past the weight threshold by over 2 tonnes. Due to the increased weight, the suspension was reinforced. Otherwise, the hull remained identical to that of the KV-1, with front idler, large rear sprocket and 6 steel-rimmed roadwheels.
The front of the tank had the same features as the KV-1, with 2 tow hooks on the lower plate, a single driver viewport in the center of the upper plate, with a driving light to its right and ball mounted machine gun to its left.
The turret was essentially a KV-1 turret with thicker armor, but certain changes were made to accommodate the commander’s cupola. It was fixed in place and of cast construction. At the front, a fully rotating PTC periscope was mounted, with 6 other triplex periscopes around the cupola. The commander’s cupola likely lacked a service hatch, meaning that the commander and loader would likely have to share a hatch. The turret also featured the standard KV-1 vision devices, a PTC rotating periscope for the gunner and another periscope to the side and 2 facing the rear. Direct vision slits were provided over the machine gun ports. This meant that, on paper, the T-150 offered better vision for the crew than the KV-1. The driver’s vision systems were not changed.
The main novelty of the T-150 was its 90 mm armor all around the turret and hull. The turret deck, hull deck and hull belly were 30-40 mm thick. The commander’s cupola was rather large, but was also 90 mm all around and, thus, was not a weak spot. Frontally, this was a 20% increase in raw thickness over the KV-1 in most areas.
Side view of the T-150. The tarpaulin on the fender was used to cover the turret and gun during trials.
Source: Warspot
Crew
The crew of the T-150 was the same as that on the KV-1, with 5 men: driver, radio operator/bow machine gunner, commander, gunner, and loader.
The commander was seated to the right of the gun, where he would be able to observe the battlefield from his cupola. He was also tasked with loading the coaxial DT machine gun on his side. The gunner sat on the other side of the gun, to the left of the turret. He would aim and fire the gun via a TOD sight. He had a rotating PTC and fixed periscope for external vision. He was able to rotate the turret via an electric system but also with a hand crank. Behind the commander sat the loader, on a removable seat (for easier maintenance/loading). He would load the main gun with shells stored on the side turret walls and in cases on the hull floor. He would also operate the rare turret machine gun, should the situation require.
In the center of the hull sat the driver, and to his left the radio operator, who also manned the bow DT machine gun. The radio was mounted underneath the frontal plate.
Engine and Propulsion
The engine installed on the T-150 (and T-220) was the four-stroke V-5 diesel, 12-cylinder in V-config with an output of 700 hp. It was essentially a boosted V-2K (600 hp), which itself was a boosted variant of the V-2. The main problem was that the V-2K was unreliable and barely guaranteed to work for up to 100 hours. Consequently, the V-5 was even less reliable. So much so that, during trials, the chief designer from Plant No.75 could not guarantee the function of the engines on the T-150 and T-220. Combined with the poor design of the engine’s cooling system done by SKB-2 engineers, the engine would have several major issues during the trials and only worked for 199 km, or 24 hours.
The fuel tank capacity remained the same as on the KV-1, at 615 liters, which reduced the range to 220 km (on roads).
Rear of the T-150 tank.
Source: Warspot
Armament
The main armament on the T-150 was the 76.2 mm F-32 gun. It was developed by Plant No.92 in Gorky in the late 1930s and was tested on the BT-7. It could fire BR-350A and BR-350B (APHE), BR-350SP (AP), and OF-350M (HE). The shell weight varied between 6.2 kg and 6.78 kg, depending on the type. The muzzle velocity was between 613 and 621 m/s (figures vary depending on the source consulted). In January 1941, the KV-1 would enter production with the F-32 gun. It was ballistically very similar to the L-11 it was replacing on the KV-1, while the T-34 would receive the far more potent F-34 76 mm gun the same year.
76 mm F-32 gun, used on the T-150
Source: Sovietarmyforum via Rotor
For proximity and anti-infantry defense, three 7.62 mm DT machine guns were mounted, one coaxially, to the right of the gun, which could be used for ranging closer targets (muzzle velocity around 840 m/s). The front facing machine gun in the bow was for suppression of infantry and the machine gun in the rear of the turret was for defense against flanking infantry.
Trials
On 14 January 1941, the People’s Commissariats of Defence and People’s Commissariats of Heavy Engineering requested that the T-150 and T-220 be tested at the LKZ proving grounds. A commission, headed by the Military Engineer 1st Rank Glukhov and with representatives from the GABTU, would monitor the testing of the tanks. According to the commission for field testing, the following goals were intended.
Determining the tactical and technical characteristics of the tank.
Identifying the shortcomings in the designs and their elimination prior to mass production.
Judging whether it is possible to conduct military tests.
Accumulating data for operating and repairing the tanks.
The T-220 during its trials. It was developed alongside the T-150 from the original request for a KV tank with 100 mm of armor and 85 mm gun.
Source: Tank Archives, colorized by Johannes Dorn
The tests would begin the following day on both tanks. During this time, several issues were quickly identified. On 25 January, the two prototype tanks were weighed, with the T-150 weighing 50,160 kg and the T-220, 62,700 kg. The problem here was that the GABTU specifically requested the T-150 to weigh a maximum of 48 tonnes and the T-220 56 tonnes. A report written by Military Engineer 1st Rank Glukhov on 28 January to the Head of Armored Department of the GABTU, Military Engineer 1st Rank Korobov, in the midst of the trials, showed that the commander’s cupola was poorly made (the observation devices were located too high, vision was inconvenient) and was placed in the loader’s position, who is not in command of the tank. Comically, the Chief Designer of Plant No.75, T. Chuptakhin, who was present at the trials, was not able to guarantee the operation of the engines installed on the T-150 and T-220 tanks. One of Glukhov’s reports included the following passage:
“The T-150 tank, after replacing the engine that failed during the factory run on 21 January, has not yet been brought back to the accepted state required by the Quality Control Department and military representatives.”
The gunshield was crudely made and provides only 3º of gun depression, instead of the 6.5º, as specified by the drawings.”
Due to the breakdown of the experimental V-5 engine provided by Factory No.75, the T-150 traveled only 199 km, or 24 work hours. Several issues were found and once again reported by Glukhov:
“The engine’s oil cooling system prevents the tank from driving at high speeds in the 3rd and 4th gear (at an outside temperature of 9° to 12°, the temperature of the injected engine oil increased rapidly after 5 minutes of motion in 3rd and 4th gears). Normal operation of the engine (inlet oil temp. 70°-80°). Due to the poor design of the cooling system, driving trials on the T-150 would cease.”
The T-150 (left) hooked up to the T-220 (right) during trials.
Source: bronetechnikamira.ru
Instead, focus shifted towards firing trials, especially relevant as the F-32 gun had just replaced the L-11 gun on the KV-1’s production lines. Firing while stationary and firing during short stops went as expected (considering the 4-5 second aiming time), but firing on the move was unsatisfactory, though many of these results were entirely based on circumstances such as terrain and gunner skill, and the gunner conducting the trials, although experienced, was still not entirely familiar with the gun and tank.
Simultaneously, loading times were measured, depending on where the rounds were stowed. When loading shells from the right turret side (9 rounds), 5-7 rounds per minute were sustained. When loading shells from the left side of the turret (9 rounds), the rate of fire dropped to 3 rounds per minute, as the loader had to lean to the other side of the turret. The situation got worse when loading via casings that held 3 rounds. These would have to be lifted up and opened before the shells could be loaded in. This process slowed the rate of fire to 1-2 rounds per minute. In contrast, although not practical, when the shells were simply laid on the floor, 11 rounds per minute could be sustained. Furthermore, the ammunition cases, stowed on the hull floor, would often catch on one another when attempting to lift them, and on 6 separate instances, rounds were jammed inside. The sharp edges of the cases also injured the loader’s hands. Consequently, the commission noted that the ammunition stowage system had to be reworked.
Several issues had been noted with the crew’s positions as well. Firstly, the commander’s seat (combined with the cupola) were criticized for being fixed in place, preventing the commander from viewing out of the periscopes while seated. Likewise, he could not stand, as there was no room, but rather the commander had to stand with his knees slightly bent, in a semi-squatting position (naturally very tiring) to see out of the cupola. Other complaints included that he had to turn very frequently to communicate to the rest of the crew and he was also charged with loading the coaxial DT machine gun.
The gunner’s position also required improvements. The sight was deemed too far forward and slightly to the left, and the seat required more adjustment. The footrests and pedals required work as well. The knee would be bent too much. Additionally, the heel rest was too far down, requiring the gunner to keep his heel in the air in order to maintain his toes on the pedal, or overextend his ankle, both very tedious tasks.
The loader, aside from the aforementioned loading problems, would have his workspace cramped up by the commander’s seat, only 6-8 ammunition cases were easily accessible, and the machine gun drums were in the way when lifting rounds from the left turret wall.
T-150 after trials, February 1941. The background was manually ‘erased’.
Source: Warspot
Testing of the T-150 was concluded on 14 February. The trial results were reported back to the GABTU and People’s Commissariat of Heavy Engineering. Although the aforementioned issues were noted (and such problems were understandable for a prototype vehicle), it was decided to move forwards with the T-150 project, but in an altered form. Based on reports during this time, both the T-150 and T-220 were sometimes called KV-3. The more common use of this name came with the Object 222 and later with the Object 223, the KV-3 commonly known today.
On 21 February, a commission was made for analyzing the reason for the failure of Plant No.75’s engines on both the T-150 and T-220, and estimating a time of arrival of the fixed engines. The deadline was set for 10 April.
During the same period, between 18 and 24 February, Plant No.75 tested the V-5 engine on KV tank U-21, and it broke down once again, after 40 hours of operation.
On 1 March, the T-150 was officially canceled. The V-5 engine was still unrefined, and the tank was deemed to have several issues necessary to fix, but there was no point in doing so. Instead focus was shifted to the Object 222, which was based on the T-150.
Object 222
Many of the issues of the T-150 that were discovered during the factory trials were identified far earlier on. As a result, the SKB-2’s design bureau started work on a new tank in January-February, 1941 to fix these issues. The new tank, which used the same hull as the T-150, would be indexed Object 222. Originally, the differences between it and its predecessor consisted of a new cooling system and a new turret. This new turret was slightly larger, had flat sides (as opposed to 15° angled inwards on the KV-1 and T-150), and a slightly sloped frontal plate. The commander and his cupola were moved to the back of the turret as well.
By the end of February, the People’s Commissariat of Defence and the Central Committee of the Communist Party proposed accepting the KV-3 (Object 222) into service. Additionally, the topic of improving the main armament to the 76.2 mm F-34 was also raised. This gun had improved ballistics over the previous F-32 on the T-150. As for the propulsion, the tank was to use the same V-5 engine.
On 3 March 1941, a commission was formed, consisting of Military Engineers 2nd Rank I.A. Burtsev and I.A. Shpitanov, Military Engineer 3rd Rank Kaulin, LKZ Director I.M. Zaltsman, SKB-2 Director J.Y. Kotin, Director of LKZ 1st Dept. A.Y. Lantsberg, and NII-48 research institute engineers V. Dalle and A.P. Goryachev. Together, they reviewed the drawings and a full-scale wooden mock-up turret of the Object 222 turret mounted on a KV-1 (for simplicity’s sake). Turret armor would have been 90 mm all around and 40 mm on top. Several issues were identified, such as the flat turret walls, which were deemed to decrease protection, the less than ideal commander position, and the lack of hatch on the cupola for the commander. Despite these issues, the commission concluded that the turret should be built anyways, since there was little time to redesign it.
On March 15, the Council of People’s Commissars of the Soviet Union and the Central Committee of the Communist Party gave decree No. 548-232§, which imposed that LKZ had to switch mass production to the KV-3 (Object 222) in June.
The officials were confident that, by then, the new turret could be tested and refined. As for the T-150’s hull, with the new cooling system and properly tuned V-5 engine, it would run smoothly, as it was essentially just an up-armored KV-1 hull.
Object 222 drawings, circa March 1941. The tank was named KV-3 and was supposed to enter service in June, but the situation changed shortly after. It used the hull of the T-150.
Source: Yuri Pasholok
German Heavy Tanks
However, 4 days earlier, on 11 March, the Soviet Intelligence services had just released a report regarding the German Reich’s tank developments. Notes of several heavy tanks were highlighted, notably three new tanks that were under development. One of them was labeled Mark V, was to weigh 36 tonnes, and be armed with a 75 mm gun. The Mark VI was to weigh 45 tonnes and be armed with a 75 mm gun, and, finally, the Mark VII was to weigh 90 tonnes and be armed with a 105 mm. The first 2 tanks can be confidently identified now as the VK.30.01(H) and VK.36.01(H) and early Tiger mentions. But the latter can only be described as some early proposal to what would become the Pz.Kpfw.VII Löwe, which was first mentioned officially in German documents in November 1941.
This new German heavy tank was nearly double in weight of the KV-3 and considerably above the T-220. The 105 mm gun was far more alarming than the 76.2 mm F-34 that the KV-3 (Object 222) was to be equipped with and the 85 mm F-30 on the T-220.
On 21 March, the GABTU requested the urgent development of a new heavy tank from SKB-2 at LKZ, capable of matching the supposed German heavy tanks. It was to weigh up to 72 tonnes, have 130 mm of frontal armor, and be armed with the 107 mm ZiS-6 gun. It was indexed Object 224 / KV-4. On April 7, the GABTU would rework their approach, requesting that the KV-3 be based on the T-220 (Object 220) and armed with a 107 mm ZiS-6 and weigh 68 tonnes. The new KV-3 was indexed Object 223. An even heavier tank was also conceived, the KV-5 (Object 225), with 170 mm of frontal armor and 150 mm of side and rear armor, weighing over 100 tonnes.
The ‘later’ KV-3 (Object 223) with the 107 mm ZiS-6 gun. Development would start in April, based on the Object 221, and would continue until December 1941.
Source: Warspot
After the invasion of the Soviet Union and the Siege of Leningrad in September, much of the SKB-2’s design bureau and its prototype tanks were evacuated to the ChTZ plant in Chelyabinsk, which was now renamed ChKZ, or Tankograd.
Most of the work on the heavy tanks was stopped in order to focus on more sensible topics at ChKZ. The only exception was the Object 222 (which had now been renamed to KV-6) and the Object 223 (KV-3). The GABTU was against the KV-6 and insisted on improving the armor of the T-150 to 120 mm and adding a new ZiS-5 gun. These were the last efforts on these tanks. The Object 223 (KV-3) progressed until December 1941.
These experimental tanks were incredibly expensive. A letter sent on 30 May 1941 to Military Engineer 1st Rank Korobov by A.Y. Lantsberg described the development costs of the major KV series of heavy tanks (Object 150, Object 220, Object 221, Object 212, Object 218, Object 223, Object 224, and Object 225). These had a total development sum of 5,350,000 rubles. The T-150 project would cost in total 1,500,000 rubles. In perspective, a KV-1 in 1941 would cost between 523,000 to 635,000 rubles.
Stage of T-150 Development
Price (thousands of rubles)
Draft drawings
50
Technical drawings
50
Prototype construction and factory trials
900
Proving ground trials
100
Drawing correction after trials
25
Repair of prototypes and improvements
375
Total cost
1500
Source: CAMO RF 38-11355-101
One of the more sensible alternatives was the KV-1E (the E is a post-war addition and derives from the Russian word meaning shield or screens), a regular production KV-1 with 30 mm to 25 mm additional armor plates, making the protection of the KV-1E superior to that of the T-150. The idea of the KV-1 with appliqué armor appeared on 19 June, 1941 and would be given to troops by July.
KV-1 with appliqué armor knocked out. The additional armor on the side of the hull and turret can be seen.
Source: World War photos
Second trials
The work on Object 222, Object 223, Object 224, and Object 225 tanks did not mark the end of the T-150 prototype’s career. During the month of June 1941, the T-150 was retested with a worked-out V-5 engine and improved cooling system. This time, it traveled 2,237 km by 19 June. In total, 5 different V-5 engines had been installed on the tank during its trials. Amongst the issues noted were:
Oil leaks from the gearbox’s primary oil retainer.
Teeth from the 3rd and 4th gear as well as conical gear were sheared off.
Collar bracket of the 2nd and 4th gears were worn out by 4 mm.
2 rubber shock absorbers had been destroyed.
Paper fuel filters failed
Several new production methods had also worked well, such as hot-pressing the torsion bar with the torsion arm together, and the gearbox casing, made out of recycled aluminium, did not show sign of damage or failures after 1671 km.
T-150 in Combat
As the Soviet Union was suffering rapid defeats against the Axis powers, prototype tanks were pressed into service. The T-150 would be no exception. It entered service with the 123rd Tank Brigade on 11 October 1941. A week later, on 18 October, the brigade, part of the 8th Army, fought around Neva Dubrovka and later crossed the Neva river. On 18 May 1943, the T-150, by then part of the 31st Guards Heavy Tank Regiment, was listed as knocked out beyond repair. But the need for tanks was there and it was sent to Plant No.371 for repairs and entered service with the same regiment in July. The commander was Guards Junior Lieutenant I.A. Kuksin and driver-mechanic was Technician-Lieutenant M.I. Shinalsky and the tank received the number 220 and callsign “Som” (Catfish).
Shortly after, Kuksin’s tank would partake in the Mga Offensive or Third Battle of Lake Ladova, and on 22 July 1943, the 31st Guards Heavy Tank Regiment, alongside 63rd Guards Rifle Division, engaged enemy forces south-east of Leningrad. During the fighting between July 22 and August 6, the 31st Guards Heavy Tank Regiment recorded kills of 10 enemy tanks (allegedly 5 Tiger tanks, 3 Panzer IVs, and 2 Panzer IIIs), 10 pillboxes, 34 foxholes, and 750 enemy personnel. Kuksin’s T-150 and his crew also performed well. During this period, they recorded the destruction of 5 foxholes, 2 light machine gun posts destroyed, and 36 soldiers. Their tank was also hit in the track and immobilized, yet the crew managed to get the track together and continue fighting. The tank held its position for 4 days, for which Kuksin and his crew received the Order of the Red Star.
KV-1 with number 207 during maintenance and another KV conducting track repair. According to Yuri Pasholok, these belonged to the 31st Guards Heavy Tank Regiment and the photo was taken in late July 1943. The tank with the track being repaired is claimed to be the T-150 itself.
Source: Warspot
On 12 August, the Regiment was assigned, with the 73rd Marine Rifle brigade, to capture the village of Anenskoye. The 1st and 4th companies attacked on 18 August at 04:55. The companies suffered heavy losses and, by 06:00, 9 out of the 10 tanks were taken out of battle, with only tank 206 being in working order. Amongst these casulties suffered on that day, the T-150 was one of them. Junior Lieutenant I.A. Kuksin, gunner Senior Sergeant A.S. Yurdin, driver Technician-Lieutenant M.I. Shinalsky, and loader Guards Seargant I.M. Brezhak were killed in action on 18 August and the T-150 was sent back to Plant No.371 for repairs.
Commander of the T-150, Junior Lieutenant I.A. Kuksin (left) and Guards Seargant I.M. Brezhak (right).
Source: Yuri Pasholok
Alternatively, a document dated 18 November 1943 shows that a new driver was assigned to the T-150 (noted as KV No.T-150, raising the question as to if the T-150 was ever given number “220”), and was still commanded by Kuksin.
It is worth highlighting that the T-220 also saw combat service, but its new turret and 85 mm F-30 gun were replaced with a regular KV-1 turret. The tank was knocked out during the defense of Leningrad.
Conclusion
The T-150 (KV-150 / Object 150) was, on paper, a minor upgrade to the KV-1, with just 15 mm of additional frontal armor, a more powerful 700 hp engine, and a new commander’s cupola. While the implementation of these changes proved problematic at first, the T-150 proved to be a very important step towards the design of even larger and heavier KV tanks. These ultimately proved to be a waste of money, time, and resources, assets which the Soviet tank industry did not have, especially with the Axis invasion. Like many Soviet pre-war prototypes and its larger brother, the T-220, the T-150 prototype saw combat service well into 1943, but what happened after is unknown.
T-150. Illustration by Pavel Alexe.Object 222. Illustration by Pavel Alexe.
T-150 / KV-150 / Object 150 Specifications
Dimensions (L-W-H) (approx.)
6.76 x 3.33 x 3.01 m
Total weight, battle-ready
50.16 tonnes
Crew
5 (Commander, gunner, loader, driver, radio operator)
Propulsion
V-5 12-cylinder diesel, outputting 700 hp.
Speed
35 km/h
Suspension
Torsion bar, 6
Armament
76.2 mm F-32
3x 7.62 mm DT machine guns
Armor
Front/sides/rear of hull and turret: 90 mm
Top/Belly: 30 to 40 mm
Marishkin's KV-4 design. Illustration by Pavel Alexe.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
The KV-4 program was started in March 1941 to deal with alleged new heavy tank advances by the German Reich. Development took place at the Leningrad Kirov Factory design bureau SKB-2 headed by J.Y. Kotin. A design competition was held, with over 27 different design proposals. While many designs were appreciated for their innovative features, even more were disregarded. One of these was proposed by engineer F.A. Marishkin, who’s design featured a large complex turret and an unremarkable hull.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
With the expansion of German aggression over Europe in 1940, Soviet leadership followed events with unease, despite their non-aggression pact with the German Reich, signed in August 1939. Their successful use of tanks was unprecedented and other nations rushed to expand their tank development and armament programs. During this time, the Soviets would start fielding the KV-1 heavy tank, based on experiences from the Winter War. However, it would quickly become apparent that it was rushed due to Stalin’s requests and still needed plenty of fine tuning. By the start of Operation Barbarossa, the KV-1 would still prove a lethal weapon, with excellent protection and adequate firepower, but was let down by significant quality, logistical and training problems.
On 11 March 1941, the Soviet Intelligence services submitted a report to the GABTU (Main Directorate of Armored Forces) regarding the development of German tanks. Most noticeable was the section on heavy tanks, where, amongst others developments akin to the VK.30.01(H) and VK.36.01(H), was the mention of a 90 tonne Mark VII tank, armed with a 105 mm gun, which is know now was some early variant of the later Pz.Kpfw.VII Löwe. This came as an unpleasant surprise to Soviet officials, who only had the aforementioned KV-1 and the hopelessly obsolete T-35 tank. The most advanced heavy tanks in development were the KV-150 (T-150), an improvement based on the KV-1 with 90 mm of frontal turret armor and total weight of 50 tonnes, and the KV-220, armed with an 85 mm F-30 gun, 100 mm of armor all-round, and total weight of over 60 tonnes. While both were very respectable on paper and superior to all German tanks of the time, they had reliability issues, with the KV-220 breaking two engines while testing, though the engine was equally unreliable and only two were built.
Thus, the GABTU set out to develop a new heavy tank to match the German tanks. On 21 March, they laid out all the requirements for the new heavy tank. It was to be armed with the new 107 mm ZiS-6 developed at Factory No.92 by V.G. Grabin. The armor was to be 130 mm to 120 mm all-round and a weight between 70 to 72 tonnes. Propulsion was set to be the M-40 diesel aviation engine with 4 TK-88 turbochargers. The tank was to be equipped with a vast array of secondary weapons as well, namely a 45 mm gun and at least three 7.62 mm machine guns, as well as a flamethrower.
Development of the KV-4 would take place at the LKZ (Kirov Leningrad Factory) SKB-2 design bureau, the same office responsible for all the previous KV tanks. Production of the first prototype was assigned to the Izhora plant, based on LKZ drawings. Thus, the tank was named KV-4 and received index Object 224. The project deadline was set to 17 July for the drawings and October for first prototype production.
Shortly after the initial release of the requirements, the GABTU edited their request, specifically on 7 April. Firstly, they would request a heavy upgrade of the KV-220, named KV-3, that would act as a stopgap until the heavier tanks were ready, armed with a 107 mm gun and 120 mm of frontal armor. Likewise, an even heavier tank was requested, named KV-5, with frontal armor thickness of 170 mm and side of 150 mm, and weight of at least 90 tonnes, also armed with the 107 mm ZiS-6. To better fit the KV-4 between the two new vehicles, its weight threshold was lifted to at least 75 tonnes, and 125 mm of armor at the sides. To increase the urgency of the matter, the deadline was tightened to 15 June.
Over at SKB-2 design bureau, which was headed by J.Y. Kotin, work would set on developing all 3 tanks. Interestingly, as a result of the loose requirements set by the military, Kotin would challenge his engineers to a design competition, in an attempt to bring out the most innovative ideas. With the approval of the factory director, I.M. Saltzman, Kotin was given the necessary funds to award the top designers with significant financial awards. Over 24 designers entered the competition, with just as many different concepts submitted. On the 9 May, the winners were announced, in first place being N.L. Dukhov, a trio of designers, K.I. Kuzmin, P.S. Tarapatin and V. I. Tarotko in second place and N.V. Tseits on third. In total, 11 designs and 13 engineers were awarded.
However after the competition was over, work on the KV-4 severely stagnated, to the point where Marshal of the Soviet Union G.I. Kulik had to personally come over and attempt to speed up the process, to no avail. Truth is, most of the efforts went to the KV-5, based on knowledge from the KV-4. Even so, the KV-5 was in a very early stage when the German Reich began their invasion of the Soviet Union, on 22 June 1941, and their quick advance into Soviet territory would put great strain on tank factories.
By September, the German forces were advancing towards Leningrad, and the SKB-2 design bureau was evacuated to ChTZ (Chelyabinsk Tractor Plant), which was renamed ChKZ (Chelyabinsk Kirov Plant), or as more commonly known, Tankograd. Unfortunately for the heavy KV designs, they were seen as a massive resource drain and work on them did not recommence.
F.A. Marishkin
Alongside 5 other engineers, F.A. Marishkin was head of the design of the transmission of the KV-1 while also being part of the design team of the SMK and T-150. After the war, he would continue working at the Kirov plant as one of the designers of the KT-12 forestry tractor, but also on the development stages of the T-10.
F.A. Marishkin after the war Source: Constructor of Combat Vehicles
Design
Compared to the majority of the KV-4 designs presented, Marishkin’s can be seen as one of the more conservative ones in regards to general layout and design. What was essentially an enlarged KV-220 hull was mated to a very large main turret, with a secondary turret on top. The front of the hull was a ‘stepped’ design, consisting of a large lower plate, a steeply angled ‘hood’ followed by a flatter but thickened section in the armor connecting to the hull roof. The side armor was simply flat all along. The rear was very similar to the KV-1, consisting of two plates with a gap in between for engine cooling airflow. The main turret was mounted between the second and sixth roadwheels. Frontally, it consisted of a single plate stamped into a curved shape. The sides of the turret are not specifically drawn out on the blueprints, but they curved inwards at the rear, as well as being angled upwards for improved protection.
Perhaps the only unusual aspect of Marishkin’s design was the secondary turret, specifically its placement. It was towards the rear of the turret and offset to the right. As the main turret was curved and angled inwards, the secondary turret hung over the main turret walls, requiring a form of extension of the turret walls to support the turret ring. This certainly complicated the construction process.
Side cutout view of the KV-4 proposed by Marishkin. Source: ASKM
The recoil distance of the ZiS-6 107 mm gun was not specified, but it is clear that, if the secondary turret was placed centrally, the gun recoil would slice the secondary turret gunner’s legs off (see KV-4 Kruchenykh). The only other option would have been extending the turret’s bustle size, but that might have not been possible considering balance and the limited turret ring size.
Top view of the hull, showing the different fuel tanks on the sidewalls and floor, engine, and final drive. Of significant interest are the two circles in the center, the big one representing the main turret ring, and the smaller one, the secondary turret. Source: ASKM
The engine used was a M-40 1,200 hp engine, originating from an aviation engine and capable of running on both diesel and kerosene. It had a V12 configuration, 61.07 liters displacement, and featured 4 TK-88 turbochargers. Fuel tanks were fitted alongside the hull sides and floor, underneath the turret.
Side cutout view of the hull layout, with a cross section of the M-40 engine and fuel tanks. The armor is not shown. Source: ASKM
The suspension was a standard KV series layout, with 8 steel-rimmed roadwheels sprung by torsion bars and with travel stops. The drive sprocket was at the back, connected to the brakes and final drive ensemble.
Crew
The crew on Marishkin’s proposal was 7, one more than the GABTU-specified 6. The exact layout and positions are unknown, but based on the tank layout and similar designs, the following can be concluded. The crew consisted of the driver, radio operator, main gunner, 2 main gun loaders, commander (which was also the secondary armament gunner), and secondary loader.
The driver would be seated (as seen in the drawing above) in the front of the hull. Next to him would be the operator of the 10-R tank radio.
The remaining 5 crewmembers would be seated in the turret. The main gunner was seated to the left of the gun, with a loader behind him. The other main loader was likely on the opposite side, to the right of the gun breech. The commander was seated to the left of the 45 mm secondary gun and the loader to the right.
This layout is purely speculation by the author, largely based on space, practicality, and other KV-4 designs with known crew positions. It could be argued that certain positions did not exist or should be rearranged, for example, the second main loader replaced with the tank commander and the secondary gun to receive its own designated gunner.
Armor
Like most of the pre-war Soviet heavy tanks, the armored plates were simply welded together without interlocking. A likely form of connection for the heavier plates was via pins, like on the German Maus tank. These would physically improve the connection between plates but could prove to further complicate the manufacturing process and cause weakening of the armor in those areas to be more susceptible to cracking and shattering.
The lower frontal plate was 130 mm thick, pressed into shape. The upper part of the armor consisted of a single plate, with the bottom being 80 mm thick and the top part 130 mm, pressed to form a steep hood and driver’s front plate. The side was a single flat 120 mm thick plate. The turret consisted of a single frontal plate, 130 mm thick, pressed into shape. The side armor is more speculative due to the lack of drawings, but would also have followed a similar process, albeit with a 125 mm thick plate.
Armament
The main weapon used on all KV-4 designs was the 107 mm ZiS-6 developed a few months earlier by Factory No.92 by V.G. Grabin by own initiative. With 800 to 840 m/s muzzle velocity and a 18.8 kg shell, it was a very potent anti-tank weapon, capable of penetrating 115 mm of armor at 1,000 m. The gun was tested in June and July on a KV-2 testbed and would enter production a few months later. However due to the KV-4 and subsequently KV-3 and KV-5 tanks never being built, the half-built guns had to be melted and recycled.
Secondary armament consisted of the 45 mm 20-K gun, used on the majority of Soviet light tanks at the time, as well as at least two 7.62 DT machine guns.
The KV-2 testbed with the 107 mm ZiS-6 gun, June 1941. Source: Warspot
Death of LKZ’s Heavy Tanks
The Axis forces made quick progress into Soviet territory and by August were already approaching the city of Leningrad. To avoid capture and disruption of developments, many of the engineers of the SKB-2 design bureau were relocated to the Chelyabinsk Tractor Plant (ChTZ), which was renamed to Chelyabinsk Kirov Plant (ChKZ) upon their arrival. However, it was clear that the heavy tank developments in the form of the KV-3, KV-4, and KV-5 were more resource and financial pits for the Soviet defense than any actual help. The projects were all abandoned and development switched to improving the KV-1, which resulted in new successful vehicles, such as the KV-1S.
Conclusion
While, with hindsight, the entire KV-4 program ended up being a massive waste of resources, it is clear that some designs were fundamentally better than others, like the winning design by N.L. Dukhov. In contrast, the design by Marishkin was not particularly original and was not deemed as effective considering the liberal requirements and effective armament. Even today, his design is one of the lesser known and least appreciated designs from the program.
Marishkin’s KV-4 design. Illustration by Pavel Alexe.
KV-4 (Object 223) Marishkin specifications
Dimensions (L-W-H)
8.7 – 3.8 – 3.5 m
Total Weight, Battle Ready
86.4 tonnes
Crew
7
Propulsion
1,200 hp diesel V-12 M-40 with 4 turbochargers
Speed
40 km/h (hypothetical)
Armament
107 mm ZiS-6
45 mm 20-K
>2 DT 7.62 machine guns
Armor
Turret: 130 mm
Frontal upper hull: 80 mm
Frontal lower hull: 130 mm
Side hull: 125 mm
Rear hull: 125 mm
Top: 40-50 mm
Belly:40-50 mm
Total Production
0; blueprints only
Sources:
Breakthrough tank KV – Maxim Kolomiets
Stalin’s Supertanks IS-7 – Maxim Kolomiets
KV 163 1939-1941 – Maxim Kolomiets
Confrontation – Ibragimov Danyial Sabirovich
Constructor of Combat Vehicles – N.Popov
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) M. Svirin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
German Lion | Warspot.ru – Yuri Pasholok
Крупный калибр для крупных КВ | Юрий Пашолок | Дзен (dzen.ru) – Yuri Pasholok
Tank building on the verge of common sense | Warspot.ru – Yuri Pasholok
Large caliber for large HF | Yuriy Pasholok | Yandex Zen – Yuri Pasholok
Tank Archives: Soviet 107 mm Guns – Peter Samsonov
Tank Archives: KV-3 Mulligan – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: ZIS-6 Characteristics – Peter Samsonov
Marishkin F.A. (famhist.ru)
KV-4 as designed by Sychev. illustration by Pavel Alexe, funded through our Patreon campaign.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
A few months before the German invasion of the USSR, the Soviets were working on developing massive heavy tanks. One of these programs was the KV-4 projects, which included 27 different proposals. One of these was from LKZ engineer L.E. Sychev. Instead of focusing on revolutionary and unique features, he built upon and perfected the concept already tested on the SMK heavy tank. These efforts placed his design in 4th place in the KV-4 design competition.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–
In March 1941, the Soviet Intelligence services sent a letter to the Soviet Main Directorate of Armed Forces (GABTU) discussing the development of German tanks. Here, a 90 tonne heavy tank was described, armed with a 105 mm gun. Yet, only by November 1941, the first mentions of a tank fitting this description appeared, the Pz.Kpfw. VII, or Löwe. Understanding how far behind their heavy tank development was, the Soviets set about the urgent development of a new heavy tank.
Development of the new beast became the responsibility of the Kirov Leningrad Plant (LKZ) and its SKB-2 design bureau. The bureau had already designed the only somewhat capable heavy tank in service, the KV-1, however, it proved to be unreliable, slow, and heavy once war commenced. Up until that point, LKZ had also designed several heavy tanks in parallel with the KV-1 or as a direct development from it, such as the T-150, KV-220, and KV-3. With hindsight, the KV-220 was a genuinely capable design, comparable to the later German Tiger I heavy tank. It weighed 62.7 tonnes and was armed with an 85 mm F-30 gun. On the other hand, during trials, it was cumbersome and unreliable, breaking 2 engines.
The new heavy tank to be designed by LKZ was given the designation KV-4 or Object 224. Just 10 days after the original letter was sent, on 21 March, the GABTU had released the specifications for the technical capabilities of the tank. It was to be a 70-tonne tank, armed with the 107 mm ZiS-6 gun in, a 45 mm Model 1937 or 1938 as a secondary gun, 3 DT 7.62 machine guns, and a flamethrower. Armor was to be 130 mm at the front and 120 mm at the sides. Propulsion was provided by a massive 12 cylinder M-40 engine with 4 TK-88 turbochargers, outputting 1,200 hp with a displacement of 61 liters. The crew was to be of 6. Just 6 days later, the project deadline was set to 17 July. Subsequently, based on the LKZ blueprints, Plant No.92 was to build the guns by 1 September and the Izhora plant was to finish the turret and hull by 1 October.
Just 17 days later, on 7 April, the GABTU requested the KV-4 specifications be increased to 75 tonnes weight and armor improvements to 125 mm at the sides and rear. The deadline was also tightened to 15 June. In the same letter, the GABTU requested an even heavier vehicle, the KV-5, with 170 mm at the front and 150 mm at the rear, and weight of 90 tonnes. The sudden changes in design, and the increased time pressure, combined with Stalin’s personal involvement in the heavy tank projects would hurry up the design process. Lastly, the previously designed KV-3 would receive improved parameters, up to 68 tonnes and arming it with the same ZiS-6 107 mm gun as on the heavier tanks, with the purpose of acting as a stopgap tank.
Due to the urgent nature of the project, LKZ began work on the heavy tanks on 10 April. The SKB-2 design bureau headed by J.Y. Kotin was put in charge of their development. Yet instead of pursuing a traditional development path, Kotin, with the approval and funds allocation from factory director I.M. Zaltsman, would set up a design competition for the KV-4. The idea behind this was to gather as diverse and revolutionary design elements as possible. To further encourage this, the competition results would be ranked and the top places awarded financial rewards. By 9 May, the competition was over and over 27 designs were presented by the SKB-2 bureau. First place was awarded to N.L. Dukhov, who designed an enlarged KV-220 with an automated loader aiding system. He received 3,000 rubles. To put this in context, a frontline soldier received 500 rubles for destroying an enemy tank. Second place went to a trio of engineers, K.I. Kuzmin, P.S. Tarapatin and V.I. Tarotko, who together designed a variant with a sponson mounted main gun and secondary gun mounted in a small turret on top. They were awarded 3,000 rubles to split, however their design would be disqualified later because the main gun had limited traverse. Third place went to senior engineer N.V. Tseits, who designed a tank with a very low hull at the expense of a very large turret. He received 2,800 rubles. Due to the disqualification of the second place contender, Tseits’ design would later be selected as the basis for the KV-5. In total, 11 designs were awarded funds. The design by L.E. Sychev was appreciated due to the well-thought-out layout and origins from a trialed tank, the SMK. Thus he was given 4th place in the competition and awarded with 2,000 rubles.
The SMK multi-turreted tank, likely a source for Sychev’s KV-4. Source: Drikus club
L.E. Sychev
Born in 1913 in, what was at the time St. Petersburg, Leonid Efimovich Sychev undertook his bachelors project at the SKB-2 design bureau at LKZ while studying at the Leningrad Polytechnic Institute in 1932. Just 2 years later, he graduated, and in 1935, started work at SKB-2. He worked on the T-28 and later SMK. As for the KV-1, he first refined the torsion bar suspension alongside N.V. Tseits and G.A. Seregin. Later, he was appointed chief designer for the KV-1 and became the SKB-2’s chief designer of armament in 1940. He was chief designer of the KV-220 and initially, he was also to be chief designer for the KV-3, but was replaced by B. P. Pavlov. After the outbreak of the war, he also worked on improving the T-34, alongside A.A. Morozov. He was awarded the Order of the Red Star, among many others.
Leonid Efimovich Sychev likely after the war. Source: Museum of SPbPU
Design
As with a handful of other KV-4 designs, Sychev heavily inspired his tank layout upon that of the SMK heavy tank, designed by the same bureau just a few years prior. It featured a long hull, with a steeply angled frontal armor plate. Likewise, the engine was mounted in an upwards rising deck plate. Like on the previous SMK and T-100, a smaller turret armed with the 20-K 45 mm gun was mounted towards the front of the hull and slightly offset to the right, while a larger turret, armed with the 107 ZiS-6 gun was mounted centrally. On top of the main turret was an additional fully rotating commander cupola, armed with a 7.62 DT machine gun. An additional DT machine gun was mounted coaxially in the secondary turret.
As required by the state, the KV-4 featured a 1,200 hp V-2SN diesel engine with 4 turbochargers. According to Sychev, it was enough to allow the 95 to 100 tonne tank to reach top speeds between 40 and 45 km/h, though that is extremely optimistic. The entire powerpack ensemble was situated in the rear and featured an ingenious air intake and cooling system, using overlapping armor plates to prevent entry of shrapnel and debris. The fuel tanks were positioned in the sides of the hull.
Side cutout view of Sychev’s KV-4 proposal. Note the steeply angled frontal hull. Source: ASKMPartial top view of Sychev’s KV-4. While the drawing provides excellent view and understanding of the hull, the turrets only have their outlines drawn in. Source: ASKM
Crew
Similarly to the SMK, Sychev’s KV-4 had a crew of 8: commander, main gunner, main loader, turret mechanic/loader assistant, driver, radio operator, secondary gunner, and secondary loader. To further complicate the topic, the exact positions and roles of the crew were never specified or detailed. This leaves a lot of room for interpretation and guesswork based on other KV-4 designs and previous similar tanks, such as the SMK and T-100.
The main turret housed 4 crew members. The main gunner sat to the left of the main gun, and used his main gun sight for vision, though it is likely he would have received his own periscope. The exact position of the tank commander is unknown, though he would have sat on either side of the gun. His head would be inside the main rotating cupola, giving him a commanding view of the battlefield (at 4 m), as well as the ability to independently engage infantry and suppressive fire. The main gun loader would have stood on one side of the gun. He only had 4 rounds in the turret bustle before he would require assistance from the additional loader, standing underneath the turret ring, feeding him shells stowed in the hull.
Towards the bow of the hull sat the driver, to the left side of the hull. Stored to his right was the 20-K 45 mm secondary gun ammunition. Right behind him was the 10-R radio and the radio operator, whose round seat can be seen in the blueprint. The secondary gunner and loader sat in the additional turret, though they were able to have direct communication with both the driver and radio operator.
Armor
All KV-4 designs had more or less the same armor thicknesses all around, i.e. 130 mm at the front and 125 mm at the side and rear. Nonetheless, the layout and angling of these plates varied widely. Unlike previous LKZ heavy tank designs, Sychev used a single sloped plate for the upper hull and the hull extension on which the main turret was placed. This would present a very well armored silhouette from the front. Only the frontal sections of the 2 turrets could be considered weak points. To decrease the effect of this, the front of the turret was rounded, while the entire turret resembled a horseshoe from the top, which made the weaker frontal plate as small as possible, similar to the later German Tiger I heavy tank.
While certainly ingenious, such use of thick armored plates would require intensive steel rolling and bending methods, which the Soviet industry lacked. This was a concern for almost all KV-4 designs, which featured various complex shapes. This issue would be fixed later in the war, with complex casting methods, though a new series of problems would be introduced, such as brittleness and porous steel.
The small commander’s cupola was not necessarily a weak spot in the overall tank’s armor, as it had around 100 mm of armor all around. When in use, only the head of the operator would be inside of it. The machine gun and turret were operated via mechanical controls that were lowered down to chest level.
Armament
Regarding the armament, the main gun used on all KV-4 designs was the 107 mm ZiS-6, developed earlier that year at Factory No.92 under the name F-42. Its designer was the famous Soviet gun designer, V.G.Grabin. It was to be mounted on the KV-3, KV-4, and KV-5 heavy tanks. During summer 1941, the gun was tested on a modified KV-2, with the KV-3 gun mantlet. It had a muzzle velocity of 800 to 880 m/s, shell weight of 18.8 kg, and could penetrate 115 mm of armor at 1,000 m.
The secondary armament on Sychev’s KV-4 consisted of a 45 mm 20-K gun, which was the main gun in service on Soviet tanks at the time. It was mounted in an independent turret, allowing it to engage infantry or lighter armored AFVs independently of the main turret. Moreover, two 7.62 mm DT machine guns were mounted, one coaxially with the 45 mm gun and one in the small cupola on top of the main turret.
KV-2 armed with a 107 mm ZiS-6 during firing trials, June 1941. The man in white uniform was V.G. Grabin himself. Source: State Archives
Conclusion
Sychev’s KV-4 design had impressed Kotin and Zaltsman, was given 4th place in the competition, and he was awarded 2,000 Rubles. The tank featured 2 roomy turrets, well spaced from each other, offering great firing angles and fire coverage. The solutions regarding the engine cooling system and layout were inspired from the SMK and were deemed as effective. Lastly, the flat and steeply armored upper frontal plate ensured excellent protection, especially compared to the designs that opted for a “stepped” layout, like on the KV-1. Despite the large sums of money poured into the project, as well as almost an entire design bureau focusing on it, the KV-4s development stagnated after the competition results were announced. Instead, based on these results, the KV-5 began being developed. The final nail in the coffin for all the LKZ’s heavy tanks was the German invasion of the USSR, and, subsequently, their fast approach towards the city of Leningrad. Consequently, the entire SKB-2 design bureau was evacuated to the ChTZ factory in Chelyabinsk. Here, the wild dreams of heavy tanks were left behind and focus shifted on more down-to-earth solutions.
KV-4 as designed by Sychev. illustration by Pavel Alexe, funded through our Patreon campaign.
KV-4 Sychev specifications
Dimensions (L-W-H)
9.23 – 3.40 – 4 m
Total Weight, Battle Ready
95 – 100 tonnes
Crew
8 (commander, main gunner, main loader, turret mechanic/loader assistant, driver, radio operator, secondary gunner, secondary loader)
Propulsion
1,200 hp diesel V-12 M-40 with 4 TK-88 turbochargers
Speed
40 – 45 km/h (hypothetical)
Armament
107 mm ZiS-6 (F-42)
45 mm 20-K
2x DT 7.62 mm machine guns
Armor
Turret: 135-125 mm
Hull: 130 mm front, 125 mm sides and rear
Top and belly: 40 mm
KV-4 as designed by G. Kruchyonyh, which was the heaviest design of them all, at 107 tonnes.
Soviet Union (1941)
Super Heavy Tank – Blueprints Only
A few months prior to the German invasion of the USSR in 1941, the Soviets started a heavy tank program based on rumors of German heavy tank developments. One of the outcomes was the KV-4 competition, which involved 27 different tank proposals. The heaviest of them all, designed by G.V. Kruchyonyh, would have weighed 107 tonnes, but the design was not successful.
Development
–Dear reader: A more detailed development analysis of the KV-4 program can be found in the KV-4 Dukhov article–-
By 1941, the Soviet Union had experimented with several types of heavy tanks, from some very extravagant super heavy tanks, such as the Grotte proposals and T-42, to more “sensible” designs, such as the KV-1 and its later development, the KV-220. Yet, when the Soviet intelligence services sent a report about the development of German tanks in March 1941, the GABTU (Main Directorate of Armed Forces) was caught off-guard. The report mentioned, among others, the development of a 90-tonne heavy tank armed with a 105 mm gun.
At the time, the USSR’s main heavy tank force consisted of the hopelessly obsolete T-35 and the mechanically unreliable KV-1, which was pressed into service prematurely. Their most capable vehicle was the aforementioned KV-220, which weighed 67 tonnes, had 100 mm of armor and an 85 mm F-30 gun. While this was by no means an inadequate tank on paper, in practice, the testing of the vehicle was going slowly due to a wide variety of issues, such as the unreliability of the engine and various mechanical breakdowns. By the end of the program, only 2 prototypes were built.
Thus, the GABTU began the urgent development of a new heavy tank, and on 21 March 1941, they requested that a new 70-tonne tank be designed and developed to face this new German threat. It was to be armed with the new 107 mm ZiS-6 as well as a 45 mm gun and 3 machine guns. The engine was to be the M-40 1,200 hp V-12, with 4 TK-88 turbochargers. Armor was 130 mm at the front and 120 mm at the sides. The SKB-2 design bureau at the Kirov Leningrad Plant (LKZ) was tasked with its development and thus was named KV-4, with the GABTU index Object 224. This design bureau had plenty of experience in designing heavy tanks, having already designed tanks such as the SMK, KV-1, T-150, KV-220, and KV-3. As part of this, SKB-2 was ordered to have blueprints ready by 17 July 1942.
However, on 7 April, the requirements were once again changed. The KV-3 was to be revived, and its specifications vastly improved. In turn, the KV-4’s weight would be increased to 75 tonnes, and have its armor increased to 125 mm at the sides and rear. The deadline was also brought forward to 15 June. Most interestingly, LKZ was also assigned the development of the KV-5, a 90 tonne tank, with 150 to 170 mm of armor but also armed with the 107 mm ZiS-6. It would compete against the KV-4, with trials expected to be held in the beginning of 1942. In the meantime, until either entered mass production, the KV-3 would act as a stopgap.
The head of the project was J.Y. Kotin, who was also the head of the design bureaus at LKZ. However, instead of giving direct design orders, he took advantage of the loose requirements and set off to test his engineers. Thus, with the approval and budget from factory director I.M. Saltzman, he forged a competition for the KV-4’s development. The idea was that the engineers from the SKB-2 design bureau would compete against each other, with the top 7 places receiving financial rewards.
The results of the competition were announced on 9 May, with 13 designers receiving awards (7 total places, with some designs receiving the same spot). First place went to N.L. Dukhov’s design, which was considered the most sensible alternative, essentially just an enlarged KV-220. He received 5,000 rubles. Second place went to the Kuzmin, Tarotko, and Tarapantin, a trio of designers who worked together. They received 3,000 rubles to split. Their design had the main gun mounted in the hull, with a small turret over the fighting compartment. Third place went to N.V. Tseits, who designed a tank with a very low hull but massive cylindrical turret. He received 2,800 rubles. Fourth place was given to 2 designs. The first was by L.E. Sychev, who designed an enlarged SMK/style vehicle with a steeply angled frontal place, receiving 2000 rubles. Second 4th place was given to A.S. Yermolaev (also awarded 2000 rubles) who designed two standard layout tanks, with the only difference being the addition of a secondary turret on one of them. N.F. Shasmurin received 5th place with one of the more unique designs, mounting the main gun inside a casemate and a KV-1 turret on top. On 6th place, two more designers were awarded the same place. One of the was by K.I. Buganov, with a compact hull and rear mounted stacked turrets. The other was by N.G. Moskvin, which also proposed a standard layout tank with stacked turrets. Both designers were awarded 1000 rubles. Lastly, 6th place was given to 3 designs, with one by L.N. Pereverzev, which featured exposed tracks, similar to early Churchill tank designs. Another 6th place was awarded to Bykov, which was inspired from the SMK layout. Another designer, Kalivod, was also given 6th place but we do not yet know how his design looked like. The remaining designs did not receive any awards. Amongst them was that by G.V. Kruchyonyh, who designed the heaviest competitor, a 107 tonne tank.
As a peculiar side note, allegedly the blueprints of Kruchyonyh’s designed had been misslabeled by N.F. Shashmurin as the KV-5, to show the poor design of the KV-5. This claim was made by historian Yuri Pasholok.
G.V. Kruchyonyh
Georgy Vasilyevich Kruchyonyh was one of the oldest and most experienced tank designers at the SKB-2 design bureau in Leningrad, having worked on Soviet tanks since the 1920s at the Leningrad No.100 experimental tank building factory. During the 1930s, he worked on the T-28, SMK, and KV-1 at the renamed LKZ, and, after the factory’s transfer to ChTZ (later ChKZ), he would work on the KV-13, IS, and various tank vision devices. Yet, one of his most influential works was his marvelous design for the turret for the Kirovets-1, later IS-3. He retired from ChKZ in 1957, having received throughout his career the Stalin Prize, Order of the Great Patriotic War, and the Badge of Honor.
Georgy Vasilyevich Kruchyonyh with his awards. He was a photography enthusiast. Source: Constructor of Combat Vehicles
Design
During the 1930s and 1940s, when multi-turreted tanks were a common theme, two main solutions were used when 2 turrets of different sizes were involved. One was to mount the turrets in a “battleship style” configuration, where the smaller turret would be mounted at the front, while the larger one was pushed behind it. This was by far the most common solution, and had the main advantage of a lower silhouette and presented a smaller frontal target. This would automatically require a much longer hull, as well as decreasing the firing arc of the frontal turret. To fix this, the secondary turret could be mounted on top of the main turret, allowing for a 360° firing angle for both turrets, independent of one another, at the cost of a much taller tank profile and larger main turret.
Side cutout view of Kruchyonyh’s KV-4 proposal. The complex turret layout can be seen. Source: ASKM
Kruchyonyh went with the second option. He would have the secondary turret, which was a simple cylindrical shape on top of the main turret. He would take this concept to the extreme, giving the commander, seated in the secondary turret, his own fully rotating cupola, armed with a DT machine gun, effectively having 3 turrets stacked on top of each other. Another such armed cupola was also placed on the frontal engine deck, for the bow gunner, as opposed to a ball-mounted machine gun in the hull. Despite this, the total height of the tank was 3.78 m, which was still lower than other KV-4 designs, namely the designs by Pereverzev and Shashmurin.
A problem created by placing the secondary turret centrally over the main turret is main gun recoil. From the drawings, it is clear that the gunner of the secondary 45 mm gun would have to be very careful with the position of his right leg. If the seats were attached to the secondary turret and offered independent rotation from the main turret, he and the other crewmen operating the secondary turret would be in the direct path of the main gun recoil, essentially rendering only 1 of the guns operational at the time. The more sensible option is to have the seats fixed into the main turret, however this would mean that the crewmen had to individually rotate themselves to keep in-line with the secondary turret.
The front of the hull was made from a single, curved plate, 130 mm thick. This offered maximal protection without several interlocking plates. The engine was right between the driver and main fighting compartment, with firewalls on either side. The ammunition for the main gun was stowed horizontally in the hull. Behind it was the fuel tanks, engine cooling, and air intake systems.
Top view of the tank, with cutouts for the 3 turrets. Note the rounded rear section of the main turret. Source: ASKM
Crew
Though the GABTU specifications would request a crew of around 6 men, Kruchyonyh would design a tank with a crew of 9, which was likely the reason for why his design was not awarded anything in the competition.
The exact crew positions are not specified, but analysis of the blueprints suggests the following crew setup: tank commander, main gunner, 2 main loaders, secondary gunner, secondary loader, radio operator, driver, and bow machine gunner.
The driver sat at the front of the hull, on the left side. The bow machine gunner operated the small machine gun cupola on the engine deck. Only his head would fit in it, so the cupola and machine gun were operated via mechanical controls lower down.
The gunner, who had to be seated further away from the normal position due to the limitations of the turret ring and the need to push the gun forwards for space for the extra turret, was placed in the main turret. As a result, the gunner’s controls, including sight, had to be moved and angled. One of the main loaders was seated to the left of the main gun, with the other loader was likely in the hull, lifting shells from within it.
The 45 mm gun’s gunner and loader were positioned on the left and right side of the secondary turret respectively. The commander was seated behind the secondary gunner, in an elevated position and used the rotating cupola for a towering overview of the battlefield.
Armor
At 107 tonnes, one would expect that the armor would exceed its peer KV-4 designs. But that was not the case. It had 130 mm at the frontal plates and 125 mm at the sides and rear, just like most other designs. The dimensions were not drastically larger than other designs, with several KV-4s being both taller and longer. This could be attributed to many designers underestimating the final mass of their tanks, while Kruchyonyh was more accurate or was too pessimistic. In contrast, the lightest design was the winning one by Dukhov, weighing 82.5 tonnes, resulting in a 24.5 tonne weight span between the designs.
Armament
As required by the GABTU, the tank was armed with the 107 mm ZiS-6 gun, designed by legendary gun designer V.G. Grabin at Factory No.92, under the name F-42. It was tested on a modified KV-2 in summer 1941 and meant for the KV-3, KV-4, and KV-5 tanks. Production began shortly after, but only when it became clear that LKZ and subsequently Izhora factory could not deliver the tanks in time, the guns were melted, as there was nothing to mount them to. This deeply saddened and angered Grabin, who found it appalling that such powerful and functional guns were being destroyed at a time when any weapon was needed to fight the Germans.
The secondary armament was a 45 mm model 1937 or 1938 anti-tank gun, the same which was mounted on most Soviet light tanks of the time. While certainly obsolete in tank warfare by mid-1941 standards, it would have proven useful against infantry and soft-skin vehicles and in decreasing the wear and ammunition use of the main gun.
The tank was also equipped with 4 DT machine guns (tank variant of the DP-27). One was in each of the small rotating cupolas. The other 2 were mounted coaxially to the left of the main gun and secondary gun, giving the crew great flexibility in engaging several types of threats at different angles simultaneously.
KV-2 testing 107 mm ZiS-6 gun, summer 1941. Source: State Archives
Tower of Babel
Kruchyonyh’s KV-4 was not seen as advantageous or having any original features and thus not rewarded. Its main drawbacks were the very high weight compared to other designs and the huge crew count of 9, while the GABTU had specified just 6 men. His convoluted 3 turrets stacked on top of another was likely seen as complicated, not revolutionary. In these regards, his design can be compared more to the KV-5, which would enter the design phase in May 1941. Despite weighing over 100 tonnes, the KV-5 had 170 mm of frontal armor and 150 mm of side armor, essentially making Kruchyonyh’s design pointless.
KV-4 as designed by G. Kruchyonyh, which was the heaviest design of them all, at 107 tonnes. Illustration by Pavel Alexe.
KV-4 Kruchyonyh specifications
Dimensions (L-W-H)
9.13 – 4.03 – 3.78 m
Total Weight, Battle Ready
107 tonnes
Crew
9
Propulsion
1,200 hp diesel/kerosene V-12 M-40 with 4 turbochargers
Speed
30 km/h (hypothetical)/h
Armament
107 mm ZiS-6
45 mm 20-K
4x DT machine guns
Armor
Turret: 130 mm
Front hull: 130 mm
Side hull:125 mm
Top: 50 mm
Belly:40 mm
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Soviet Union (1941)
