Category: WW2 Soviet Heavy Tank Prototypes

Soviet Union (1940-1941)
Heavy tank – 2 Prototypes Built

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-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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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 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.

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.

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.

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.

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:

• 3 exhaust manifolds burned over 284 km
• 4 drive belts broken off/burned (caused by improper alignment, sides got worn out)
• 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.

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.

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.

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 (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-5SN 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
No. Built	2 prototypes built

Sources:

Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
Victory Tank KV Vol.1 & 2 – Maxim Kolomiets
Tanks in the Winter War 1939-1940 – Maxim Kolomiets
Constructors of Combat Vehicles – N.S. Popov
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) – M. Svirin
TiV No.11 2014 (p.22-24) – I.V. Pavlov & M.V. Pavlov
TiV No.10 2013 (p.10-15) – I.V. Bach
Domestic Armored Vehicles 1941-1945 – A.G. Solyakin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
Малая модернизация КВ | Warspot.ru – Yuri Pasholok
КВ-3: набор танковой массы | Warspot.ru – Yuri Pasholok
Опытный танк с боевой биографией | Warspot.ru – Yuri Pasholok
Tank Archives: KV’s Replacements – Peter Samsonov
Tank Archives: Heavy Trials – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: T-150 Revival – Peter Samsonov
Tank Archives: Tank Plans for 1941 – Peter Samsonov
Tank Archives: Mass Breakdown – Peter Samsonov
Tank Archives: KV-3 Evolution – Peter Samsonov
Tank Archives: Tank RMA – Peter Samsonov
Tank Archives: Kirov Experiments, June 1941 – Peter Samsonov
Tank Archives: Kirov Factory Prototypes, March 1941 – Peter Samsonov
Tank Archives: KV-3 in Evacuation – Peter Samsonov
Tank Archives: Heavy Trials – Peter Samsonov

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 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.

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.

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.

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.

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.

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 (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
No. Built	Partial mock-up

Sources:

Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
Victory Tank KV Vol.1 & 2 – Maxim Kolomiets
Constructors of Combat Vehicles – N.S. Popov
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) – M. Svirin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
Малая модернизация КВ | Warspot.ru – Yuri Pasholok
КВ-3: набор танковой массы | Warspot.ru – Yuri Pasholok
Опытный танк с боевой биографией | Warspot.ru – Yuri Pasholok
Tank Archives: KV’s Replacements – Peter Samsonov
Tank Archives: Heavy Trials – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: T-150 Revival – Peter Samsonov
Tank Archives: Tank Plans for 1941 – Peter Samsonov
Tank Archives: Mass Breakdown – Peter Samsonov
Tank Archives: KV Gun Upgrades – Peter Samsonov
Tank Archives: Missing Index: KV-6
№ 189. Resolution of the Council of People’s Commissars of the USSR and the Central Committee of the All-Union Communist Party (Bolsheviks) No. 548-232ss “On the Production of KV Tanks for 1941”

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.

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.

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.

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.

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.

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 .

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.

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).

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.

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 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.”

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.

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.

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.

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.

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.

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.

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 / 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
No. Built	1 prototype built and saw service

Sources

Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
KV 1939-1941 – Maxim Kolomiets
Victory Tank KV Vol.1 & 2 – Maxim Kolomiets
Tanks in the Winter War 1939-1940 – Maxim Kolomiets
Constructors of Combat Vehicles – N.S. Popov
Domestic Armored Vehicles 1941-1945 – A.G. Solyakin
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) – M. Svirin
About the forgotten creators of Soviet armored power. (historyntagil.ru) – S.I. Pudovkin
Yuriy Pasholok. HF Small Upgrade – Alternate History (alternathistory.com) – Yuri Pasholok
Малая модернизация КВ | Warspot.ru – Yuri Pasholok
КВ-3: набор танковой массы | Warspot.ru – Yuri Pasholok
Опытный танк с боевой биографией | Warspot.ru – Yuri Pasholok
Tank Archives: KV’s Replacements – Peter Samsonov
Tank Archives: Heavy Trials – Peter Samsonov
Tank Archives: Heavy Tank Costs – Peter Samsonov
Tank Archives: T-150 Revival – Peter Samsonov
Tank Archives: Tank Plans for 1941 – Peter Samsonov
Tank Archives: Mass Breakdown – Peter Samsonov
Tank Archives: F-32 Technical Passport – Peter Samsonov
Tank Archives: Kirov Experiments, June 1941 – Peter Samsonov
How much cheaper than German tanks actually cost – Russian Seven (russian7.ru) – Kirill Shishkin
Heavyweight tanks KV-3, KV-4, KV-5 (famhist.ru)
https://sovetarmy.forum2x2.ru/t745-topic

Soviet Union (1944)
Heavy Tank – Drawings Only

Just months after the IS-2 began production, work began on developing a new heavy tank to replace it down the line. Engineer N. F. Shashmurin and his team envisioned an unusual tank, meant as a direct IS-2 upgrade, the IS-M. The most notable aspects of Shashmurin’s design were the large-diameter road wheels and the rear mounted turret. However, his project was not taken into consideration and was short-lived, although it did pave the way to the IS-6, which used some of its features.

Shashmurin and the IS

Tank designers are usually overlooked in the popular imagination, and those few acknowledged are usually limited to the likes of Ferdinand Porsche or Alexander A. Morozov. Even when limited to Soviet heavy tanks, the names of Nikolai L. Dukhov and Joseph Y. Kotin overshadow the others. Yet Nikolai Fedorovich Shashmurin was the man behind the creation of one of the USSR’s greatest war-winning tanks, the IS-2.

Born in 1910 in what at the time was called St. Petersburg (to be renamed Leningrad in 1924), Nikolai Fedorovich Shashmurin started his engineering studies at the Leningrad Polytechnic Institute in 1930 and graduated in 1936. By 1937, he had started to work at LKZ (Leningrad Kirov Plant) as an engineer for the SKB-2 design bureau. Before the war, he would work on the T-28 medium tank and create the torsion bar suspension system (T-28 No.1552) fitted on the SMK and U-0 (first KV-1 prototype), a system which would be implemented further on all future Soviet heavy tanks and self-propelled guns. Additionally, he developed gearboxes for the KV-1 (his gearbox would be dropped in favor of Dukhov’s infamous gearbox which would haunt the KV-1 for its entire service life), KV-220, KV-3, and even his own design for the KV-4 program.

With the beginning of the German siege of Leningrad in 1941, the LKZ (Leningrad Kirov Factory), specifically SKB-2 engineers, were evacuated to ChTZ (Chelyabinsk Tractor Plant) in Chelyabinsk (near the Ural Mountains), renamed ChKZ (Chelyabinsk Kirov Plant) a few weeks later. At Chelyabinsk, Shashmurin would develop the gearbox of the KV-1S and, after N. V. Tseits’ death in summer 1942, he became the head engineer for the KV-13 (at the time called IS-1), a vehicle which he did not like. Nonetheless, he would build upon it, and by May 1943, he had designed a new variant, equipped with an 85 mm D-5T gun specifically for the task of penetrating the German Tiger I, mated to a new hull. This was the Object 237 (at the time named IS-3), which would be adopted in service in September 1943 as the IS.

In parallel, Shashmurin designed the Object 238, meant to fit the new 85 mm S-31 gun in the KV-1S, but it was unsuccessful due to the cramped conditions within the turret. Production of the IS-1 started in November of that year, but it would not last long, as, by May 1943, work began on fitting the IS with the 122 mm D-25T gun, and by December 1943, the Object 240 would enter service as the IS-2. The mounting of such a powerful high-caliber gun was unprecedented in Soviet heavy tanks, which normally had similar, if not the same, guns as medium tanks.

Improving the IS-2

Extensive testing of the IS-2 was done at the NIBT (38th Research Test Institute of Armored Vehicle) proving grounds at Kubinka in January and February 1944, where it was concluded that the armor of the tank was not sufficient. Most notably, the “stepped” frontal hull was considered a weak spot, and it was proposed that the frontal hull should be made out of one angled plate.

Even after the first IS combat engagements, it became clear that, with the introduction of the German Panther tank, armed with a 75 mm KwK 42 L/70 (which could pierce the frontal armor of the IS heavy tanks) that the IS was insufficient. As early as September 1943, General Fedorenko (Head of the Armored Vehicle Directorate of the Red Army) would send a letter to Stalin, requesting the thickening of the IS armor and increasing its weight to 55-60 tonnes.

Additionally, in November 1943, the technical requirements for a new heavy tank were set by the GABTU (Main Directorate of Armored Forces). It was to have a mass of 55 tonnes, crew of 5, 160-200 mm of armor(frontal turret and hull), 800-1,000 hp engine, and a 122 or 152 mm gun. Speed was to be at least 35 km/h. These requirements would be laid down at the ChKZ plant on 3 December (10 December according to other sources) by factory director I.M. Saltzman.

The ChKZ SKB-2 design bureau, headed by N.L. Dukhov, had already worked on a new heavy tank since July, with its own funds. It was the 56-tonne K tank, which had 2 variants. The project was named Object 701. Only 2 K tank models were built.

However, on 21 March 1944, the GABTU changed the technical requirements. The weight was lowered to 55-56 tonnes, armament was a 122 mm gun with a muzzle velocity of 1,000 m/s, and 30 to 40 rounds had to be carried. The engine was to have a 1,000 hp output and allow for 40 km/h top speed. Armor thickness was not specified, instead, it was to be immune frontally to the Panther’s 75 mm KwK 42 L/70 and the 88 mm PaK 43/2 L/71 of the Ferdinand/Elefant.

These changes forced the reworking of the existing Object 701, but a green light was given the same month to produce 2 prototypes, leading to the IS-4 tank’s long development, with the first prototype, the Object 701-0, being built in May 1944.

At the same time as the developments at SKB-2, the other design institution at ChKZ, Factory No.100, also worked on their own tanks based on the same requirements. Headed by J.Y. Kotin, their approach was different to that of SKB-2. Instead of designing a new tank, they focused on a deep modernization based on the IS-2. By 18 April 1944, Factory No.100 would present its initial designs. Again, 2 models were built, one with a frontal plate separated into 3 parts (as on the first K tank) and one with a UFO-shaped hull, akin to the Object 279, designed and built decades later. Despite the increased protection, both variants had the same weight as the IS-2, 46 tonnes.

A document dated 8 April 1944, ordered J.Y. Kotin and his team to develop an upgraded variant of the IS-2 and subsequent SPGs over a 3-month period. The improvements should have included, but not been limited to, strengthened the armor protection, transmission, and chassis.

This would likely trigger the development of a new IS-2 modernisation, based on the requirements from 21 March. The design was to be less ‘radical’ and closer to the IS-2, but some very big changes were made. The tank would be called the breakthrough tank IS-M, the M standing for модернизация, meaning ‘modernisation’.

Sources do not agree exactly when development started, some arguing March, whereas others early April 1944. Nonetheless, N.F. Shashmurin was head of the project. While some design elements were taken from the previous upgraded designs, the main change was moving the turret to the rear of the hull, creating a very unique tank. A drawing of the tank would be made by Dobrovolsky. Who he was is so far unknown.

Design

The design of the IS-M was peculiar and unorthodox. The entire upper hull was made from several stamped steel plates, slightly angled inwards, with both the front and rear angled heavily. These were welded to the lower hull, which, while still mostly flat, had angled corners for extra weight saving. In addition to the main variant, a second variant was drawn out, with standard IS running gear. An SPG version was drawn as well, although only with very superficial details.

The IS-style turret was mounted at the rear of the hull, which allowed for very little gun overhang, decreasing the chance of the gun getting damaged in tight places such as forests and cities, or steep maneuvers, such as trenchcrossing. Despite its general shape being similar to the turret of the IS, several key components had been done away with, such as the big commander cupola or air vent.

Powerplant

The engine was to be an M-40 aviation engine, equipped with 4 TK-88 turbochargers. The displacement was of 61.07 l and had an output of 1,200 hp. Other sources claim it was a modified variant of the standard V-2-IS, such as the V-11 or V-16, yet these would only output between 500 and 700 hp, far less than the 800 to 1,000 hp specified. The M-40 engine was based on an aviation engine, thus could run on both diesel and kerosene. Whatever the engine was, it had a 10 h running time. The powerplant was kept inside an own compartment in the center of the hull, protecting the fighting compartiment and ammunition, consequently isolating the driver. Fuel tank was in the front, to the right of the driver. As the sprocket remained to the rear of the hull, the entire braking and final drive ensemble was kept at the rear, as on the original IS. However, this meant that the gearbox and driveshaft ran through the floor of the crew compartment. The transmission was likely offered in 2 variations, electromechanical, very similar to that on the Ferdinand/Elefant, or a conventional mechanical one. The gearbox was of planetary type.

For access to these components, the rear engine plate could be opened and rested on the hinges, for access to the final drive and brakes. The roof of the engine compartment was also removable, and had one engine access hatch, 4 air vents and 4 air purification filters.

Suspension

Two different running gear options were presented, one with 6 large-diameter road wheels, which allowed the returning track to rest on them, or 6 IS road wheels with 3 return rollers. The large road wheels would offer improved mobility over very muddy terrain, where smaller road wheels would clog up with mud. Additionally, they removed the need for return rollers. In turn, the standard IS wheel layout was already in use on various IS and KV series of tanks, resulting in a cheaper and smarter logistic choice. In both variations, the wheels were sprung by torsion bars.

Crew

The crew was larger than on the IS-2, with 5 men; a commander, gunner, loader, driver, and radio operator. The commander sat in the left corner of the turret. He had a low profile cupola equipped with 2 opposite facing periscopes for vision. Sat in front of him was the gunner, who operated the main gun. He had the main gun sight for vision and an extra, fully rotating periscope for a better field of view. Opposite him, to the right of the gun, sat the loader. He had to load the 2-part ammunition gun, as well as assist the commander in various tasks. For entry and exit, he had his own hatch with a periscope. The driver sat in the front of the hull, from where he would control the tank with 2 tillers. One direct vision slit in the armor was provided, as well as a fully rotating periscope. For ease of driving during the night and visibility during maneuvers, the tank had a single headlamp on the right side of the upper hull. The radio operator was likely seated to the driver’s right, also in the hull. He also had a rotating periscope for vision.

Armament

The exact armament of the IS-M was never specified, other than its caliber, 122 mm. However, considering the German-style muzzle brake, it was a D-25T, as on the standard IS-2. The tank was equipped with 40 shells for the main gun.

122 mm D-25T ammunition specifications
Shell type	APHE (BR-471)	APHE (BR-471B)	HE (OF-471)
Mass (kg)	25	25	25
Muzzle velocity (m/s)	795	795	800
Explosive	160 g	160 g	3.6 kg TNT
Penetration	200 mm	207 mm	42 mm (calculated)

Around the tank, 3 GVG 7.62 mm machine guns were mounted, one coaxial to the main gun, one in a ball-mount at the rear of the turret, and one in the frontal hull, which is not visible in the drawings. A ‘large caliber’ machine gun was to be added to the commander’s cupola for anti-aircraft purposes, likely a DhSK 12.7 mm machine gun, but it is not shown in the drawings either.

The SPG variant of the IS-M was likely armed with an 152.4 mm BL-8 gun, developed at the beginning of 1944 and tested during July of the same year on the ISU-152-1 (Object 246).

152 mm BL-8 ammunition specifications
Shell type	APHE (BR-540)	APHE (BR-540B)	HE (OF-540)
Mass (kg)	48.8	48.96	43.56
Muzzle velocity (m/s)	850	850	850
Explosive	0.66 g	480 g	5.86 kg TNT
Penetration	247 mm	276 mm

Armor

The frontal plate was a continuous flat plate of 200 mm angled at around 45°. Side armor was 160 mm thick and angled at 60° on the upper hull and flat on the lower hull. The rear was also heavily angled and 120 mm thick. The turret was 160 mm all around, but being awkwardly rounded, it increased its effectiveness significantly frontally. This gave the IS-M superior protection to any heavy tank of the time, while still maintaining a modest 55 tonnes weight.

Variants

In the background of the original drawing, 2 additional vehicles can be seen. The first is also an IS-M, but with a different set of running gear, namely 6 IS-style road wheels and 3 smaller return rollers. This was likely added as an alternative to the large roadwheel design.

Further back, a completely different vehicle is shown, a form of SPG based on the IS-M. The turret was replaced with a fixed casemate with a large 152 mm BL-8 gun. Interestingly, the running gear is the same as on the previously described IS-M.

Return to Leningrad and Further Developments

The IS-M was short-lived. Alongside its 2 earlier counterparts, all were abandoned in April 1944. Instead, Factory No.100 began work on a vehicle meant to rival the SKB-2’s Object 701 and thus become the new generation heavy tank. It would incorporate several features from both the IS-M and the 2 wooden mock-ups presented on 18 April 1944. This was the IS-6, designed at first in secrecy. Like on the IS-M, 2 variants were designed, one with large diameter road wheels and a steeply armored hull (Object 252). The second would use an electromechanical transmission on an IS-2 lower hull (Object 253).

In May, with the Soviets having lifted the Siege of Leningrad, the SKB-2 design bureau and Factory No.100 were moved back, and thus the LKZ was revamped. Many engineers moved back, including Shashmurin. Back in Leningrad, they would continue work on the IS-6. In August 1944, the Object 244 was used as a testbed for the Object 252’s wheels, first designed on the IS-M, and later the 122 mm D-30 gun. The Object 244 itself was a prototype dating back to February 1944, meant to test the new 85 mm D-5T-85BM on an unmodified IS-1 (Object 237). The project was named IS-3, although this has nothing to do with the later IS-3 heavy tank (Object 703). After a military representative from Factory No.100 reported the IS-6 secret development to the GABTU, it was ordered that further development and prototype production should take place at Uralmashzavod in Yekaterinburg, but without the end game of entering production.

Back at ChKZ, which had been working full-time on the Object 701, it was realized that it needed to present its own modernization of the IS-2. Thus, in August 1944, they presented the blueprints of an upgrade to the IS-2. At first glance, it looked like an unchanged IS-2, but it featured various improvements, such as refined frontal armor layout, thicker turret armor, improved turret design, and many mechanical changes, such as improved cooling system and engine room. Allegedly, one prototype was built. Yet, by October 1944, the project was abandoned in favor of a new tank, which incorporated many IS-2 features, but was still radically new. It was called the Kirovets-1 and given the Object 703 index. After several alterations, most notably the addition of its most famous feature, the legendary pike-nose, the IS-3 was born.

The pike-nose on the IS-3 was ‘borrowed’ from the IS-2U and Object 252U, an upgrade of the IS-2 and Object 252 meant to equip them with pike-noses. As a matter of fact, the IS-2U, designed in November 1944, was the last genuine attempt to fundamentally upgrade the IS-2 heavy tank. The IS-2 U’s turret was itself heavily inspired by earlier designs, such as the IS-M.

The IS-6 would end up unsatisfactory. The GABTU never intended to adopt it into service regardless. The Object 253 with the electromechanical transmission caught fire during testing. Both IS-6s were deemed insufficiently armored in comparison to the IS-4, and once the IS-3 was nearing production, the fate of the IS-6 was sealed.

Shashmurin himself, who had worked throughout the entire development of the IS-6, was never fond of the idea. Just like on the KV-13, he was a true believer in what he called “tank of maximum parameters” a tank which pushed the capabilities of the industry and designers to their limit, in an attempt to reach an unstoppable heavy tank. His first such vehicle was the IS-1 and later IS-2. For him, the IS-6 was a waste of time, especially considering the end of the war. As for the rivaling ChKZ heavy tanks, he had the following to say:

“We had finally created an almost perfect tank, capable of breaking through any enemy defenses. Ideal in its potential, all the qualities of the IS-2 could manifest themselves only in the development of the solutions found and tested in it. Alas, the improvement of the IS-2 was left to chance, and instead of developing already tested solutions, they began to invent new “bicycles”. An unjustified race began in the creation of independent models of heavy tanks, in many respects similar to the race that took place when creating the KV. The sad experience of the very recent past had taught us nothing…
The impressive, but unreliable IS-4 and IS-3 were being designed and created, another “monster” with two engines was being designed, a kind of electric locomotive was being built on tracks – a tank with an electromechanical transmission IS-6, which burned down after driving through the factory yard only 50 meters. In general, the design idea was in full swing, and in the meantime, the fighting was done by the “rude” workers of the IS-2, and not by the “handsome” IS-3, the production of which began in the early ‘45 and which immediately began to break down with the regularity of the sad memory of the KV-1.”

After the war, Shashmurin would finally fulfill his dream of designing a true “tank of maximum parameters”, the IS-7, which indeed, pushed the technology of the time to its limits, being the heaviest Soviet tank ever built, as well as several work on ATGM-based heavy tanks, PT-76 and more.

Conclusion

The IS-M itself was a short-lived design meant to offer an arguably unnecessary upgrade to the IS-2. It would incorporate some very interesting features and solutions, such as a rear mounted turret, large diameter road wheels, and a curved hull. It alo took in consideration several running gear designs and an SPG layout. Nonetheless, despite its short life, it was a crucial factor in the developmental progress of Soviet heavy tanks during the Second World War, by leading directly into the development of the IS-6, which lost in turn to the more refined, though still crude, IS-3 and IS-4 designed at ChKZ. For Shashmurin, the IS-M was certainly not his most prideful creation, but through its odd nature, it complements well the career of one of the USSR’s most important heavy tank designers of the Second World War.

IS-M specifications
Dimensions (L-W-H)	7 x 3.2 x 2.7 (m)/td>
Total Weight, Battle Ready	55 tonness
Crew	5
Propulsion	1,200 hp diesel (V12) M-40 with 4 turbochargers or 500-700 V series engines
Speed	40 km/h
Armament	122 mm D-25T 3x GVG machine guns 1 (?) DhSK machine gun
Armor	Turret: 160 mm (hull) front: 200 mm Sides: 160 mm Rear: 120 mm Roof and belly: 30 mm
Total Production	0, drawings only

Sources:

IS Tanks – Igor Zheltov, Alexander Sergeev, Ivan Pavlov, Mikhail Pavlov
Supertanki Stalina IS-7 – Maxim Kolomiets
Heavy Tank IS-4 – Maxim Kolomiets
Tank Power of the USSR – M. N. Svirin
Modest genius: who created the IS-2 tank, which became a symbol of Victory – Rossiyskaya Gazeta (rg.ru) – Sergey Ptichkin
Holes in the armor -Sergey Ptichkin, Sergey Zykov
Tank Archives: Modernization on Paper – Yuri Pasholok, Igor Zheltov, Kirill Kokhsarov
Tank Archives: Wrong Place, Wrong Time – Yuri Pasholok
IS-2: Struggle for the Assembly Line | Warspot.net – Yuri Pasholok
Not in the amplitude of the | Warspot.ru -Yuri Pasholok
Muzzle wedge for heavy tank | Yuriy Pasholok | Zen (dzen.ru) – Yuri Pasholok
Tank Archives: Improving the IS-2 – Peter Samsonov
“>Russian Heavy Tank Object 244 – The Original IS-3 (thedailybounce.net) -Harkonnen
IS-2Sh – unusual “Stalin” (voentex.ru)

Soviet Union (1944-1945)
Heavy Tank – None Built

The Panzerkampfwagen VI “Tiger” Ausführung E is one of the most outstanding and iconic vehicles in the history of tank building. The Tiger caused significant problems for the Allies when it first appeared at the front. Fortunately for the Allies, shortly after, several vehicles were captured by the Red Army and tested. In the Soviet Union, designers even worked on the option of re-equipping this German heavy tank with ‘domestic’ Soviet guns. However, this project appeared too late, and the imminent end of the war did not give this proposal any chance to materialize.

The Heavy Cat of the Wehrmacht

The Tiger I, or ‘Panzerkampfwagen Tiger Ausführung E’ (Pz.Kpfw.Tiger Ausf.E), was born in May 1942, but its conception and development can be traced directly back to 1936 and 1937, with work on a 30-33 tonne tank by the firm of Henschel und Sohn in Kassel. Just like other German tank projects, the development was very complex, overlapping with dozens of other projects, and has been the subject of a large number of books and movies. The name ‘Tiger’ itself has a no less complex history. It was first used in February 1942, when the project “Pz.Kpfw.VI (VK45.01/H) Ausf.H1 (Tiger)” was approved. The design was clearly identified as the Pz.Kpfw.VI or Tiger, with “Tiger I” first used on 15th October 1942, followed by “Pz.Kpfw.VI H Ausf.H1 (Tiger H1)” on 1st December 1942 and then “Panzerkampfwagen Tiger Ausf.E” in March 1943.

The Tiger I had a crew of five: commander (back left), gunner (front left), and loader (right) in the turret, and the driver and radio operator in the front left and right of the hull, respectively.
The main armament consisted of the 8.8 cm Kw.K. 36 L/56 gun in the turret. This gun was derived from the 8.8 cm Flak 18 and Flak 36 AA guns and delivered similar ballistic performance. It was combined with the excellent T.Z.F.9b 2.5 x magnification binocular telescope for the gunner. This T.Z.F.9b binocular sight was later replaced by the cheaper but no less effective T.Z.F.9c monocular sight, a change identifiable by the switch to a single hole in the left side of the mantlet. The Tiger carried 92 rounds of Armor-Piercing (AP) and High Explosive (HE) ammunition. Where available, the Pz.Gr.40 (high velocity, sub-caliber, tungsten core, with no explosive filler) round was also carried for use against heavy enemy armor.

Secondary armament consisted of a 7.92 mm MG.34 machine gun mounted coaxially with the main gun. This weapon had a maximum elevation of -8º to +15º. A second machine gun, a ball-mounted MG.34, was located in the right-hand side of the driver’s plate. This second machine gun was capable of 15º traverse to either side (total arc of 30º) and an elevation of -7º to +20º. It was fitted with a K.Z.F.2 episcopic sighting telescope with a magnification of x1.75. For these machine guns, 4,500 rounds of ammunition were carried. Another M.G.34 anti-aircraft machine gun (Flieger-M.G.) could also be carried on the turret (also fitted to the Befehlswagen-Tiger).

After June 1942, six 95 mm diameter smoke grenade launchers (in two sets of three) were approved for mounting on the turret, a process which started in August 1942. The launchers could fire the Nb.K.39 90 mm smoke generator grenades but, following combat reports of gunfire setting them off and blinding the crews, these were dropped in June 1943.

The Tiger was powered in the early production runs by the HL 210 TRM P45 21-liter V-12 Maybach petrol engine producing 650 hp at 3,000 rpm. Due to problems with the reliability of this engine, the maximum performance could not be achieved, restricting mobility for this heavy tank. As a result of the poor performance, the more powerful HL 230 TRM P45 23 liter V-12 Maybach engine producing 700 hp was introduced in its place from May 1943 onwards.

The Tiger’s suspension consisted of 55 mm diameter torsion bars (Stabfedern), which ran the complete width of the tank’s hull, with splined heads, although the two front and rearmost two bars were wider than the rest, at 58 mm diameter. The bars were connected to the road wheel arms (Laufrad-Kurbel), each of which had three road wheels. Their arrangement overlapped wheels from adjacent road wheel-arms, creating an interleaved pattern to spread the load of the tank onto the track. Hydraulic shock absorbers were fitted to the inside of the front and rear road-wheel arms which, combined with the damping effect of the torsion bar, created a very smooth ride.

Unsuccessful Debut

On 29th August 1942, the first batch of Tigers from the 502nd Heavy Tank Battalion, consisting of four Pz.Kpfw. VI, advanced to combat positions from the railway station Mga, near Leningrad. Three vehicles suffered serious breakdowns leaving the station, and, in general, were not so successful. Later, during the battles to break the blockade of Leningrad, on 16th January 1943, Soviet troops captured a Tiger which was previously hit by artillery. This was followed by a practically intact one on 17th January. The crew left it without destroying even a brand-new technical passport, different tools, and weapons. Both tanks were evacuated from the combat area and sent to the Kubinka Proving Ground for studies.

Studying the «Wild Beast»

Initially, the captured tanks appeared in the correspondence as “captured tanks of the HENSHEL type”, later called T-VI. The tanks that arrived aroused great interest among the Soviet military command. By that time, the “Tigers” were actively used by the Germans both on the Soviet-German front and in North Africa. These vehicles were used for the first time on a truly massive scale during the battle for Kharkov, making a significant contribution to the defeat of the Red Army on this sector of the war front. Around the same time, the Tigers fought in Tunisia against American, British and Commonwealth troops, inflicting serious losses on them.

By April 1943, the two tanks, with turret numbers 100 and 121, were already at the proving ground. It was decided to test ‘121’ for armor durability and use ‘100’ for testing the gun against the armor of Soviet tanks.

The armor on the side of the Tiger’s hull managed to withstand the Soviet 45 mm guns. However, 57 mm guns of the ZiS-2 type overcame the 80 mm side armor with ease even from a long distance (up to 1 km). The frontal armor of the tank could not be penetrated by the 76 mm F-34 gun, the main Soviet tank gun at that time. The 85 mm “anti-aircraft gun” 52-K performed much better in this regard, penetrating the “Tiger” in the front from a distance of 1 km. The 122 mm A-19 gun performed the best at this. Until that moment, it had not yet been considered as a possible tank cannon. After two hits fired from it, the once formidable German heavy tank turned into a pile of scrap metal.

The tests of the German 88 mm tank gun were much more impressive. It was used to fire at Soviet T-34 and KV tanks. The main Soviet heavy tank of that time was easily penetrated from a distance of 1.5 km. Even the uparmored version with additional protection was also penetrated. For the T-34, the very first shot, from a distance of 1.5 km, “decapitated” the tank. Its turret was “knocked off” the hull, while significant damage to the frontal part of the hull was caused by further shelling. It is worth noting that the aforementioned Soviet anti-aircraft gun 52-K showed similar results in tests.

Tests of the new German heavy tanks showed the Soviet military command the need to gradually abandon 76 mm tank guns in favor of larger calibers, such as 85 mm and 122 mm. At around the same time, accelerated work began on self-propelled guns, such as the SU-85 and SU-152, as well as on the KV-85 and IS-1 heavy tanks.

A Stranger Amongst Us

The sporadic capture of workable versions of the Tiger tank by the Red Army was the main reason for the episodic nature of its combat use on the side of the USSR. In addition, Soviet tankers, in an effort to get a high reward, almost always destroyed the rare Pz.Kpfw. VI.

The first reliable case of the use of a captured “Tiger” in battle was recorded only at the very end of 1943, with the crew under the command of Lieutenant N.I. Revyakin from the 28th Guards Tank Brigade. On 27th December 1943, one of the “Tigers” of the 501st Tank Battalion got stuck in a crater, its crew ran away, and the tank itself was captured. On the next day, the tank was assigned to the 28th Brigade. Revyakin was appointed commander of the captured heavy tank because he already had extensive combat experience and military awards, two Orders of the Patriotic War of the 1st degree and the Order of the Red Star. On January 5th, the captured tank, with red stars painted on the sides of the turret and with the writing “Tiger” added as well, went into battle.

The operational service of this vehicle with Soviet units looked quite typical for German heavy tanks. It almost always required repairs. The matter was greatly complicated by the lack of spare parts. But this was on the battlefield. In the bowels of the Soviet design bureaus, there had been several projects developed to re-equip captured German vehicles with Soviet guns since 1942. Similar proposals were made for the Tiger, but they started much later, at the end of 1944 and the beginning of 1945.

T-VI-100: Unrealized “Frankenstank”

On 28th November 1944, the Artillery Committee at the Main Artillery Directorate of the Ministry of Defense of the USSR (AK GAU) issued tactical and technical requirements No. 2820 “For the installation of domestic weapons in the turrets of captured German tanks T-IV, T-V, T-VI and the Royal Tiger” (due to the lack of a full-scale model of the Pz.Kpfw. VIB Tiger II turret, the study of the change of armament of this tank with a domestic gun was not carried out), including the adaptation of these turrets as stationary firing structures. Simply put, OKB-43 needed to take the turrets from captured tanks, replace the German guns with Soviet ones, along with sights, and further adapt them for installation on armored vehicles.

In January 1945, GSOKB (рус. Государственное Союзное Особое Конструкторское бюро – State Union Special Design Bureau) No. 43 at the NKV (рус. Народный Комиссариат Вооружения СССР – Ministry of Armaments of the USSR) presented a project for installing the latest 100 mm D-10T tank gun, which in the future would become the main armament of the T-54 medium tank, with the Soviet TSh-17 sight, in the turret of the T-VI tank (how trophy “Tigers” were designated in the USSR) while retaining its gun mantlet. This conversion process was estimated at 90 hours of work. The conversion provided for the installation of a shell casing removal system, which simplified the work of the turret crew.

№	Works	T-IV-76 with F-34	T-V-85	T-VI-100	T-IV-76 with ZiS-5
I	Lathing	18.0	40.0	15.0	9.0
II	Gouging and milling	4.0	7.0	4.0	5.0
III	Drilling	10.0	10.0	9.0	9.0
IV	Welding	16.0	22.0	12.0	12.0
V	Gas cutting	8.0	8.0	7.0	8.0
VI	Forging, pressing and bending works	4.0	6.0	6.0	4.0
Summary		60.0	93.0	53.0	47.0
Fitter and assemblyman hours, 5 people per team		80.0	120.0	90.0	80.0
Head of Special Design Bureau (OKB-43) – Salin; Senior technologist – Petrov;				January 3, 1945

New gun: D-10T

At the end of 1943, on an initiative basis and in the shortest possible time, the team of designers of Design Bureau of Plant No. 9, headed by F.F. Petrov, developed a 100 mm gun system designed for installation in the SU-100 tank destroyer. The cannon, the lead designer of which was M.E. Bezusov, received the designation D-10. The barrel length was 56 calibers (5,610 mm), and the initial velocity of the projectile was 900 m/s. The rollback length of the D-10S turned out to be longer than that of its competitors and was about 510-560 mm. Structurally, the gun system was a logical successor of the Design Bureau of Plant No. 9’s earlier projects, and when it was created, maximum unification with them was achieved. For example, cradle, lifting and turning mechanisms were taken from the D-25T 122 mm gun.

The history of the 100 mm D-10 gun did not end with the SU-100 tank destroyer. It would also appear on such Soviet late-war prototypes as the T-34-100 and SU-101 (a.k.a. Uralmash-1). After the war, it would be modified many times (hence versions like D-10T, D-10T2, M-63, D-33, 2A48, etc.) and become the main gun of the Soviet medium tanks of that period, the T-54 and T-55. It would also be proposed for some Cold War Soviet tank destroyers, such as the SU-100P and the Obj. 416, for Chinese medium tank Type 59 (WZ-120), and for light amphibious tanks prototypes, such as the Obj. 685 and the Obj. 934.

Project Description. Comparison with Tiger I Ausf. E

The Soviet military command liked the proposal of the installation of the Soviet D-10 gun, which had proven itself on SU-100 self-propelled guns, in the turret of the German Tiger tank. Indeed, the 88 mm KwK 36 tank gun, so formidable in the early stages of the war, was no longer that impressive by 1945. This was understood by the Germans themselves, who managed to design a lot of self-propelled guns armed with a 128 mm KwK 44 gun, and one of them, the JagdTiger, was even built and used in battle.

8,8 cm KwK 36	APHEBC		APCR	HEAT	HE
	PzGr	PzGr 39	PzGr 40	HIGr 39	SprGr
	9.5 kg	10.2 kg	7.3 kg
	810 m/s	773 m/s	930 m/s	600 m/s	820 m/s
	168 g charge (285.6 g TNT eq.)	64 g charge (108.8 g TNT eq.)	–	0.646 kg charge (1.1 kg TNT eq.)	689 g TNT
	146 mm pen	165 mm pen	210 mm pen	110 mm pen	–
	7-8 rpm	Parameters of penetration are given for 0 m and 0°.

Original T-VI gun… (source — ZA DB, Pablo Escobar’s gun table)

100 mm D-10T	APHE		HE
	BR-412	BR-412B	OF-412
	16 kg		15.2 kg
	895 m/s		880 m/s
	65 g charge (100.1 g TNT eq.)		1.46 kg TNT
	210 mm pen	215 mm pen	–
	7-8 rpm	Parameters of penetration are given for 0 m and 0°.

… and a Soviet “replacement” for the T-VI-100 proposal (source — ZA DB, Pablo Escobar’s gun table)

The Soviet gun significantly surpassed the KwK 36 in terms of firepower. With comparable accuracy, it had higher penetration, muzzle velocity, and much more powerful HE shells. With all the ‘pluses’, it was only slightly inferior to the German gun in terms of rate of fire.

The larger caliber affected two technical characteristics of the vehicle, the elevation arc and the amount of ammunition. According to the author’s estimates, instead of 92 shells of 88 mm caliber in the German original, the T-VI-100 could carry only about 50 shells of 100 mm caliber. The dimensions of the breech and the shape of the barrel influenced the downward elevation arc of the gun: instead of -8° in the frontal part and -3° in the rear in the Tiger I Ausf. E, the maximum depression became -4° all around. The upward elevation arc of the gun remained the same at +15°.

Inside the turret, space became much tighter. The breech of the new gun would now occupy ~75% of the turret length instead of 50% previously.

The cannon was not the only German component replaced with a domestic one in the proposal, with the coaxial machine gun as well as the sight being changed. The German 7.92 mm MG-34 was substituted with the Soviet 7.62 mm DT with a disk magazine, while the German TFZ-9 sight was replaced by the Soviet TSh-17. In the future, the same sight would be used on IS-2 and IS-3 Soviet tanks. It can be assumed that the machine gun in the hull would also have been replaced by a DT. Although there is no documentary substantiation of this hypothesis, such a decision would have been logical.

However, many other problems remained unresolved. There was no talk of replacing the transmission, engine, and other hull components with Soviet ones, which means that repairing them would have been problematic. Obviously, if the T-VI-100 was built in metal, in field use, all the ‘charms’ of exploiting captured German vehicles by the Red Army would have been preserved to the great displeasure of the crews and mechanics.

The Fate and Prospects of the Project

In general, the project was judged positively and was approved by the High Command, but things did not move beyond the project documentation. By spring 1945, the need for such projects had disappeared due to the proximity of the end of the war in Europe.

The Tiger I itself was outdated by 1945. Its armor could no longer ‘surprise’ anyone. All this indicates that the T-VI-100, if built, could not fulfill the previous role of “heavy tank for breakthroughs”, which was performed by the Tiger I in the first years after its appearance at the front.

It seems, however, that there was another possible option for using the developments on the project, selling a “modified” version to third countries. However, the logic behind this seems flawed, as most of these, especially those that never operated such a heavy tank before, the “Tiger”, even with a 100 mm gun, would probably not have been needed (and Germany itself was already not allowed to have its own army). For the emerging Soviet-bloc countries, such as Czechoslovakia, Hungary or Poland, especially ones bordering what would in the future become NATO, the T-VI-100 might have been a good temporary stopgap for their weakened armies until Soviet supplies of T-34-85s, IS-2s, T-54s, etc. would have become the norm. It is important to keep in mind that plans including Operation Unthinkable, a British invasion of East Germany, were actively developed, and tremendously dangerous for the weakened and war-torn USSR and its satellites at that time. Moreover, the first frontier of the possible Third World War would surely have been in Eastern Europe. On the other hand, it is doubtful that rearming a quite rare and outdated captured tank type was easier and more useful for the aforementioned countries rather than waiting for the mass-produced T-34 or IS-2.

Conclusion

The project of the T-VI-100 tank, like many of its analogs, belongs to the category of “the war ended too soon”. On the one hand, although this was a fairly reasonable alternative to the simple disposal of captured vehicles, serious improvements were still required for its full-fledged and practical implementation, especially to the hull. On the other hand, for one of the tasks of the project (the aforementioned possibility of using turrets with a new gun system as stationary firing points), the existing level of development was more than enough. But such defensive systems would have also hardly been needed by the Soviet Union after 1945.

Instead of an Afterword: T-VIB-100

As mentioned above, captured King Tigers were also considered for rearming with domestic (Soviet) weapons, but these proposals were not worked on due to the lack of turrets and data on them.

Still, it can be speculated what exactly may have been included in the hypothetical ‘domestication’ of the “Tiger-B” (or “T-VIB”), as it was called in the USSR. TZF-9 sights, just like on T-VI-100, would likely have been replaced by the TSh-17. The 7.62 mm DT machine gun would have likely taken the place of the MG 34.

A more difficult question is which Soviet weapon could have replaced the German 8.8 cm KwK 43. The choice would probably have been between the 100 mm D-10 and the 122 mm D-25 tank guns (there is no sense in replacing KwK 43 with less powerful guns of smaller caliber). Since the second variant, due to its large caliber, would require a large amount of space (for the breech, counter-recoil mechanism, and ammunition), the D-10 seems to have been the most optimal alternative to the German gun.

The vehicle itself would probably have been named similarly to the T-VI-100: T-VIB-100, but “Tiger-B 100” variant is also possible. However, all this is just a hypothetical conception and speculative thought of “what-could-have-been”, and was never actually developed.

Special thanks from the author to his colleagues Andrej Sinyukovich, Pavel “Carpaticus” Alexe and Pablo Escobar.

T-VI-100 specifications table
Dimensions (L-W-H)	8.45 x 3.547 x 3 m
Total weight, battle ready	~57 tonnes
Crew	5 (commander, gunner, loader, driver, and radio operator)
Propulsion	Maybach HL 210 P.30 petrol engine (650 hp) or Maybach HL 230 P.45 petrol engine (700 hp)
Performance	45 km/h (road max.), 30 km/h (road sustained) or 40 km/h, 20-25 km/h (firm ground sustained)
Fuel	348 liters, sufficient for a range of up to 120 km road, 85 km firm ground. Two spare 200-liter fuel drums could be carried on the back deck for long road marches.
Primary Armament	100 mm D-10T
Secondary Armament	2x 7.62 mm DT
Gunner’s sight	TSh-17
Ammunition	~50 rounds 100 mm, ~4,500 7.62 mm ammunition
Hull Armor	Driver’s plate – 100 mm @ 9º Nose – 100 mm @ 25º Glacis 60 mm glacis @ 80º Hull Sides Upper – 80 mm @ 0º Hull Sides Lower – 60 mm @ 0º Rear – 80 mm @ 9º Roof and Belly – 25 mm
Turret armor	Mantlet – 120 mm @ 0º Front – 100 mm @ 5º Sides and Rear – 80 mm @ 0º
№ built	0, blueprints only;

Sources

Central Archives of the Russian Ministry of Defense 81-12038-775;
Russian State Archive of Film and Photo Documents;
https://tanks-encyclopedia.com/ww2/germany/panzer-vi_tiger.php
https://waralbum.ru/41232/;
https://warspot.net/38-heavy-trophy;
https://pastvu.com/p/105441;
http://www.tankarchives.ca/2013/05/re-arming-german-tanks.html;
http://www.dogswar.ru/artilleriia/pyshki-gaybicy/7576-100-mm-nareznaia-tan.html;
Pablo Escobar’s guns’ parameters table;
https://vk.com/@zinoviy_alexeev-t-vi-100;

Soviet Union (1932)
Heavy Tank – 2 Prototypes Built

The T-35A tank is one of history’s strangest tanks – often seen crawling across the Soviet inter-war era parade squares. This tank grabbed the hearts, souls, and imaginations of the Soviet people and foreign military attachés alike. It was one of the many proud achievements of Soviet industrialisation – its image appeared on posters, films, and even medals and awards!

Prototypes

In the late 1920s and early 1930s, the USSR was desperate for a modern army. After hard fighting during the Civil War (1918-1920), the vehicles of the Red Army were worn out and obsolete. These consisted mostly of obsolete Mark V heavy tanks and Medium Mark A Whippets.
Designing and mass-producing a new vehicle would help the fledgling Red Army set foot on the international stage again. It would also give Soviet engineering a fantastic opportunity to put its skills to the test, which were comparatively primitive to those of the USA and Great Britain in the late 1920s.
However, as Soviet engineering was still in its early stages of modernization, and as Soviet engineers had little to no experience designing tanks, it was decided to outsource Soviet tank designing to foreign sources. This came in three different types. The USSR would either pay for engineers to come to the Soviet Union and help build tanks, buy blueprints from foreign powers and visit tank factories or outright purchase foreign tanks wholesale and begin local manufacture.
In the heavy tank department, the German engineer Ernst Grotte was brought in from Germany, a country banned from tank development. Between 1929 and 1931, his design team came up with the TG tank. Grotte was assigned to the Leningrad AVO-5 design bureau.

TG Tank

The TG tank was a large tank with two independent tiers of armament. The lower elliptical turret was equipped with an A-19 76.2mm (3 inch) gun, and a rotating turret mounted on top of the first one which was fitted with a 37mm (1.46 inch) PS-2 gun. The suspension consisted of coiled springs, and each side of the vehicle had five large diameter road wheels.
The TG tank also had three water-cooled 7.62mm (0.3 inches) Maxim machine guns, one on either side of the hull and one at the rear of the machine. The vehicle weighed 20 tonnes, The tank was powered by the M-6 Aero-engine and could reach a maximum of 35 kilometers per hour (22 mph). The TG had a crew of 5.

The TG Tank during trials. The turret ring for the main turret broke, therefore tests were conducted with the turret permanently facing forward. Source: Military Images
The vehicle was tested in April 1931 and was quite successful, displaying good cross-country capabilities, relatively good speed, and reliability. A noted flaw though, was that the fighting compartment of the vehicle was very cramped.
However, the TG project was dropped, not due to the vehicle’s performance, as this was better than other Soviet prototypes at the same time, but rather due to costs. It would cost almost 1,500,000 roubles to manufacture a single such tank, money better spent on manufacturing up to twenty-five BT-2 fast tanks.

The TG tank incorporated many modern ideas, however, it was an inherently flawed vehicle. Source: panzernet

The TG tank in 1940. Nothing more than a display piece at the Polygon near moscow. Source: panzernet

Unrelated to the Independent

Some allege that the T-35 was inspired by the British A1E1 Independent tank, but Soviet-era sources claim that the A1E1 had no influence on the design, despite Soviet knowledge of the vehicle. Indeed, apart from the layout of the turrets, the T-35 and A1E1 are very different machines.

The British A1E1 independent tank. Even a quick inspection will reveal that the machine is vastly different to even the prototype T-35-1 and T-35-2. Illustration by David Bocquelet.
Soviet engineers were given the opportunity to inspect the A1E1 Independent tank when advisors from the USSR visited the Vickers factory in 1930. However, they found the same flaws in the machine as the British did, i.e. that the tank was too long and too thin, and the tank’s sides were prone to warping under the tension of the tracks.

T-35 specification
Dimensions (L-w-h)	Unknown
Total weight, battle ready	35 Tons
Crew	9
Propulsion	M-6/ M-17L Aero engine
Armament	1x Ps-3 76.2mm, 2x Ps-1 37mm, 4x 7.62mm
Total production	2

Links, Resources & Further Reading

Fallen Giants: The Combat Debut of the T-35A Tank – Francis Pulham
Land Battleship: The Russian T-35 Heavy Tank – Maxim Kolomiets & Jim Kinnear
aviarmour.ru

ww2 Soviet Tanks Poster

T-35-1 and T-35-2

A new heavy tank prototype was designed in early 1932, designated ‘T-35-1’. It was produced at the Kharkov Locomotive and Tractor Works (KhTZ). This first prototype had six pairs of road wheels arranged with two pairs of road wheels per bogie. Each bogie was fitted with coiled spring suspension comprised of two pairs of springs. The name T-35 comes from the Red Army requirement for a 35-ton tank.

Both the T-35-1 and T-35-2 were paraded in 1933 on palace square. Notice the round turret roof of the T-35-1. Source: pinimg.com
All the sub-turrets of the prototype were of the same design and shape regardless of armaments. Two of the turrets were equipped with the 37 mm PS-2 guns and the other two having DT-29 machine guns. When facing forward and aft of the tank, the 37 mm turrets were on the right, while the machine gun turrets were on the left. The main turret was fitted with a 76.2 mm PS-3 gun and another machine-gun in a ball-mount to the right of the gun. It was welded with distinctive curved roof and rested on an armored pedestal.
The tank had two armored skirts on either side to protect the suspension. However, rather foolishly, the skirts of the first prototype had no access ports and there was no way to access the suspension without pulling the skirts apart. The tank was powered by the M-6 aircraft engine, with the drive wheel at the rear. The tracks ran on top of 6 return rollers that were almost two meters above the ground.

The T-35-1 turret was removed at some point when the tank was dismantled. Here it sits at the Polygon in 1940. Source: Sergey Lotarev
The prototypes had crews of 9, a driver, engineer/ hull machine gunner, a single crew member in each of the four small turrets, and three crew in the main turret. The driver and engineer were equipped with dome-type escape hatches on the front hull roof.
This prototype was evaluated in mid-1932 before a second prototype was ordered. The second prototype was outwardly similar, with the exception of the addition of access ports in the skirts. These were square shaped and gave all-important access to the bogies for maintenance. In addition, the main turret relinquished the round roof.

The T-35-2 can be harder to distinguish from production T-35s, however inspection of the drivers compartment with the hull machine gun and the escape hatches clearly reveals its origin. Source: www.battlefield.ru
The powerplant of the second prototype was changed to the new M-17L Aero Engine. This was the Soviet copy of the BMW VI Aero engine. Accordingly, this prototype was called the ‘T-35-2’.
These T-35 prototypes were both evaluated but were not accepted for Red Army service. This was due to a new design buro designing a similar, yet superior machine.
The OKMO of Kharkov, in parallel with the T-35-2, had designed the T-35A prototype. Similarly to how the T-37 and T-37A were different vehicles with similar names, the two tanks shared similarities but were, by and large, different vehicles.

Visual Identification Guide

The two T-35 prototypes are discernable from production T-35A tanks through a multitude of factors. The main way of identification is by the placement of the exhaust pipes lengthwise on the rearmost fenders. Production T-35As had their exhaust lying sideways on the central hull, and in later tanks, this was moved under armor.
The turrets too are different. The main turret of the T-35-1 had a distinctive round roof, and the T-35-2 is missing much of the exterior detail that production T-35As had. The main gun in the main turret was also a PS-3 76.2mm gun rather than the KT-28 76.2mm gun of production tanks.

The front of the T-35-1. Notice the two driver’s positions. Source: Land Battleship T-35
The sub turrets on the two prototype tanks were all identical to each other, whereas production T-35s 45mm gun turrets were larger than the machine gun turrets, and were cylindrical in shape.
Hulls too were very different, with the prototype T-35-1 and T-35-2 having only six road wheels per side, whereas production tanks had eight road wheels. The entire nose of the vehicle was different, with the two prototypes having round bulbous escape hatches for the driver and engineer. Additionally, there was a hull-mounted machine gun position on the prototypes absent from production tanks.

One of the production T-35A’s. Notice the vast differences between this machine and the prototypes. Source: Land Battleship T-35

Conclusion

The two T-35 prototypes, while sharing the name and basic layout with the T-35A, was, in reality, an entirely different machine. It is clear inspecting the dimensions and the armaments that the prototypes were inferior in almost every way to the production T-35As.
While a useful jumping-off point, these prototypes were technical failures. The production tanks heavily differed from these prototypes, so much so that pre-Glasnost western sources called these prototypes “T-32”. This is, of course, wrong.

T-22 Tank Grotte prototype

T-35-1 prototype
Both Illustrations by Tank Encyclopedia’s own David Bocquelet

Fallen Giants: The Combat Debut of the T-35A Tank

By Francis Pulham

The Soviet T-35A is the only five-turreted tank in history to enter production. With a long and proud service history on Soviet parade grounds, the T-35A was forced to adapt to the modern battlefield when the Second World War broke out. Outclassed and outdated, the T-35A tried to hold its own against the German invaders to no avail. For the first time, actual battlefield photographs have been cross-referenced with maps and documents to bring about the most complete look at the T-35A in the Second World War to date.

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