WW2 Soviet Prototypes

T-27 37 mm Projects

Soviet Union (1931)
Experimental Self-Propelled Gun – At Least 2 Prototypes Built, Possibly A Small Production Series

During the 1920s, the Soviet Army was rather poorly armed and equipped. As it was slowly built, the need for armored vehicles, such as tanks, arose. The initial attempt to develop domestic tank design failed, as the Soviets lacked experience in designing such vehicles. For this, a military delegation was dispatched to countries, including the United States and Great Britain, in hope of acquiring a foreign design that was to be built under licenses. From Britain, the license for the Carden Loyd tankette was acquired. The Soviets further improved this design, which led to the creation of the T-27 tankette. As it was only armed with a machine gun, the Soviets wanted to increase its firepower by adding a 37 mm gun, creating a small series of experimental vehicles.

The experimental T-27 was armed with a 37 mm gun. Source: Svirin M. N. Самоходки Сталина. История советской САУ 1919-1945

The T-27’s Brief History

During the 1920s, the Soviet armored forces were in a process of reorganization and rearmament. Initial Soviet attempts to develop armored vehicles were rather unuseful, and only smaller series were built. The first domestically built tank, the T-18 (MS-1), was adopted in small numbers to service in July 1927. Soviet industry was experiencing constant delays in delivery and poor quality of production. In November 1929, Управление по механизации и моторизации – YMM (English: Department of Mechanization and Motorization – UMM) instructed that the current development situation was unfeasible in the near future. To remedy this situation, YMM was instructed to seek technological help abroad.

On 30th December 1929, a commission led by the head of the UMM, Innokentii Khalepskii, went abroad. The plan was to visit Czechoslovakia, France, Germany, Great Britain, and US in order to purchase technologies and armaments. The negotiation with Great Britain proved most promising, as the Soviets managed to purchase a few different tank designs, including the Vickers Carden Loyd tankettes, the Vickers-Armstrong 6-ton, and the Mk.II medium tanks.

Vickers Carden Loyd tankette. Source:

Some of the newly acquired Carden Loyd Mk.VI tankettes were sent to Zavod No.37, a factory in Moscow. There, an engineering team led by N. Kozyrev examined this vehicle in great detail, in order to be put into production as quickly as possible. The Soviet engineers were generally satisfied with this vehicle, but noted a number of shortcomings. Consequently, they implemented a series of improvements (such as modifications to the suspension, adding a stronger engine, etcetera) before the vehicle under the name T-27 was finally accepted for service.
The T-27 was basically a two-man tankette armed with one DT 7.62 mm machine gun. Its production began in 1931, and by the time the production stopped in 1933, slightly fewer than 3,300 had been built (the precise number differs greatly between sources). Given their obsolescence, the T-27 did not stay long in active service, as it was replaced by much more modern tank designs. The T-27s were allocated for crew training, but during the Axis invasion of the Soviet Union in 1941, many would be put into service. They performed poorly due to their weak armament and armor.

T-27 in Soviet Service. Source: www.worldwarphotos

Improving Firepower

While the T-27 filled the gap of a lack of armored vehicles, its potential combat effectiveness was limited due to its weak armament and its general configuration which lacked a turret. As they were available in great numbers, discarding them was not a proper solution. On the other hand, increasing their overall combat performance by adding new armament was something that the Soviet Army considered doing.

For this reason, in October 1930, an official order was issued that such modification be implemented. The following year, a design team led by K.K. Sirken from the Leningrad Bolshevik, began the first steps to do exactly that. The overall T-27 design was to remain the same, with the exception of the vehicle’s right superstructure, where some modification would be required in order to fit the larger gun. This would lead to the creation of two prototypes. These received slightly different armament rearrangements. In addition, the first prototype used a four-wheel suspension, while the latter used the more common six-wheel suspension. Due to the rather short development time, this project appears to have received no official designation.



The hull of this vehicle could be divided into three compartments or sections. The front-mounted transmission with the drive unit, the central engine compartment, and the two fully enclosed crew positions (opposite of the engine).


The engine from this T-27 modification was unchanged. It was powered by a Ford four-cylinder petrol, water-cooled engine delivering 40 hp @ 2,200 rpm. The T-27’s maximum speed with this engine was around 35 km/h, while the operational range was 110 km and 60 km cross-country. The weight of this vehicle was 2.7 tonnes. The modified versions with the extra added weight likely had slightly worse overall driver performance.


The T-27 was used in two similar suspension configurations. One used the original 4 road wheels placed on a suspension cradle. In addition, there was a front drive sprocket and rear idler. The road wheels were placed in par on bogies which were suspended using simple flat leaf springs. The Soviets were not satisfied with this design, so they improved it by adding another pair of wheels.

The T-27’s suspension consisted of six road wheels, one front drive sprocket, and a rear-positioned idler. There was no return roller, instead, a simple guiding rod was used for the upper track section. Source:

The first prototype armed with the 37 mm gun used a four-wheel suspension. While there is very little information on these vehicles’ overall construction, thanks to surviving photographs, it is possible to identify that some structural changes were made. Given the recoil force of the gun, the integral structure of the suspension had to be strong. The part of the suspension cradle that held the rear idler was reinforced. Lastly, the upper track guiding rod was replaced with two simple return rollers.

The first attempt to modify a T-37 led to the use of a strengthened four-wheel suspension. Two small return rollers were used on this prototype, Source: A.G. Solyankin Отечественные бронированные машины.

This arrangement appears to have been insufficient for this modified vehicle. So, on the second prototype, a six-wheel suspension was used. It also received extensive structural improvement to better cope with the gun’s recoil. Its suspension cradle appears to have been slightly larger than on a standard T-27 vehicle. While the two upper return rollers remained, they appear to have received some kind of leaf spring addition.

The suspension on the second prototype was even further improved, in order to better cope with the new gun installation. Source: Svirin M. N. Самоходки Сталина. История советской САУ 1919-1945
Rear view of the modified T-27. Source:


The superstructure is another part of the vehicle that was heavily modified. Originally, the T-27 had a simple box shape superstructure that covered most parts of the vehicle. The crew’s head (and the engine’s top) were protected by a pyramidal-shaped hatch. In front of the crew compartment, there was a hatch placed on the upper glacis that provided access to their transmission unit. The T-27 was built using simple plates connected using bolts.

The driver and the gunner positions were protected by two pyramidal-shaped hatches Source: www.worldwarphotos

The right part of the superstructure, where the machine gun port was originally located, was redesigned in order to fit the larger gun inside of it. This part was greatly extended forward to provide room for the gun mount. Not much is detailed in the sources about this new superstructure’s design. We can assume though, that due to the T-27’s small size, it would be quite cramped and difficult for the gunner to operate this gun.

To accommodate the gun and provide the gunner with working space, the left side of the vehicle’s superstructure was enlarged. Note the trailer which was used to store additional ammunition. Source:,en/


The initial armament of the T-27 consisted of only one 7.62 mm DT machine gun. This proved to be completely inadequate and was the main reason why this project was initiated. Instead, the Soviet designers wanted to install a 37 mm gun. Two guns were initially considered: the PS-2 and the B-3. Due to delays in production, neither of them was available for use.

As a replacement, a 37 mm Hotchkiss which was in service by the Soviet Army was chosen instead. In the first prototype, this gun was placed in the enlarged gunner position. The overall construction and the general characteristic of this gun mounted on the modified T-27 are not specified in the sources. What is known is that the performance of this vehicle was poor. The chassis became overburdened with the added weight of the gun, ammunition, and extra armor. It was noted that the ammunition for the main gun took up too much space inside the vehicle. As a temporary solution, a trailer was to be used to transport additional ammunition.

The front view of the first prototype. Source:,en/

The second prototype received more modifications in order to provide more working room for the gun. The Soviet engineers were a bit overambitious, as they added a machine gun to this vehicle. For this reason, the main gun was placed in a lower position. Above it, a Degtyaryov 7.62 mm DT machine gun was placed on a ball mount. The machine gun could be operated independently of the main gun. In theory, this would provide armament to deal with the enemy armor and infantry. Realistically, this arrangement proved too much for the small vehicle and cumbersome to use.

The second prototype had its gun placed in the lower position. Above it, a machine gun ball mount was placed. Source:,en/


The crew consisted of only two: the commander/gunner and the driver. The driver’s position was on the left and the gunner was on the other side. This arrangement was not changed on the modified T-27. Interestingly, on the second prototype, the Soviets tested the use of dual controls, meaning that both crew members could drive should the need arise.

The small size of the T-27 is evident here. Source:


Given its slight weight and small size, the T-27 was only lightly protected. The armor thickness of the front armor was 9 mm, the side and rear were 8 mm thick, the bottom was 4 mm, and the top was 6 mm thick. There is no mention in the sources that the armor of the modified T-27 was changed. This level of protection ensured that the vehicle was protected against small arms fire and shell splinters, but little else.

Ultimate Fate

After a series of examinations, it quickly became obvious that this concept was flawed. The gun was simply too heavy for the chassis. The use of machine gun placed above the gun was difficult to operate. The added weight led to engine overheating problems. As a result, the project was rather quickly terminated. It is not clear if any additional vehicles were built beside the two already mentioned prototypes. Some sources, such as D. Nešić (Naoružanje Drugog Svetsko Rata-SSSR) mention that a small production run was made.

Despite the cancellation of this project, the experimenting with stronger armament on the T-27 continued. An installation of a recoilless gun on the right side of the vehicle was tested. In addition, a modified version with a 76.2 cm gun installed to the vehicle’s rear was also built. None of these entered productions and any further work on improving the armament of the T-27 was discontinued.

A prototype armed with a recoilless gun. Source:
Mounting an infantry support gun on the T-27 also proved futile. Source:


While the whole concept of rearming the older design with a stronger gun was sound, in reality, this was impossible to achieve. The T-27’s chassis was simply too small and weak. The 37 mm armed T-27 project was essentially doomed from the start. The gun weight and its recoil were probably too much for the small chassis. In addition, the working space inside it was quite limited to effectively operate this gun. This ultimately led to the cancellation of this project, but at least, it offered some experience to the Soviet tank engineers.

The first modified T-37 used a strengthened four-wheel suspension. Illustration made by Godzila.
T-27 37 mm second prototype The suspension was further improved, in order to better cope with the new gun installation. In addition, an installation of a machine gun was tested.  Illustration made by Godzila.

T-27 with the 37 mm gun Technical specification

Crew Commander/Gunner, and Driver
Weight over 2.7 tonnes
Dimensions Length 2.65 m, Width 1.83 m, Height 1.47 m
Engine 44 hp Ford petrol engine
Speed 45 km/h
Primary Armament 37 mm gun
Secondary Armament One 7.62 mm DT machine gun (second prototype)
Armor 6 to 9 mm


S. J. Zaloga and J. Grandsen (1984) Soviet Tanks and Combat Vehicle of World War Two, Lionel Leventhal
T. Bean and W. Fowler (2002) Russian Tanks Of World War II MBI Publishing Company
Svirin M. N. (2008) Самоходки Сталина. История советской САУ 1919-1945, Эксмо
A.G. Solyankin (2002) Отечественные бронированные машины. XX век Том 1, Цейхгауз
D. Nešić, (2008), Naoružanje Drugog Svetsko Rata-SSSR, Beograd,en/

WW2 Soviet Prototypes

T-150 (KV-150/Object 150)

Soviet Union (1940-1943)
Heavy Tank – 1 Prototype Built

The KV-150, or more commonly named T-150, was an attempt to improve the armor of the KV-1 even before the KV-1 entered mass production. With 90 mm of armor all around and a 700 hp engine, it could have been a better option had it not been for some critical events during its development phase. It was, however, groundbreaking in what would become a series of KV heavy tanks, and the single prototype saw combat service until the end of 1943.

The KV-1

As one of the most iconic and recognizable tanks of the Second World War, the KV-1 (or simply KV, acronym for the People’s Commissar of Defense for the Soviet Union, Kliment Voroshilov), proved to have unmatched armor and a very potent gun at the start of the German invasion of the Soviet Union, on 22 June, 1941. It had been developed in the late 1930s and tested in combat alongside its 2 much larger competitors, the SMK and T-100, during the Winter War. As the latter 2 followed a much more complex and archaic breakthrough tank philosophy, namely multi-turreted “landships”, the KV-1 (at the time U-0) would be selected for further development. It was created at the Kirov Leningrad Plant (LKZ), where the previous T-28 and its own competitor, the SMK, were designed and built.

By 19 December, 1939, production of 50 KVs was ordered, with mass production to begin in 1941. But, during this time, the ugly side of the vehicle started to come to light. Truth is that, by that time, the KV was far from ready for production, and dozens of mechanical problems, mostly caused by the heavy weight, had to be sorted out. However, due to Stalin’s personal involvement and pressure on the project, the KV entered preseries production in February 1940, which were indexed with a “U” prefix. These differed from vehicle to vehicle and were tested thoroughly to diagnose any issues.

The first KV, the U-0, which would be tested in combat on the Karelian Isthmus in December, 1939.
Source: Topwar

Naturally, Stalin’s patience would not last, and in June 1940, in what would be called “The Stalin Task”, a decree from the Council of People’s Commissars of the Soviet Union would increase the yearly production quota of the KV to 230 units of both variants (130 standard KV-1 and 100 KV-2s with 152 mm howitzers). This immediate increase in production strained the LKZ plant into mass producing what was effectively an unfinished tank. Naturally, corners and compromises had to be cut over all fields in order to streamline production and cut costs. As some KVs were built, others were still vigorously tested, and results showed that the reliability of the gearbox and transmission were poor. Although changes were made, this aspect would become the bane of the KV-1’s existence. From February to July, 32 KV tanks had been built, and production would increase to 20 during the month of August and 32 during September.

A KV-1 built during August or September 1940, abandoned during early stages of the Great Patriotic War. It is armed with the 76 mm L-11 gun.

More Armor

As early as May 1940, before the KV-1 even entered its shy mass production, the topic of improving the armor of the KV was discussed both by the GABTU (Main Directorate of Armored Forces) and by the People’s Commissariat of Heavy Engineering, where the LKZ plant was represented at. First mentions of thickening the KV tank’s armor came on 11 June, which claimed the need to up-armor the tank to armor between 90 and 100 mm. Furthermore, on 17 July, 1940, the Council of People’s Commissars of the Soviet Union adopted decree No. 1288-495cc, which stated:

  • By November 1, 1940, the Kirov Plant will produce two KV tanks with 90 mm of armor: one with a 76 mm F-32 gun, the other with an 85 mm gun. The Izhora Plant will deliver one hull at the end of October, the production of the tank is scheduled to be completed by November 5. The second hull will be made by November 5th.
  • By December 1, 1940, the Kirov Plant will produce two KV tanks with 100 mm of armor: one with a 76 mm F-32 gun, the other with a 85 mm gun. One hull will be delivered by the end of October and by the end in November.

In comparison to its predecessor, the KV-1, as being built in summer-autumn 1940, had 90 mm around the gun mantlet and 75 mm all around. These were exquisite levels of armor not just for Soviet tank standards, but also internationally, being able to withstand most anti-tank guns. It also put the weight of the KV at 44 tonnes, already a tonne increase from the U-0. The weight of the KV would keep on increasing, peaking at 47.5 tonnes by 1941.

Regarding the armament mentioned in the decree, the KV-1 was equipped, as a stopgap measure, with the L-11 76 mm gun until mass production of the more potent 76 mm F-32 could begin. As for the 85 mm gun, it was likely to be the F-30 gun developed by V.G. Grabin at plant No. 92 in Gorky, based on the 85 mm M1939 52-K. However, it is noteworthy that only one such gun had been built, and its testing had yet to conclude.

The first obstacle that the up-armored KV faced was the KV itself. By July, the design bureau tasked with its development, SKB-2 and the entire LKZ factory were busy producing and improving the KV, with little room to spare for a new development. The situation was worsened by the delayed delivery of the tank requirements from the military to SKB-2.

Joseph Yakvolevich Kotin, head of SKB-2’s design bureau and one of the greatest heavy tank designers of the Soviet Union.
Source: Andrei BT

In August, head of the SKB-2’s design bureau, J.Y. Kotin, made two teams for the development of the two tanks. The 90 mm-armor KV was to be designed by a team led by Military Engineer L.N. Pereverzev and indexed as T-150 or Object 150 / KV-150. All 3 names were used in documents. For the sake of simplicity and consistency, it will be called T-150 in the article, with the exception of direct document translations. At this point, Pereverzev was still rather new to SKB-2, having just graduated from the Military Academy of Mechanization and Motorisation of the Red Army in 1939, and had only worked on the KV-1.

After the start of WWII, being a military officer, Leonid Nikolevich Pereverzev was put in charge of the 22nd Mobile Repair Battalion, dispatched from LKZ, focusing on KV tanks. By the end of the war, he had received a variety of medals and orders for his efforts during the war. In his short tank design career, he had worked on the KV-1, T-150, T-220, KV-3, and KV-4.
Source: Yuri Pasholok

For designing the 100 mm-armored KV, the more experienced L.E. Sychev was appointed as chief designer. This variant would be indexed T-220 or Object 220 / KV-220. Sychev was a tank design veteran. He had worked on his bachelors at SKB-2 and then began his career in the same place, working on the T-28, SMK, and KV-1.

Once SKB-2 had sent over the documents (likely in September 1940) to the Izhora plant, the T-150 faced another issue. The Izhora plant was working at a very high capacity trying to increase its KV tank output. The 4 prototype KVs were to be built at Hall No.2, where 4 KV tanks were already being built at the same time. This meant that the October 1 deadline for the T-150 was missed, but not by much.

The Izhora plant delivered the hull of the T-150 and a turret on November 1 and LKZ completed the prototype by December. The T-220 was completed shortly after.

The T-150 after it was completed (December-January). Externally, it looked like a KV-1, with the main difference being the commander’s cupola.
Source: Warspot, colorized by Johannes Dorn

In November, during the latter stages of the development of the T-150, a new turret was proposed. It moved the commander to the rear of the turret and gave him a low cupola with a PTC rotating periscope. Other aspects remained the same as on the original T-150 turret. Only a simple sketch of it was done, with a slightly more detailed drawing of the new commander’s position. It was not considered, but it was used as the basis of the Object 222’s turret, which was essentially the T-150 with a completely new turret .

The November 1940 sketch for an improved turret for the T-150.
Source: Warspot
New commander’s position on the proposed turret. It was never considered for production but served as the basis for the one on the Object 222.
Source: Warspot

Object 221 – The T-150’s Bigger Brother

As per the request from 17 July, 1940, two tanks were supposed to be built with 90 mm armor, one with a 76 mm gun and one with an 85 mm gun. The first became the T-150, however, the latter had a more troubled development. When researching about the mounting of a 85 mm gun on the chassis of the KV-1, it was realized that it would not fit in the standard KV turret and a larger turret combined with additional armor would require a longer hull. This meant that both the 90 mm and 100 mm variants armed with an 85 mm gun would receive a longer hull, by one roadwheel (a total of seven). The 100 mm armored variant armed with the 85 mm gun became the T-220.

The 90 mm variant was named Object 221 or T-221. It was intended to mount the same turret and 85 mm F-30 gun as the T-220. However, there were serious delays, and the Izhora plant only managed to deliver hull components for the T-221 by 10 February 1941, and the F-30 gun and turret were not ready. On 19 February, Marshall of the Soviet Union G.I. Kulik proposed that the 76 mm F-27 gun be mounted inside a KV-1 turret instead, but nothing was done. The Object 221 remained abandoned until April, when it was used as the basis for the KV-3 (Object 223), though 30 mm of extra frontal armor were required for it to reach the specified armor thickness.


For the most part, the T-150 was identical to the KV-1. As the additional 15 mm of armor were added on the outside of the hull, the internal layout for the crew was unchanged. The main armament was, as requested, a 76.2 mm F-32 gun, coaxially paired with a 7.62 mm DT machine gun to the right of the main gun, with another DT machine gun at the rear of the turret and one in the hull, next to the driver. Both machine guns were mounted in ball mounts.

The weight of the T-150 reached 50.16 tonnes, around 6 tonnes heavier than a KV, and went past the weight threshold by over 2 tonnes. Due to the increased weight, the suspension was reinforced. Otherwise, the hull remained identical to that of the KV-1, with front idler, large rear sprocket and 6 steel-rimmed roadwheels.

The front of the tank had the same features as the KV-1, with 2 tow hooks on the lower plate, a single driver viewport in the center of the upper plate, with a driving light to its right and ball mounted machine gun to its left.

The turret was essentially a KV-1 turret with thicker armor, but certain changes were made to accommodate the commander’s cupola. It was fixed in place and of cast construction. At the front, a fully rotating PTC periscope was mounted, with 6 other triplex periscopes around the cupola. The commander’s cupola likely lacked a service hatch, meaning that the commander and loader would likely have to share a hatch. The turret also featured the standard KV-1 vision devices, a PTC rotating periscope for the gunner and another periscope to the side and 2 facing the rear. Direct vision slits were provided over the machine gun ports. This meant that, on paper, the T-150 offered better vision for the crew than the KV-1. The driver’s vision systems were not changed.

The main novelty of the T-150 was its 90 mm armor all around the turret and hull. The turret deck, hull deck and hull belly were 30-40 mm thick. The commander’s cupola was rather large, but was also 90 mm all around and, thus, was not a weak spot. Frontally, this was a 20% increase in raw thickness over the KV-1 in most areas.

Side view of the T-150. The tarpaulin on the fender was used to cover the turret and gun during trials.
Source: Warspot


The crew of the T-150 was the same as that on the KV-1, with 5 men: driver, radio operator/bow machine gunner, commander, gunner, and loader.

The commander was seated to the right of the gun, where he would be able to observe the battlefield from his cupola. He was also tasked with loading the coaxial DT machine gun on his side. The gunner sat on the other side of the gun, to the left of the turret. He would aim and fire the gun via a TOD sight. He had a rotating PTC and fixed periscope for external vision. He was able to rotate the turret via an electric system but also with a hand crank. Behind the commander sat the loader, on a removable seat (for easier maintenance/loading). He would load the main gun with shells stored on the side turret walls and in cases on the hull floor. He would also operate the rare turret machine gun, should the situation require.

In the center of the hull sat the driver, and to his left the radio operator, who also manned the bow DT machine gun. The radio was mounted underneath the frontal plate.

Engine and Propulsion

The engine installed on the T-150 (and T-220) was the four-stroke V-5 diesel, 12-cylinder in V-config with an output of 700 hp. It was essentially a boosted V-2K (600 hp), which itself was a boosted variant of the V-2. The main problem was that the V-2K was unreliable and barely guaranteed to work for up to 100 hours. Consequently, the V-5 was even less reliable. So much so that, during trials, the chief designer from Plant No.75 could not guarantee the function of the engines on the T-150 and T-220. Combined with the poor design of the engine’s cooling system done by SKB-2 engineers, the engine would have several major issues during the trials and only worked for 199 km, or 24 hours.

The fuel tank capacity remained the same as on the KV-1, at 615 liters, which reduced the range to 220 km (on roads).

Rear of the T-150 tank.
Source: Warspot


The main armament on the T-150 was the 76.2 mm F-32 gun. It was developed by Plant No.92 in Gorky in the late 1930s and was tested on the BT-7. It could fire BR-350A and BR-350B (APHE), BR-350SP (AP), and OF-350M (HE). The shell weight varied between 6.2 kg and 6.78 kg, depending on the type. The muzzle velocity was between 613 and 621 m/s (figures vary depending on the source consulted). In January 1941, the KV-1 would enter production with the F-32 gun. It was ballistically very similar to the L-11 it was replacing on the KV-1, while the T-34 would receive the far more potent F-34 76 mm gun the same year.

76 mm F-32 gun, used on the T-150
Source: Sovietarmyforum via Rotor

For proximity and anti-infantry defense, three 7.62 mm DT machine guns were mounted, one coaxially, to the right of the gun, which could be used for ranging closer targets (muzzle velocity around 840 m/s). The front facing machine gun in the bow was for suppression of infantry and the machine gun in the rear of the turret was for defense against flanking infantry.


On 14 January 1941, the People’s Commissariats of Defence and People’s Commissariats of Heavy Engineering requested that the T-150 and T-220 be tested at the LKZ proving grounds. A commission, headed by the Military Engineer 1st Rank Glukhov and with representatives from the GABTU, would monitor the testing of the tanks. According to the commission for field testing, the following goals were intended.

  • Determining the tactical and technical characteristics of the tank.
  • Identifying the shortcomings in the designs and their elimination prior to mass production.
  • Judging whether it is possible to conduct military tests.
  • Accumulating data for operating and repairing the tanks.

The T-220 during its trials. It was developed alongside the T-150 from the original request for a KV tank with 100 mm of armor and 85 mm gun.
Source: Tank Archives, colorized by Johannes Dorn

The tests would begin the following day on both tanks. During this time, several issues were quickly identified. On 25 January, the two prototype tanks were weighed, with the T-150 weighing 50,160 kg and the T-220, 62,700 kg. The problem here was that the GABTU specifically requested the T-150 to weigh a maximum of 48 tonnes and the T-220 56 tonnes. A report written by Military Engineer 1st Rank Glukhov on 28 January to the Head of Armored Department of the GABTU, Military Engineer 1st Rank Korobov, in the midst of the trials, showed that the commander’s cupola was poorly made (the observation devices were located too high, vision was inconvenient) and was placed in the loader’s position, who is not in command of the tank. Comically, the Chief Designer of Plant No.75, T. Chuptakhin, who was present at the trials, was not able to guarantee the operation of the engines installed on the T-150 and T-220 tanks. One of Glukhov’s reports included the following passage:

“The T-150 tank, after replacing the engine that failed during the factory run on 21 January, has not yet been brought back to the accepted state required by the Quality Control Department and military representatives.”

The gunshield was crudely made and provides only 3º of gun depression, instead of the 6.5º, as specified by the drawings.”

Due to the breakdown of the experimental V-5 engine provided by Factory No.75, the T-150 traveled only 199 km, or 24 work hours. Several issues were found and once again reported by Glukhov:

The engine’s oil cooling system prevents the tank from driving at high speeds in the 3rd and 4th gear (at an outside temperature of 9° to 12°, the temperature of the injected engine oil increased rapidly after 5 minutes of motion in 3rd and 4th gears). Normal operation of the engine (inlet oil temp. 70°-80°). Due to the poor design of the cooling system, driving trials on the T-150 would cease.”

The T-150 (left) hooked up to the T-220 (right) during trials.

Instead, focus shifted towards firing trials, especially relevant as the F-32 gun had just replaced the L-11 gun on the KV-1’s production lines. Firing while stationary and firing during short stops went as expected (considering the 4-5 second aiming time), but firing on the move was unsatisfactory, though many of these results were entirely based on circumstances such as terrain and gunner skill, and the gunner conducting the trials, although experienced, was still not entirely familiar with the gun and tank.

Simultaneously, loading times were measured, depending on where the rounds were stowed. When loading shells from the right turret side (9 rounds), 5-7 rounds per minute were sustained. When loading shells from the left side of the turret (9 rounds), the rate of fire dropped to 3 rounds per minute, as the loader had to lean to the other side of the turret. The situation got worse when loading via casings that held 3 rounds. These would have to be lifted up and opened before the shells could be loaded in. This process slowed the rate of fire to 1-2 rounds per minute. In contrast, although not practical, when the shells were simply laid on the floor, 11 rounds per minute could be sustained. Furthermore, the ammunition cases, stowed on the hull floor, would often catch on one another when attempting to lift them, and on 6 separate instances, rounds were jammed inside. The sharp edges of the cases also injured the loader’s hands. Consequently, the commission noted that the ammunition stowage system had to be reworked.

Several issues had been noted with the crew’s positions as well. Firstly, the commander’s seat (combined with the cupola) were criticized for being fixed in place, preventing the commander from viewing out of the periscopes while seated. Likewise, he could not stand, as there was no room, but rather the commander had to stand with his knees slightly bent, in a semi-squatting position (naturally very tiring) to see out of the cupola. Other complaints included that he had to turn very frequently to communicate to the rest of the crew and he was also charged with loading the coaxial DT machine gun.

The gunner’s position also required improvements. The sight was deemed too far forward and slightly to the left, and the seat required more adjustment. The footrests and pedals required work as well. The knee would be bent too much. Additionally, the heel rest was too far down, requiring the gunner to keep his heel in the air in order to maintain his toes on the pedal, or overextend his ankle, both very tedious tasks.

The loader, aside from the aforementioned loading problems, would have his workspace cramped up by the commander’s seat, only 6-8 ammunition cases were easily accessible, and the machine gun drums were in the way when lifting rounds from the left turret wall.

T-150 after trials, February 1941. The background was manually ‘erased’.
Source: Warspot

Testing of the T-150 was concluded on 14 February. The trial results were reported back to the GABTU and People’s Commissariat of Heavy Engineering. Although the aforementioned issues were noted (and such problems were understandable for a prototype vehicle), it was decided to move forwards with the T-150 project, but in an altered form. Based on reports during this time, both the T-150 and T-220 were sometimes called KV-3. The more common use of this name came with the Object 222 and later with the Object 223, the KV-3 commonly known today.

On 21 February, a commission was made for analyzing the reason for the failure of Plant No.75’s engines on both the T-150 and T-220, and estimating a time of arrival of the fixed engines. The deadline was set for 10 April.

During the same period, between 18 and 24 February, Plant No.75 tested the V-5 engine on KV tank U-21, and it broke down once again, after 40 hours of operation.

On 1 March, the T-150 was officially canceled. The V-5 engine was still unrefined, and the tank was deemed to have several issues necessary to fix, but there was no point in doing so. Instead focus was shifted to the Object 222, which was based on the T-150.

Object 222

Many of the issues of the T-150 that were discovered during the factory trials were identified far earlier on. As a result, the SKB-2’s design bureau started work on a new tank in January-February, 1941 to fix these issues. The new tank, which used the same hull as the T-150, would be indexed Object 222. Originally, the differences between it and its predecessor consisted of a new cooling system and a new turret. This new turret was slightly larger, had flat sides (as opposed to 15° angled inwards on the KV-1 and T-150), and a slightly sloped frontal plate. The commander and his cupola were moved to the back of the turret as well.

By the end of February, the People’s Commissariat of Defence and the Central Committee of the Communist Party proposed accepting the KV-3 (Object 222) into service. Additionally, the topic of improving the main armament to the 76.2 mm F-34 was also raised. This gun had improved ballistics over the previous F-32 on the T-150. As for the propulsion, the tank was to use the same V-5 engine.

On 3 March 1941, a commission was formed, consisting of Military Engineers 2nd Rank I.A. Burtsev and I.A. Shpitanov, Military Engineer 3rd Rank Kaulin, LKZ Director I.M. Zaltsman, SKB-2 Director J.Y. Kotin, Director of LKZ 1st Dept. A.Y. Lantsberg, and NII-48 research institute engineers V. Dalle and A.P. Goryachev. Together, they reviewed the drawings and a full-scale wooden mock-up turret of the Object 222 turret mounted on a KV-1 (for simplicity’s sake). Turret armor would have been 90 mm all around and 40 mm on top. Several issues were identified, such as the flat turret walls, which were deemed to decrease protection, the less than ideal commander position, and the lack of hatch on the cupola for the commander. Despite these issues, the commission concluded that the turret should be built anyways, since there was little time to redesign it.

On March 15, the Council of People’s Commissars of the Soviet Union and the Central Committee of the Communist Party gave decree No. 548-232§, which imposed that LKZ had to switch mass production to the KV-3 (Object 222) in June.

The officials were confident that, by then, the new turret could be tested and refined. As for the T-150’s hull, with the new cooling system and properly tuned V-5 engine, it would run smoothly, as it was essentially just an up-armored KV-1 hull.

Object 222 drawings, circa March 1941. The tank was named KV-3 and was supposed to enter service in June, but the situation changed shortly after. It used the hull of the T-150.
Source: Yuri Pasholok

German Heavy Tanks

However, 4 days earlier, on 11 March, the Soviet Intelligence services had just released a report regarding the German Reich’s tank developments. Notes of several heavy tanks were highlighted, notably three new tanks that were under development. One of them was labeled Mark V, was to weigh 36 tonnes, and be armed with a 75 mm gun. The Mark VI was to weigh 45 tonnes and be armed with a 75 mm gun, and, finally, the Mark VII was to weigh 90 tonnes and be armed with a 105 mm. The first 2 tanks can be confidently identified now as the VK.30.01(H) and VK.36.01(H) and early Tiger mentions. But the latter can only be described as some early proposal to what would become the Pz.Kpfw.VII Löwe, which was first mentioned officially in German documents in November 1941.

This new German heavy tank was nearly double in weight of the KV-3 and considerably above the T-220. The 105 mm gun was far more alarming than the 76.2 mm F-34 that the KV-3 (Object 222) was to be equipped with and the 85 mm F-30 on the T-220.

On 21 March, the GABTU requested the urgent development of a new heavy tank from SKB-2 at LKZ, capable of matching the supposed German heavy tanks. It was to weigh up to 72 tonnes, have 130 mm of frontal armor, and be armed with the 107 mm ZiS-6 gun. It was indexed Object 224 / KV-4. On April 7, the GABTU would rework their approach, requesting that the KV-3 be based on the T-220 (Object 220) and armed with a 107 mm ZiS-6 and weigh 68 tonnes. The new KV-3 was indexed Object 223. An even heavier tank was also conceived, the KV-5 (Object 225), with 170 mm of frontal armor and 150 mm of side and rear armor, weighing over 100 tonnes.

The ‘later’ KV-3 (Object 223) with the 107 mm ZiS-6 gun. Development would start in April, based on the Object 221, and would continue until December 1941.
Source: Warspot

After the invasion of the Soviet Union and the Siege of Leningrad in September, much of the SKB-2’s design bureau and its prototype tanks were evacuated to the ChTZ plant in Chelyabinsk, which was now renamed ChKZ, or Tankograd.

Most of the work on the heavy tanks was stopped in order to focus on more sensible topics at ChKZ. The only exception was the Object 222 (which had now been renamed to KV-6) and the Object 223 (KV-3). The GABTU was against the KV-6 and insisted on improving the armor of the T-150 to 120 mm and adding a new ZiS-5 gun. These were the last efforts on these tanks. The Object 223 (KV-3) progressed until December 1941.

These experimental tanks were incredibly expensive. A letter sent on 30 May 1941 to Military Engineer 1st Rank Korobov by A.Y. Lantsberg described the development costs of the major KV series of heavy tanks (Object 150, Object 220, Object 221, Object 212, Object 218, Object 223, Object 224, and Object 225). These had a total development sum of 5,350,000 rubles. The T-150 project would cost in total 1,500,000 rubles. In perspective, a KV-1 in 1941 would cost between 523,000 to 635,000 rubles.

Stage of T-150 Development Price (thousands of rubles)
Draft drawings 50
Technical drawings 50
Prototype construction and factory trials 900
Proving ground trials 100
Drawing correction after trials 25
Repair of prototypes and improvements 375
Total cost 1500

Source: CAMO RF 38-11355-101

One of the more sensible alternatives was the KV-1E (the E is a post-war addition and derives from the Russian word meaning shield or screens), a regular production KV-1 with 30 mm to 25 mm additional armor plates, making the protection of the KV-1E superior to that of the T-150. The idea of the KV-1 with appliqué armor appeared on 19 June, 1941 and would be given to troops by July.

KV-1 with appliqué armor knocked out. The additional armor on the side of the hull and turret can be seen.
Source: World War photos

Second trials

The work on Object 222, Object 223, Object 224, and Object 225 tanks did not mark the end of the T-150 prototype’s career. During the month of June 1941, the T-150 was retested with a worked-out V-5 engine and improved cooling system. This time, it traveled 2,237 km by 19 June. In total, 5 different V-5 engines had been installed on the tank during its trials. Amongst the issues noted were:

Oil leaks from the gearbox’s primary oil retainer.
Teeth from the 3rd and 4th gear as well as conical gear were sheared off.
Collar bracket of the 2nd and 4th gears were worn out by 4 mm.
2 rubber shock absorbers had been destroyed.
Paper fuel filters failed

Several new production methods had also worked well, such as hot-pressing the torsion bar with the torsion arm together, and the gearbox casing, made out of recycled aluminium, did not show sign of damage or failures after 1671 km.

T-150 in Combat

As the Soviet Union was suffering rapid defeats against the Axis powers, prototype tanks were pressed into service. The T-150 would be no exception. It entered service with the 123rd Tank Brigade on 11 October 1941. A week later, on 18 October, the brigade, part of the 8th Army, fought around Neva Dubrovka and later crossed the Neva river. On 18 May 1943, the T-150, by then part of the 31st Guards Heavy Tank Regiment, was listed as knocked out beyond repair. But the need for tanks was there and it was sent to Plant No.371 for repairs and entered service with the same regiment in July. The commander was Guards Junior Lieutenant I.A. Kuksin and driver-mechanic was Technician-Lieutenant M.I. Shinalsky and the tank received the number 220 and callsign “Som” (Catfish).

Shortly after, Kuksin’s tank would partake in the Mga Offensive or Third Battle of Lake Ladova, and on 22 July 1943, the 31st Guards Heavy Tank Regiment, alongside 63rd Guards Rifle Division, engaged enemy forces south-east of Leningrad. During the fighting between July 22 and August 6, the 31st Guards Heavy Tank Regiment recorded kills of 10 enemy tanks (allegedly 5 Tiger tanks, 3 Panzer IVs, and 2 Panzer IIIs), 10 pillboxes, 34 foxholes, and 750 enemy personnel. Kuksin’s T-150 and his crew also performed well. During this period, they recorded the destruction of 5 foxholes, 2 light machine gun posts destroyed, and 36 soldiers. Their tank was also hit in the track and immobilized, yet the crew managed to get the track together and continue fighting. The tank held its position for 4 days, for which Kuksin and his crew received the Order of the Red Star.

KV-1 with number 207 during maintenance and another KV conducting track repair. According to Yuri Pasholok, these belonged to the 31st Guards Heavy Tank Regiment and the photo was taken in late July 1943. The tank with the track being repaired is claimed to be the T-150 itself.
Source: Warspot

On 12 August, the Regiment was assigned, with the 73rd Marine Rifle brigade, to capture the village of Anenskoye. The 1st and 4th companies attacked on 18 August at 04:55. The companies suffered heavy losses and, by 06:00, 9 out of the 10 tanks were taken out of battle, with only tank 206 being in working order. Amongst these casulties suffered on that day, the T-150 was one of them. Junior Lieutenant I.A. Kuksin, gunner Senior Sergeant A.S. Yurdin, driver Technician-Lieutenant M.I. Shinalsky, and loader Guards Seargant I.M. Brezhak were killed in action on 18 August and the T-150 was sent back to Plant No.371 for repairs.

Commander of the T-150, Junior Lieutenant I.A. Kuksin (left) and Guards Seargant I.M. Brezhak (right).
Source: Yuri Pasholok

Alternatively, a document dated 18 November 1943 shows that a new driver was assigned to the T-150 (noted as KV No.T-150, raising the question as to if the T-150 was ever given number “220”), and was still commanded by Kuksin.

It is worth highlighting that the T-220 also saw combat service, but its new turret and 85 mm F-30 gun were replaced with a regular KV-1 turret. The tank was knocked out during the defense of Leningrad.


The T-150 (KV-150 / Object 150) was, on paper, a minor upgrade to the KV-1, with just 15 mm of additional frontal armor, a more powerful 700 hp engine, and a new commander’s cupola. While the implementation of these changes proved problematic at first, the T-150 proved to be a very important step towards the design of even larger and heavier KV tanks. These ultimately proved to be a waste of money, time, and resources, assets which the Soviet tank industry did not have, especially with the Axis invasion. Like many Soviet pre-war prototypes and its larger brother, the T-220, the T-150 prototype saw combat service well into 1943, but what happened after is unknown.

T-150. Illustration by Pavel Alexe.
Object 222. Illustration by Pavel Alexe.

T-150 / KV-150 / Object 150 Specifications

Dimensions (L-W-H) (approx.) 6.76 x 3.33 x 3.01 m
Total weight, battle-ready 50.16 tonnes
Crew 5 (Commander, gunner, loader, driver, radio operator)
Propulsion V-5 12-cylinder diesel, outputting 700 hp.
Speed 35 km/h
Suspension Torsion bar, 6
Armament 76.2 mm F-32
3x 7.62 mm DT machine guns
Armor Front/sides/rear of hull and turret: 90 mm
Top/Belly: 30 to 40 mm
No. Built 1 prototype built and saw service


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. ( – S.I. Pudovkin
Yuriy Pasholok. HF Small Upgrade – Alternate History ( – Yuri Pasholok
Малая модернизация КВ | – Yuri Pasholok
КВ-3: набор танковой массы | – Yuri Pasholok
Опытный танк с боевой биографией | – 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 ( – Kirill Shishkin
Heavyweight tanks KV-3, KV-4, KV-5 (

WW2 Soviet Prototypes


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.

The IS-M model as represented in Wargaming’s game World of Tanks
Source: World of Tanks

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.

N.F. Shashmurin in the 1930s.

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.

IS-2 during testing at NIBT, January/February 1944. Note the 122 mm D-25T gun with the German-style muzzle brake.
Source: Warspot
The NiBT proving grounds’ proposal to change the shape of the frontal armor of the IS. Note the old shape in the non-continuous line.
Source: Yuri Pasholok
IS-2 with sloped frontal plate, as originally proposed by NiBT proving grounds and Shashmurin in 1944. The sloping is similar to that on the IS-M.

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.

Model of the second K tank (K-2) designed at SKB-2 in late 1943/early 1944 as a replacement for the IS-2.
Source: Heavy Tank IS-4

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.

The Object 701-0, the first prototype of what would become the IS-4.
Source: Supertanki Stalina IS-7

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.

Factory No.100 April design of an upgraded IS-2. Note the UFO-shape hull and large road wheels.
Source: Supertanki Stalina IS-7
The 2 models designed by Factory No.100 on either side of an IS-2 tank model.
Source: Warspot

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.


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.

Original drawing of the IS-M from an old magazine. The caption said “Breakthrough tank IS-M”. Note the SPG in the background, explained below.
Source: Warspot


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.


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.


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.


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
ISU-152-1 (Object 246) armed with the 152 mm BL-8 gun.
Source: Wikimedia


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.

Frontal cutout view of the IS-M highlighting the hull armor and engine placement.
Source: Screenshot from original drawing


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.

Full drawing of the IS-M variant with standard IS road wheels and return rollers.
Source: Screenshot from original drawing

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.

View of the IS-M based SPG. Note the much larger muzzle brake, characteristic of the BL-8.
Source: Screenshot from original drawing

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.

The modified Object 244 with 5 of the large-diameter road wheels and the 122 mm D-30 gun. Note the original IS road wheel in front of the sprocket.
Source: thedailybounce
Cutout drawings of the large-diameter roadwheel of the IS-6 (Object 252). They were originally designed for the IS-M.
Source: Warspot
The Object 252 IS-6 prototype during testing in November/December 1944. Despite being promising, its protection was deemed insufficient.
Source: Topwar

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 Kirovets-1 (not to be confused with the K-tanks), winter 1944.
Source: Warspot

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-2U designed at Factory No.100, was essentially an IS-2 with a new turret and frontal hull. It was the last significant attempt to modernize the IS-2.
Source: ofis7andthings

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.”

—N.F. Shashmurin, extract from Soviet Warrior magazine, interview by Sergey Ptichkin

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.


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 as illustrated by Pavel Alexe, funded by our Patreon campaign.
IS-M variant with standard IS road wheels and return rollers as illustrated by Pavel Alexe, funded by our Patreon campaign.
IS-M based SPG as illustrated by Pavel Alexe, funded by our Patreon campaign.

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


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 ( – 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 | – Yuri Pasholok
Not in the amplitude of the | -Yuri Pasholok
Muzzle wedge for heavy tank | Yuriy Pasholok | Zen ( – Yuri Pasholok
Tank Archives: Improving the IS-2 – Peter Samsonov
“>Russian Heavy Tank Object 244 – The Original IS-3 ( -Harkonnen
IS-2Sh – unusual “Stalin” (

Has Own Video WW2 Soviet Prototypes


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

One of the most recognizable tanks of the Third Reich was the Panzerkampfwagen V “Panther”. Created as a replacement for the medium Panzer III and Panzer IV tanks and as a “response” to the Soviet KV and T-34, the Panther was a formidable opponent on the battlefield. A powerful and rapid-firing gun, good aiming devices for the crew, and strong frontal armor made the vehicle excellent in both defensive and offensive operations. Panthers captured by the Red Army were highly valued. During the war, Soviet troops captured a significant number of serviceable or damaged, but recoverable Pz.Kpfw.Vs, and even combat units of the Red Army were created on their basis. The option of rearming them with “domestic” guns was also considered, however, the T-V-85 appeared too late, and the end of the war left it no chance of appearing in reality.

The Medium Cat of the Wehrmacht

The first considerations for a new medium tank which could replace the Panzer III and Panzer IV appeared in 1938, with the VK20 project series, a fully tracked vehicle weighing ~20 tonnes. Design proposals by Daimler Benz, Krupp, and MAN ensued, but soon, these designs were abandoned and Krupp dropped out of the competition entirely. The requirements increased to a vehicle weighing 30 tonnes as a reaction to the encounters with the Soviet T-34 and KV-1 tanks.
At the insistence of General Heinz Guderian, a special tank commission was created to assess the T-34. Among the features of the Soviet tank considered most significant were the sloping armor, which gave much improved shot deflection and also increased the effective armor thickness against penetration that could be achieved with thinner plates, the wide tracks, which improved mobility over soft ground; and the 76 mm gun, which had good armor penetration and also fired an effective high-explosive round. All this outclassed the existing models of the German Panzer III and IV. Daimler-Benz (DB), which had designed the successful Panzer III and StuG III, and Maschinenfabrik Augsburg-Nürnberg AG (MAN) were given the task of designing a new 30- to 35-tonne tank, designated VK 30, by April 1942.
MAN’s design won the competition, despite DB’s one having several advantages and having the admiration of the Reich’s Ministers for Armaments and Munitions, Fritz Todd and his successor, Albert Speer. One of the principal reasons given for this decision was that the MAN design used an existing turret designed by Rheinmetall-Borsig, while the DB design would have required a brand new turret and engine to be designed and produced, delaying the mass production of the vehicle.

Pz.Kpfw.V Panther Ausf. G external appearance.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The initial production target was 250 tanks per month at the MAN plant at Nuremberg. The first production Panther tanks were designated Panther Ausf.D, not Ausf.A. Later production targets were increased to 600 per month in January 1943. Despite determined efforts, this figure was never reached due to disruption by Allied bombing, and manufacturing and resource bottlenecks. Production in 1943 averaged 148 tanks per month. In 1944, it averaged 315 a month, with 3,777 built throughout the year. Monthly production peaked at 380 in July 1944. Production ended around the end of March 1945, with at least 6,000 built in total. A Panther tank cost 117,100 Reichsmark (~US$60 mln in 2022) to produce.

Panther in Soviet Use

Soviet soldiers inspecting a destroyed Panther with hull number 834. Kursk, 1943. Source: War Photo Archive via Yandex.Zen

By the middle of 1943, the Red Army already had experience in operating the PzKpfw.38 (t), PzKpfw.II, PzKpfw.III, and PzKpfw.IV, as well as self-propelled guns based on them. However, the use of Pz.Kpfw.V was a very difficult task, requiring appropriate training of crews and the availability of a repair base. Soviet tankers, lacking necessary experience in operating such complex and foreign equipment, often disabled Panthers after driving 15–20 km, and then could not repair them due to the lack of necessary spare parts, tools, and the experience in repairing such vehicles.

Line of Pz.Kpfw.V Panthers (T-V ‘Pantera’), from the 3rd Ukrainian Front, in Sofia, 1945, after being passed to the First Armored Brigade of Bulgaria. Source: War Photo Archive via Yandex.Zen

The headquarters of the 4th Guards Tank Army reported to the GBTU of the Red Army:

“These tanks (Pz.Kpfw.V) are difficult to operate and repair. There are no spare parts for them, which leaves no chance for their maintenance.
To fuel the tanks, it is necessary to provide for an uninterrupted supply of high-quality aviation gasoline. In addition, there are big problems with ammunition for the German 75 mm tank gun mod. 1942 (Kw.K. 42), since the ammunition from the gun mod. 1940 (Kw.K.40) is unsuitable for the Panther tank.
We believe that a German tank of the Pz.Kpfw. IV type is more suitable for carrying out offensive operations, as it has a simpler layout, is easy to operate and repair, and is also widely used in the German army.”

The captured Panthers from the 366th Gds. Heavy SP Arty Regt, 47th Army, vic. Lake Balaton. Hungary, March 1945. German numbers and emblemas are overpainted by red stars with white edges. Source:

However, since the Pz.Kpfw.V was armed with a gun with excellent ballistic characteristics, it had the ability to fight enemy armored vehicles at distances exceeding the effective firing range of Soviet 76 and 85 mm tank guns, which partially compensated for the complexity of its combat operation. In addition, the excellent, by the standards of that time, radio and aiming devices made the Panther a good command vehicle.
In the first half of 1944, the GBTU KA considered the use of serviceable captured Panthers as tank destroyers. In March 1944, a “Short Guide of Using the Captured T-V (‘Pantera’) Tank” was released.

Pz.Kpfw.V Panther (T-V ‘Pantera’) tanks, captured from the 5th SS Panzer Division “Viking”, as part of the 8th Guards Tank Corps of the Red Army, 1944. Source:

In January 1944, by order of the Deputy Commander of the 3rd Guards Tank Army, Major General Solovyov, one platoon of the most experienced repair engineers was created in the 41st and 148th Separate Repair and Restoration Battalions, which were later involved in the repair and maintenance of the captured Panthers. The 991st Self-Propelled Artillery Regiment (46th Army of the 3rd Ukrainian Front) had 16 SU-76Ms and 3 Panthers, which were used as command vehicles. In spring 1945, in addition to heavy ISU-152 self-propelled guns and several captured Hummels and Nashorns, there were 5 Pz.Kpfw.V and one Pz.Kpfw.IV in use in the unit.

Captured Pz.Kpfw.V Panther tank with Soviet identification signs — red stars, number 197. Source:

It is worth noting that the drivers of the Pz.Kpfw.V had to choose their route very carefully. In places where the light SU-76M passed freely, the heavy Panther could get stuck. Overcoming water barriers was also a major issue. Not all bridges could sustain a tank weighing 45 tonnes, and after fording a river, there were almost always difficulties in getting the Pz.Kpfw.V onto a steep bank.


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.VI Tiger II turret, the study of the change of armament on 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.
Another conversion that had to take place at that time was replacing the German 7.5 cm KwK 42 gun on the Pz.Kpfw.V Panther tank with the 85 mm Soviet one. Not many details are known about this project. The whole process of gun replacement was estimated at 120 hours of work. More than that, it is highly likely that the vehicle could also gain new Soviet sights and 7.62 mm machine guns instead of German Maschinengewehr 34 (MG 34).

Approximate number of machine-hours required to perform work on re-equipping captured German armored vehicles with Soviet guns in small-scale production. Source: CAMD RF 81-12038-775
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: ZiS-S-53

The exact model of the 85 mm gun is not mentioned in any of the known documents. Fortunately, it can easily be deduced. Firstly, a new gun was not an option, as in this case, rearming the Panthers would not fulfill the tasks set of a cheap and easily-made conversion. Secondly, the new gun should not have differed significantly from the 7.5 cm KwK 42 and allow the Panther to continue to perform as usual, without any impact on its mobility and other specifications. Hence, two main candidates appear: the 85 mm D-5T and the 85 mm ZiS-S-53.

The 85 mm D-5. Source: M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”
BR-365A BR-365K BR-365P OF-365K
9.2 kg 4.99 kg 9.54 kg
792 m/s 1050 m/s 793 m/s
0.164 kg TNT 0.048 kg charge
(0.07392 kg TNT eq.)
0.66 kg TNT
142 mm pen 145 mm pen 194 mm pen
6-7 rpm Parameters of penetration are given for 0 m and 0°.

85 mm D-5T parameters. (source — ZA DB, Pablo Escobar’s gun table)

The history of the 85 mm D-5T gun dates back to May 1943, when the Design Bureau of Plant No. 9 reworked the design of the U-12 gun and offered its own version of the 85 mm tank gun. The new product received the D-5T (or D-5T-85) index and differed from the U-12 by a semi-automatic breech mechanism borrowed from the ZIS-5 gun, as well as some recoil brake and recoil system assemblies. The tight layout of the gun and the short length of its rollback allowed it to be installed in the turret of any existing heavy tank without altering the turret. The gun compared favorably to the S-18 and S-31, with a small recoil length and breech mass, but had a large number of small details and parts, which required precise processing.
Four tanks were tested together (two IS and two KV-1S tanks), armed with S-31 and D-5T guns. Trials demonstrated the great operational advantages of the D-5T gun, which was adopted by the Soviet Army. At the same time, Plant No. 9 was preparing for the mass production of new guns. The peculiarities of the D-5T resulted in difficulties in production for the plant. The plan for the production of 85 mm tank guns for the KV-85 and IS-85 was hardly fulfilled by Plant No. 9, but its capacity was clearly not enough for another gun order for the T-34-85. Factories No. 8 and No. 13 involved in the production could not build this new gun, as they were unprepared for such a complex device. From 1st March 1944, the production of the 85 mm tank gun D-5T ceased.

The 85 mm ZiS-S-53 on trestles. Source: M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”
85 mm ZiS-S-53 APHE APCR HE
BR-365A BR-365K BR-365P OF-365K
9.2 kg 4.99 kg 9.54 kg
792 m/s 1050 m/s 793 m/s
0.164 kg TNT 0.048 kg charge
(0.07392 kg TNT eq.)
0.66 kg TNT
142 mm pen 145 mm pen 194 mm pen
7-8 rpm Parameters of penetration are given for 0 m and 0°.

85 mm ZiS-S-53 ammunition parameters. Note they were almost identical to D-5T’s. (source — ZA DB, Pablo Escobar’s gun table)

Fulfilling the order of the NKVD (rus. for ‘People’s Commissariat for Internal Affairs’) to create an 85 mm cannon for the T-34, TsAKB, alongside plant No. 92, quickly carried out complex design work and, by 10th December 1943, two 85 mm artillery systems, the S-50 and the S-53, were tested at the TSLKB firing range.
The S-50 gun (developed by V. Meshchaninov, L. Boglevsky, and V. Tyurin), which had improved ballistics (the initial velocity of the BB projectile was 920 m/s), was not so successful.
The S-53 differed from other similar guns in its simple design and reliability. It was created by the group consisting of I. Ivanov, G. Shabirov, and G. Sergeev. The recoil brake and the recoil system were moved under the base of the breechlock, which made it possible to reduce the height of the firing line and increase the distance between the breech section and the rear wall of the turret. The metal usage coefficient (the ratio of the mass of a part to the standard metal consumption for that part) in the S-53 was very high, and its cost was lower than those of the F-34 and the D-5T. Within 2 months, all the necessary design and technological documentation was prepared for the production of the gun, and on 5th February 1944, the gun went into mass production.

Comparison of the 7.5 cm KwK 42, 85 mm ZiS-S-53, and 85 mm D-5T’s virtual appearance. (Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich; based on original blueprints.)

Considering all the factors, the ZiS-S-53 seems to have been the most optimal choice for rearming captured German Panthers. It had a simple design, compact size, and was rather reliable. Moreover, in spring 1945, a version with stabilizer was developed, the ZiS-S-54, which could possibly have been installed later.

Project Description – Comparison with the Panther Ausf.G

The Soviet military command liked the proposal to instal the Soviet ZiS-S-53 gun, which had proven itself on T-34-85 medium tanks, in the turret of the German Panther tank. Its breech took the same amount of space as the German KwK 42, despite the larger caliber.

75 mm KwK 42 L/70 APHEBC APCR HE
PzGr 39/42 PzGr 40/42 SprGr 42
6.8 kg 4.75 kg 5.74 kg
935 m/s 1120 m/s 700 m/s
17 g charge
(28.9 TNT eq.)
725 g TNT
187 mm pen 226 mm pen
6-8 rpm Parameters of penetration are given for 0 m and 0°.

The 75 mm KwK 42’s ammunition parameters (source — ZA DB, Pablo Escobar’s gun table)

  • APHEBC – Armor-Piercing High Explosive with Ballistic Cap;
  • APCR – Armour-Piercing Composite Rigid
  • HE – High Explosive

All in all, the new Soviet gun was significantly worse than the German original in penetration and shell flight speed. On the other hand, the ZiS-S-53 was adopted by the Soviet Army in 1944, almost a year before T-V-85 was developed, hence its mass production was well organized by then, and soldiers were used to it.

Comparison of the T-V-85 and the Pz.Kpfw.V Panther’s turret inner layout.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

Like the T-VI-100 project, the T-V-85 would most likely have had similar changes. The German 7.92 mm MG 34 would have been replaced by the Soviet 7.62 mm DT and the TSh-17 sights (later used on the IS-2 and IS-3 Soviet tanks) would replace the original TFZ-12A sights. 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.

T-V-85 and Pz.Kpfw.V Panther elevation arc comparison.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

Unlike in the T-VI-100, the space inside the T-V-85’s turret would have remained almost the same as on the Panther. As a result, elevation arcs would have been nearly identical (-8°/+18° in the frontal part and -4°/+18° in the rear).
However, just like for the T-VI-100 proposal, many other problems would remain unresolved on the T-V-85. There were no considerations on replacing the transmission, engine, and other hull components with Soviet ones, which means that repairing the tanks would have been problematic. Obviously, had the T-V-85 been converted from Panthers, in field use, all the challenges associated in using captured German vehicles by the Red Army would have been preserved, to the great displeasure of 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.

T-V-85 inner layout scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The Panther itself was outdated by 1945 when compared to the newest medium tanks of that time, the Soviet T-44/T-54, the British Cromwell, Comet, and Centurion, or the American M26 Pershing. Its armor could no longer “surprise” anyone, but almost 50 tonnes of mass was a serious drawback. All this indicates that had the T-V-85 been conceived, it would have hardly been able to perform well, even as a tank destroyer.

The T-V-85’s armor scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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 for most of these, especially those that never operated such a medium tank before, the “Panther”, even with a 85 mm gun (even with stabilizer and newest post-war ammunition), would probably not have been needed. Germany itself was not allowed to have its own army for some years. For the emerging Soviet Bloc countries, such as Czechoslovakia, Hungary, or Poland, especially those bordering what would become NATO, the T-V-85 might have been a good temporary stopgap for their weakened armies until Soviet supplies of T-34-85s, 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. The first frontlines of a hypothetical Third World War would surely have been in Eastern Europe. On the other hand, it is doubtful that rearming an outdated, and difficult to maintain captured tank type was easier and more useful for the aforementioned countries than waiting for the mass-produced T-34 or T-54.


T-V-85 external appearance reconstruction.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

The T-V-85 tank project, like many of its counterparts, belongs to the category of “the war ended too soon”. 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.

T-V-85. Illustration by Godzilla
Pz.Kpfw. V Panther (T-V) tanks, captured from the 5th SS Panzer Division “Viking”, as part of the 8th Guards Tank Corps of the Red Army, 1944. Illustration by Godzilla
The captured Panthers from the 366th Gds. Heavy SP Arty Regt, 47th Army, vic. Lake Balaton. Illustration by Godzilla
Pz.Kpfw.V Panther (T-V ‘Pantera’) from the 3rd Ukrainian Front, in Sofia, 1945, after being passed to the First Armored Brigade of Bulgaria. Illustration by Godzilla
T-V-85 specifications table
Dimensions (L-W-H) Length: 8.86 m
Length (without gun): 6.866 m
Width: 3.42 m
Height: 2.917 m
Total weight, battle ready 45.5 tonnes
Crew 5 men (commander, gunner, loader, radio operator, and driver)
Propulsion Water-cooled, gasoline Maybach HL 230 P30 V12 motor producing 600 hp at 2500 rpm
coupled to a ZF A.K.7/200 transmission
Max speed 46 km/h (28.6 mph)
Range (road) On road: 200 km
Cross-country: 100 km
Primary Armament 85 mm ZiS-S-53
Elevation Arc -8°/+18° (frontal part), -4°/+18° (rear part)
Secondary Armament 2 x 7.62 mm DT
Hull Armor 85 mm (55°) upper frontal
65 mm (55°) lower frontal
50 mm (29°) upper side
40 (vertically flat) lower side
40 mm (30°) rear
40-15 mm (horizontally flat) roof
17 mm (horizontally flat) engine deck
30 mm (horizontally flat) frontward belly
17 mm (horizontally flat) rearward belly
17 mm (horizontally flat) pannier
Turret armor 110 mm (10°) frontal
45 mm (25°) side and rear
30 mm roof
№ built 0, blueprints only;

Special author’s thanks to his colleagues: Andrej Sinyukovich and Pablo Escobar.


Central Archive of the Ministry of Defense of the Russian Federation, 81-12038-775;
Russian State Archive of Film and Photo Documents;
M.A. Svirin, “Artillerijskoe vooruzhenie sovetskih tankov 1940-1945”;;;;;;;;;
Pablo Escobar’s gun parameters table;

WW2 Soviet Prototypes


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.

Tiger I external appearance.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Tiger I №211 near Belgorod, USSR. Source:

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

Red Army soldiers study a captured German heavy tank. January 18, 1943. Source:

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»

Soviet 57 mm guns easily penetrated the sides of “Tiger”. Source:

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.

“Tiger” after being shelled by a Soviet 122 mm A-19 gun. Source:

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.

KV-1 heavy tank after being shelled by the German 88 mm KwK 36 L/56 gun. Источник:

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.

Remains of T-34 after it was shelled by a German 88 mm KwK 36 L/56 gun. Источник:

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.

G.K. Zhukov, N.N. Voronov, and K.E. Voroshilov inspect the first captured “Tiger”. Source:

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”

T-VI-100 plan description. The writing in Russian says: “Installation of a 100 mm D-10T gun into the turret of a T-VI tank, longitudinal section”. Source CAMD RF 81-12038-775.

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.

Aforementioned blueprint of T-VI-100 turret (source — CAMD RF 81-12038-775) and its restored version. Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Approximate number of machine hours required to perform work on re-equipping captured German armored vehicles with Soviet guns in small-scale production. Source: CAMD RF 81-12038-775
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
  1. Head of Special Design Bureau (OKB-43) – Salin;
  2. 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.

D-10T gun (source —

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.

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.

T-VI-100 and Pz. Kpfw. VI Ausf. E elevation arc comparison
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 and Pz. Kpfw. VI Ausf. E turret inner layout comparison
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 armor scheme.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

T-VI-100 inner layout.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.


T-VI-100 external appearance reconstruction.
Source: Zinoviy Alexeev Design Bureau, drawn by Andrej Sinyukovich.

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.

Captured Tiger II №502, side view. Writing in the frontal part of the hull says “Glory to our people!” (rus. “Слава нашим”), and writing on the barrel of the gun says “Glory to Korobov!” (rus. “Слава Коробову!”). Source: Report of the Research Proving Ground on brief tests of the German Tiger-B tank.

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 in Soviet colors, with star emblem and writing “Tiger” – illustration by Pavel Alexe
Captured Tiger №121 with washed-off camo, used for durability tests in the USSR. Note the first road wheel is missing. – illustration by Pavel Alexe.
Captured Tiger №100 with washed-off camo, used for 8.8 cm KwK 36 tests in the USSR. – illustration by Pavel Alexe.
Tiger II №502, captured by Soviets. – illustration by Pavel Alexe.
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;


Central Archives of the Russian Ministry of Defense 81-12038-775;
Russian State Archive of Film and Photo Documents;;;;;;
Pablo Escobar’s guns’ parameters table;;

WW2 Soviet Prototypes


Soviet Union (1935)
Self-Propelled Gun – 1 Prototype Built

Prior to the Second World War, the Soviets were experimenting and developing a series of projects intended to improve the performance of already existing armored vehicles. One of these projects was an attempt to resolve the issues with the weak armament of Soviet amphibious tanks. This would lead to the creation of the experimental SU-45. While one prototype would be built, its poor performance would eventually lead to the cancelation of this project.

The SU-45. Source: Pinterest

The SU-37 project

The Soviet Scientific and Technical Department Agency of Automobiles and Tanks (which was part of the Ministry of Defense of Red Army) issued a request to the director of plant №37 to begin designing and building a new self-propelled vehicle based on the T-37A amphibious light tank. The timeline was quite short. The order was given on 22nd March and the first prototype was to be completed by 11th April the same year. In reality, this task could not be achieved effectively in such a short period of time.

The T-37A was an amphibious light tank developed during the early 1930s in the Soviet Union. It was lightly protected and armed with only a single machine gun. The crew consisted of the driver and the commander/machine gunner. The T-37A was primarily intended to perform reconnaissance operations. Over 2,000 vehicles would be built, with most being lost during Operation Barbarossa in 1941.

T-37A amphibious light tank. Source:

When the tactical and technical requirements arrived, they included an option to use either an unchanged T-37A chassis or to build a completely new chassis with some elements taken from this vehicle. Other requirements included a maximum weight of the vehicle of 3 tonnes. The armament would include one 45 mm gun with a traverse of 30° (in both directions) and elevation of -8° to +25° and a DP machine gun. The ammunition load for the gun was to be 50 rounds, with an additional 1,000 for the machine gun. The overall armor protection had to be at least 5 mm thick (except the roof, which would be open-top) including an armored shield for the gun.

The new vehicle, which would receive the SU-37 (Samokhodnaya ustanovka – self-propelled) designation, was to have the same amphibious properties as the T-37A. It should have supplemented the weak firepower of the T-37A formations with its stronger armament. In addition, it was to fulfill a mobile anti-tank role on a regimental level.

The improved SU-45 replacement project 

Despite the short-term development goal, the actual design work on the new self-propelled vehicle dragged on. Almost from the start, a number of problems arose. One issue was the weight of the new vehicle was much larger than expected. This prevented it from being able to cross water obstacles. Another even greater problem was that many components for the T-37A were no longer being produced. A team of engineers under the leadership of I. Arharov was tasked with resolving the problems with the SU-37 and trying to find a better solution.

In November 1935, a mock-up version of the new modified self-propelled vehicle was presented to the Agency of Automobiles and Tanks of the Ministry of Defense. The basis for this new vehicle was the T-38 amphibious light tank. The T-38 was an improved version of the T-37A. It had a slightly modified suspension, overall simpler construction, better buoyancy properties, and the turret position was changed to the left side of the hull. The armament, crew configuration, and armor were the same. Over 1,200 of his vehicles would be built from 1936 to 1939.

The T-38 amphibious light tank.

This vehicle incorporated the chassis, transmission, and engine from the T-38. The main gun was still the same 45 mm anti-tank gun. The driver/gunner was initially positioned on the right side. The commission requested that the driver’s position be changed to the left side and that he no longer have to operate the gun. The first prototype was to be built by the start of 1936.


In the documents of the Agency of Automobiles and Tanks of the Ministry of Defense, the project received the “SU-45” designation. It is somewhat confusing that the Soviet Military Authorities decided to name the previous prototype based on the chassis on which it was based (SU-37 from T-37A) and the second prototype by the main gun caliber. This designation practice would continue on, many later developed self-propelled vehicles receiving names based on their gun caliber.

Author D. Nešić, (Naoružanje Drugog Svetsko Rata-SSSR) notes that the designation for this vehicle was T-45. This should not be confused with a Soviet attempt to improve the T-60 tank during the Second World War. If this is a mistake or misunderstanding on behalf of the author is difficult to know.


Note that, due to the generally obscure history of this vehicle, sources greatly disagree about nearly all of the SU-45 components.


For the construction of the SU-45, a modified chassis of a T-38 light amphibious tank was used. The front part of the chassis housed the crew and the main gun. To the rear, the engine and the transmission were placed.

Engine and transmission 

The SU-45 was powered by a four-cylinder liquid cooling 40-45 hp GAZ-A engine. The maximum speed of the SU-45 with this engine, on a good road, was 45 km/h. The off-road speed and operational range are unknown. The GAZ-A engine was started by using a MAF-4001 electrical starter. The position of the transmission was changed to the rear.


With the increased number of crewmen, added ammunition, and other changes, the weight of the vehicle reached 4.5 tonnes (or 4.3 tonnes, depending on the source). The T-38 running gear had to be redesigned. This included adding an additional roadwheel (on both sides), making it five in total (from the original four on the T-38). While the added wheel was suspended individually, the remaining four were placed in pairs on a bogie suspension unit. All five wheels were rubber-tired. The idler and drive sprocket on the SU-45, in comparison to the T-38, had switched positions. The driver sprocket was now at the rear, while the idler was at the front. The two return rollers remained unchanged.

Side view of the T-38’s suspension, which had four wheels placed in pairs on two bogies. Note the Finnish swastika on the turret. Source:
Close-up view of the modified SU-45 suspension which included one additional road wheel and the changed positions of the idler and drive sprocket. Source: Pinterest


Not much is detailed in the sources about the superstructure’s design. The SU-45 was actually an open-topped vehicle. To shield the crew from the weather and elements, a canvas cover could be placed on top of the vehicle. Its overall construction, based on the few existing photographs, appears to have been simple in design. The SU-45’s side armor plates were flat, while the front plate was at an angle. The front, where the crew compartment was located, was slightly raised in comparison to the rear engine compartment. This was meant to provide the crew with protection but also to reduce the vehicle’s overall weight.

On the right front plate, a large square-shaped driver’s visor was placed. In its center, a smaller vision port was located. On the opposite side of it, a ball mount for the machine gun was located. Close to it, a pyramid-shaped cover can be seen. Its purpose is not clear, but it is likely to have been a protective cover for the gun’s sights.


The 45 mm M1932 anti-tank gun was chosen as the main armament of this vehicle. It was the standard Soviet infantry anti-tank gun prior to and during the first years of the war. While it would be replaced with larger caliber weapons, due to the large production numbers, it remained in use during the war. The 45 mm M1932’s armor penetration at 500 m (at 0 degrees) was 38 mm. The rate of fire was some 12 rounds per minute.

The 45 mm M1932 anti-tank gun. Source: Wiki

The main gun on the SU-45 was positioned in the front center of the vehicle. It was protected by a round shield placed in front of the gun. The elevation of the gun was -3° to +10°, while the traverse was 10° in both directions. The ammunition load consisted of (depending on the sources) between 50 to 100 rounds. The latter number seems to be unlikely, given the small size of the vehicle. The secondary armament consisted of one 7.62 mm DT machine gun. It was placed in a ball mount and positioned to the left side of the vehicle. It was operated by the vehicle’s commander. The ammunition load for this machine gun was around 1,100 rounds. The machine gun was also provided with a pivoting mount to be used as an anti-aircraft weapon.

Front view of the SU-45. The main weapon, with its curved gun shield, is located in the front. Left of it, the driver’s observation hatch with a small slit visor can be seen. On the opposite side, the machine gun ball mount (without the machine gun itself) is noticeable. Interestingly, sources like A.G. Solyankin (Отечественные бронированные машины. XX век Том 1) stated that this is not the SU-45 but the SU-37. Due to the general obscurity of the Soviet armored vehicles prototypes of the time, especially in western literature, this should not come as a surprise. Source: Pinterest

The Crew

Depending on the source, this vehicle is listed to have either two or three crew members. In case it had three crew members, these included a commander/gunner, loader, and the driver. Despite initial plans to change the position of the driver to the left, on the prototype, he was seated on the right side. The remaining crew members were positioned opposite the driver. The commander was overburdened, as he had to operate the gun and the machine gun and command the vehicle, greatly reducing his effectiveness.

Armor protection 

The SU-45 was lightly protected, with armor plate thicknesses ranging from 6 mm on the sides to 9 mm on the front. These armor plates were connected using screws and rivets. This armor thickness was sufficient, at best, against small-caliber bullets.

Ultimate fate

Despite the plans to complete the first prototype by January 1st, 1936, due to many delays, it was only completed in the spring of that year. Once ready, a series of trails with the SU-45 were carried out. During these, a number of flaws in the design were noted. The T-38 chassis was overloaded and often led to mechanical breakdowns. The engine was underpowered, with an ineffective cooling system which often led to overheating. The transmission was also problematic and unreliable.

Seeing the results of these trials, the Agency of Automobiles and Tanks of the Ministry of Defense insisted that all these flaws and problems be resolved. The experiment would be carried on to the experimental T-38M chassis, but ultimately lead nowhere, and the whole SU-45 project was scrapped.


The SU-45 was intended as a lightweight self-propelled vehicle which was to provide additional support fire for the amphibious light tanks in cooperation with other units. The SU-45 design ultimately proved to be a failure. Having too great weight prevented it from being used as an amphibious vehicle. The engine had overheating problems. While it had much-improved firepower in comparison to the vehicle it was based on, it retained weak armor protection. This vehicle would never enter production and the Soviet units had to rely on their obsolete T-37 and T-38 vehicles. During the Second World War, these also proved to be unsatisfactory designs in many regards.

SU-45 right side view
Left side
Front side
Rear side
Top view. All illustrations by Iustin Drăgan ‘Phantom_25_Sniper’ Nicolae, funded by our Patreon campaign.


SU-45 specifications

Dimensions (L-w-h) 4.2 x 2.36 x 1.62 m
Weight 4.3 to 4.5  tonnes
Crew 3 (Commander/Gunner, Loader, and Drive)
Propulsion 40-45 HP GAZ-A engine
Speed (road) 45 km/h
Primary Armament 45 mm M1932
Secondary Armament 7.62 mm DT machine gun
Armor 6 to 9 mm
Total production 1




Has Own Video WW2 German Heavy Prototypes WW2 Soviet Prototypes

Grote’s 1,000 tonne Festungs Panzer ‘Fortress Tank’

Soviet Union/German Reich (1932)
Superheavy Tank – None Built

In armored terms, few tanks evoke more awe in terms of size and specifications than the Maus, a 200-tonne behemoth from the tank-stable of the even more famous Dr. Porsche. It is also no secret that there is a certain following, especially online and in the media generally, for what could, at best, be described as ‘Nazi Wonder Weapons’. It is not that any one of these ideas could have won the war for Germany, that was simply not going to happen in 1945 regardless of whatever vehicle, missile, or plane the Germans developed. What they were, however, is a reflection of the giant level of engineering and imagineering which ran amock at times in Nazi Germany. A political mindset wanting a 1,000 year Reich was also thinking huge in every conceivable area, from giant planes to super-ships, rockets, and, of course, tanks. If the Maus impressed as a 200-tonne vehicle, then imagine a vehicle 5-times that weight; a true goliath.

Online, that vehicle has become known as the ‘Ratte’ (Eng: Rat), as some kind of allusion to its Maus-sized forebear, but the vehicle was less rat-sized and more landship-sized and was known under the less amusing name of ‘P.1000’. Perhaps even more surprising than its incredible weight and size was that this vehicle was not some late-war attempt to wrestle victory from defeat by overwhelming Allied superiority, but began life in the 1930s. More than that, it did not even begin life in Germany, but in the nation to become Nazi Germany’s greatest enemy, the Soviet Union.

The Men Behind the Tank

The primary figure in the story of the P.1000 is the enigmatic Edward F. Grote. (Note that his name is repeated numerous times online and in books as ‘Grotte’, but is very clearly written as Grote with one ‘t’ in both British and German patents, so his name assuredly was ‘Grote’). Grote’s work on huge tanks had begun early during the time he spent working in the Soviet Union (USSR). A skilled engineer, Grote had lived in Leipzig between 1920 and 1922, running an engineering concern where he had received several patents for engines, in particular diesel engine innovations. These included methods of cooling and also lubricating those engines with oil under pressure. Grote’s interest in power transfer and diesel engines would be very useful when it came to designing large and heavy tanks.

The Soviets

The Soviets had, after April 1929, tried to emulate the French FCM Char 2C with a project of their own. They had tried to engage foreign engineers and designers and were interested in the ideas of Edward Grote. Grote’s skills led him, by 1931, to become head of the Soviet design team for this new giant tank, his firm having been selected over two rival firms in 1930, primarily for political reasons – Grote was a sympathizer of the Soviet government and one of his engineers was a member of the German Communist Party. His task for the Soviets was to develop a breakthrough tank able to match the French FCM Char 2C and the order for this work was dated 5th April 1930. At the time, the specifications for this breakthrough vehicle were perhaps somewhat unremarkable, with a weight of just 40 tonnes and armor not less than 20 mm thick.

A design bureau known as AWO-5 was set up in Leningrad (now St. Petersburg) for him to conduct this work. By 22nd April 1930, just over two weeks since the task was officially set, the preliminary outline was ready. This design became the first in a series of ‘TG’ tanks – TG for ‘Tank Grote’.

Photo of the staff of the Leningrad design bureau AWO-5, taken in 1931. Edward Grote sits in the centre on the front row. Source: Frohlich

The Soviet TG or TG-1 tank was designed with the involvement of Edward Grote.

In just over a year, the first prototype was ready for trials, but the novel track design was a particularly weak point of the design. Added to this was that the cost was excessive, to the extent that the BT-5, an 11.5-tonne tank with an armor of just 23 mm at best, was preferred instead – hardly suitable for a breakthrough role, although its speed would be useful for exploitation of a breakthrough.

Soviet BT-5 tank (with tracks removed) at Kubinka, Russia.
Source: Craig Moore

More versions of the TG followed and it inevitably grew larger, heavier and more complex in doing so, with the sixth and final version presented in May 1932. By this time, the Soviets had seemingly grown weary of a project which was producing increasingly large and expensive tanks when there were alternatives available, such as emulating the British A1E1 Independent.
The result was that the Soviets turned from this German design to their own vehicle inspired by the British A1E1 and which was ready in 1933, in the form of the T-35A. At over 45 tonnes, this tank was large – nearly 10 m long, and was fitted with 5 turrets, although armor was just 30 mm at best.

Soviet T-35A
Source: Wiki

The First Fortress Tank

Grote, however, had not given up on his increasingly large tank ideas. It is worth noting that the big size limiter for tanks is based around the size and weight which can be borne by roads, and especially railways. These limitations restrict the maximum width and height of the vehicle more than the length. This has historically resulted in some very long vehicles, as the designers of the vehicles struggle to provide the armor and automotive power within these strict limits.

Grote, and several designers before and since, have understood that, as soon as you step beyond these maximums, there is no point in a vehicle a little wider or a bit taller than could be carried by train. Indeed, the decision to go big from a design point of view is technically very freeing, as the dimensions can be made whatever they need to be to fulfill the role of the vehicle. If, like it was for Grote, the need was for a well-protected breakthrough tank with a lot of firepower, then freeing himself from those strict limits meant he could make a big tank to mount big guns. It would need a big engine or engines to power it but, again, there was effectively no limit on the volume into which the unit or units required to power the vehicle could fit.

Liberated from the width and height restrictions of the rail gauge, Grote had gone beyond the plausibility of his TG vehicles and, in March 1933, submitted a new, massive, and less plausible vehicle concept to Soviet Marshal Mikhail Tukhachevsky. Tukhachevsky was a key figure in Soviet military modernization in the 1930s before he, like millions of others, fell victim to the murderous purges of Joseph Stalin. The dimensions of the vehicle were truly staggering. A hull 34 meters long, 10 meters wide, and 11 meters high, it was topped with a pair of 305 mm guns in fully rotating turrets. A pair of smaller turrets, each fitted with a pair of 152 mm guns, were mounted on the front corners of the hull, and two more turrets, each fitted with a pair of 76 mm guns, were fitted aft of the primary turrets. If that was not enough firepower, two further turrets, each fitted with a 45 mm gun, were also to be mounted.

The sides of the hull were vertical and used heavy armor plating 250 mm thick to cover the enormous road wheels* and suspension. The front of the tank was very well angled and was to be 300 mm thick. This 300 mm of armor was to be repeated on the front of the primary turrets and roof armor was to be 100 mm thick. Certainly, this would have been sorely needed given the size of the tank and what a target it would have made for enemy artillery or aircraft. The thinnest part of the armor was the hull floor, at 60 mm thick.

Supported on a trio of 1 m wide tracks on each side, there would be 6 m of track width on the ground. Given that the vehicle was estimated to weigh 1,000 tonnes, this track, with a ground contact length of 20 m, spread the great load and the ground pressure was calculated to be just 0.72 kg/cm2 (about half that of the 180 tonnes Pz.Kpfw. Maus), a little more than that exerted by a heavily laden man’s foot. This was truly the Festungs panzer or ‘Fortress’ type tank Grote was picturing, with a crew of not less than 40 men to command, drive, maintain and operate all of the weapons, but it was also no slouch despite its huge mass.

(* assuming the 1942 rebirth was just a revamped version of his 1933 idea, then the wheels would be around 2.5 m in diameter)

By virtue of twelve 2,000 hp 16-cylinder diesel engines (24,000 hp / 17,630 kW total) and a special hydraulic transmission, Grote expected his 1,000 tonne monster to manage up to 60 km/h. One of the crucial advantages the enormous size would give Grote would be the obstacle-crossing ability of the tank. With its high leading edge of track, his tank would be able to climb a vertical step no less than 4.8 m high and ford an 8 m deep river without having to concern itself with bridges.

With the design submitted, it was reviewed and found to have serious problems. Not the least of these was that the planned engine power and speed of the vehicle were not realistic. There was simply no engine producing 2,000 hp available. The V-16 (cylinders at a 50-degree angle) 88.51 liter Mercedes-Benz MB502 marine diesel engines, could, at best, produce just 1,320 hp at 1,650 rpm or a continuous output of 900 hp at 1,500 rpm. Assuming 12 of those could be used, then this would produce a continuous 10,800 hp or a maximum of 15,840 hp, well short of the 24,000 hp needed. The engines were to have been laid out 6 on each side and all driving a common driveshaft. This power was then to be transmitted either hydraulically or electrically to the drive sprocket.

Mercedes-Benz MB-502 V-16 diesel engine.
Source: Pearce

A supercharged version of that engine was also available later, but this was not in production when Grote’s design was submitted. That engine, the MB-512, could produce the same continuous 900 hp as the MB-502 at 1,500 rpm, but an improved 1,600 hp maximum output at 1,650 rpm. Even if this improved version was available to Grote, it would, at best, have delivered just 19,200 hp combined maximum – just 80% of what he needed.

With no suitable engine available, the Soviets could not accept Grote’s design and would soon part company with Grote and embark on their own fortress-tank work. With the failure of the TG tanks and now this fortress tank, Grote’s work in the Soviet Union came to an end and he returned to Germany in 1933.

Back to Germany

Grote, now living in Berlin, did not stop his engineering and submitted another patent application in 1935. Several more patents followed, relating to transmissions and hydraulic couplings but also, and more importantly, for tracks as well.

Grote’s transmission design of 1936.
Source: British Patent GB457908.

In January 1935, Grote filed a patent application for a novel type of caterpillar track. In his design, half of the metal links of a common style of track were to be replaced by intermediate links made of rubber sandwiched between the steel links. These rubber links would be in compression all the time, squashed between moving metal links on each side. The design would serve not only to create a lighter type of track but also one completely under tension the whole time, which would improve the efficiency of the driving force applied to the track. Perhaps more unusually, none of the links were actually physically connected together in the sense of a track pin. Instead, each track consisted of a pair of flexible chains, rather like the chain on a bicycle or chain saw, which would loop around the drive and road wheels. Each metal link would have two hollow channels made in it for each of these chains to pass through, and then, between each metal link, two of these smaller rubber intermediate links were placed, each with a single channel for the drive chain to pass through. The rectangular shape of the chain and of the channel in both the rubber intermediate links, and the metal links also prevented twisting of the links, or, in the case of the rubber links, any rotation from taking place. As the entire system was in compression the whole time, it also served to provide a completely sealed track system for the chain, so as to keep out dust, which would otherwise increase the wear and tear and reduce the track’s service life. Unlike a continuous rubber belt type track system, where damage means having to replace the whole length of track, this idea meant that localized repair was possible.

Grote’s unusual rubber intermediary link track design of 1935.
Source: German Patent DE651648

Another of his patents, submitted in 1936, was for a moveable caterpillar track system. In that invention, the leading edge of the track could be changed so as to be low during road movement or raised to climb obstacles. There is no mention of tank design in either the metal-rubber-metal track design patent or in the elevated track patent, so it might be assumed that there was no military element involved in his designs.

Grote’s tracked vehicle patent of June 1936, showing how the leading wheel of the track could be raised to improve obstacle crossing.
Source: German Patent DE632293.

Arguments with Burstyn

With some tank-related patents behind him, Grote saw himself referenced indirectly in a December 1936 magazine article that had stated that a German engineer had designed a 1,000-tonne tank for the Soviets. Grote chose to write his own piece in response defending the size of the vehicle he had designed and this appeared in the Kraftfahrkampftruppe magazine in 1937.

In doing so, Grote had managed to earn the ire of Günther Burstyn, the same Günther Burstyn who designed a tracked vehicle in 1912 and had tried, unsuccessfully, to get interest from the Austro-Hungarian Empire in the idea. Burstyn was scathing in his own views on Grote’s concept, saying it was not only impractical due to its size, but also had no military utility, perhaps forgetting how naïve and impractical his own idea had been.

Sporting no less than seven turrets, Grote’s 1,000 tonne Panzer, as it appeared in Kraftfahrkampftruppe magazine in September 1937. Note that Grote’s name in the bottom right corner is clearly ‘Grote’ and not ‘Grotte’. Note also that there are 6 sets road wheels shown.
Source: Frohlich.
The same type of artist’s view as that in Kraftfahrkampftruppe magazine but with a different arrangement of turrets, wheels, mud chutes, and gawking onlookers. Note that there are 9 sets of road wheels shown.
The size of the figures next to Grote’s idea really illustrates the gigantic proportions he was thinking in.
Source: Frohlich
Another view of Grote’s vision of a giant multi-turreted, 6-tracked behemoth. Note that the central tracks of each trio is clearly recessed from the outer and inner track on each side. It is unclear if that was a deliberate part of the design or if it is a misunderstanding by the artist. Source: Frohlich

Burstyn’s primary complaint was the weight of the vehicle based on the false assumption that more mass meant it would be immobile. The ground pressure for such a massive machine was not particularly great, as it was to have 6 sets of tracks, with each putting around 20 meters of track on the ground. With each track 1 meter wide, 6 of them, with 20 meters of length meant a track contact area of 120 m2 (20 m x 6.0 m) and producing a ground pressure of 0.72 kg/cm2, very low for a vehicle of its dimensions. For reference, the German Pz.Kpfw. VI Tiger produced around 1.04 kg/cm2

Further to this, Burstyn was also critical of the top speed. The desired top speed of 60 km/h was not possible with the engines available at the time but Burstyn did not claim it was impractical for that reason, instead, it appears to be based on the notion that big equals slow. Certainly, 60 km/h was not going to be possible even under the best of situations, as the engines required were lacking, but even assuming he could manage half of the required engine power, it is fair to assume Grote’s design would at least have matched the comparatively slug-like 15 km/h top speed of the French FCM Char 2C. Further, the role such a gigantic vehicle would have to perform in smashing enemy lines, positions, and formations, and high speeds would not be needed anyway. It could not go so fast as to outstrip accompanying and supporting vehicles and troops anyway.

Unlike the FCM Char 2C, Grote’s Fortress tank concept would not use multiple small road wheels but would, instead, use several (the exact number varies in the artist’s impressions) very large diameter (~2 – 3 m) double road wheels per track section. Each of these sets of wheels was mounted into a bogie and that bogie was sprung by means of hydraulic cylinders with a compensator of some type. Steering would be produced by simply braking one side of the tank.

On the matter of immobility, Burstyn was simply incorrect and working on an incorrect premise. He was not, however, wrong in his critique of the military utility of the vehicle, but Grote would have a long way to go before he could prove or promote his ideas again.


The 1933 concept was the culmination of tank work in the Soviet Union, where the tank had got bigger and bigger to accommodate more and more armor and firepower and the larger and larger engines needed to propel the machine. Trying to achieve the goals of heavy armor impervious to enemy fire, heavy armament, and high mobility seem impossible at first glance, especially given the inherent constraints on the size of a vehicle. As Grote would find, the only way to achieve everything he wanted was to step out of the physical limits imposed by things outside of tank design, such as road widths, bridging, and rail gauges. Once those limits were exceeded even slightly, there was suddenly no real limit on the size of the machine and he could start with huge amounts of firepower and massive sections of armor. In doing so, he also would need a means of propulsion which was not available to him at the time. The ‘1,000 tonnes’ was probably as a symbolic weight that might grab the attention or funding which an ‘872 tonne’ design might not, but Grote had embarked on a slippery slope with no limits imposed. The end result was a gargantuan machine which, whether or not it would even move, was irrelevant to what practical use it could possibly have had.

Untethered from the reality, limits on size the machine had grown perhaps way beyond what he had wanted, to a vehicle of huge proportions with a ludicrous array of armament. Grote’s design, quite rightly, was rejected by the Soviets, for whom a simpler and more conventional machine, well armored and armed, would find favor well after the T-35A.

It is perhaps ironic that the lessons learned by the Soviets from this German flight of fancy had to be relearned by the Germans a few years later. Grote, in fact, went on to further refine his ideas. During that development, the dimensions were still gargantuan for a tracked armored fighting vehicle, but the design did at least get a little less ridiculous as it went on, at least in terms of fewer turrets. The weight and armament of those designs, however, remained excessively large and they were equally unsuccessful.

The shorter version of the 1000 tonne Festungs Panzer, showing the completely unworkable layout of the vehicle. Illustration by Andrei ‘Octo10’ Kirushkin, funded by our Patreon campaign.


Pearce, W. (2017). Mercedes-Benz 500 Series Diesel Marine Engines.
Pearce, W. (2017). MAN Double-Acting Diesel Marine Engines.
Frohlich, M. (2016). Uberschwere Panzerprojekte. Motorbuch Verlag, Germany.
CIOS report XXVI-13. Reich Ministry or Armaments and War Production. Section 16: Interview with Speer and Saur.
German Patent DE385516, Im Zweitakt arbeitende Verbrennungskraftmaschine, filed 25th April 1920, granted 24th November 1923.
German Patent DE370179, Verbrennungskraftmaschine, filed 25th April 1920, granted 27th February 1923.
German Patent DE344184, Zweitaktverpuffungsmotor mit Kolbenaufsatz, filed 4th June 1920, granted 21st November 1921.
German Patent DE370180, Verfahren fuer Gleichdruckmotoren, filed 26th October 1920, granted 27th February 1923.
German Patent DE370178, Verbrennungskraftmaschine, filed 7th January 1921, granted 27th February 1923.
German Patent DE373330, Schwinglagerung fuer Kolbenbolzen, filed 5th May 1922, granted 10th April 1923.
German Patent DE391884, Vorrichtung zur zentralen Schmierung von Maschinenteilen an Kraftmaschinen, filed 18th June 1922, granted 12th March 1924.
German Patent DE741751, Stopfbuechsenlose Druckmittelueberleitung von einem feststehenden in einen umlaufenden Teil, filed 6th January 1935, granted 17th November 1943.
German Patent DE636428, Stuetzrollenanordnung an Gleiskettenfahrzeugen, filed 6th January 1935, granted 8th October 1936.
German Patent DE686130, Geschwindigkeitswechselgetriebe, filed 6th January 1935, granted 3rd January 1940.
German Patent DE710437, Stopfbuechsenlose Druckmittelueberleitung von einem feststehenden in einen umlaufenden Teil, field 6th January 1935, granted 13th September 1941.
German Patent DE651648, Gleiskette mit Zugketten und einzelnen Metallgliedern, filed 6th January 1935, granted 16th October 1937.
British Patent GB457908, Improvements in and relating to Change-Speed Gears, filed 5th February 1936, granted 8th December 1936
US Patent US2169639, Clutch mechanism for change-speed gears, filed 20th May 1936, granted 5th January 1935
German Patent DE632293, Gleiskettenfahrzeug, field 11th June 1936, granted 6th July 1936.
French Patent FR817411, Dispositif de transmission d’un fluide sous pression, filed 5th February 1937, granted 2nd September 1937
German Patent DE698945, Kugelgelenkige Verbindung zweier mit gleicher Winkelgeschwindigkeit umlaufender Wellen mittels in Gehaeusen der Wellen laengs verschiebbarer Gelenkbolzen, filed 31st March 1937, granted 20th November 1940.
German Patent DE159183, Druckmittelüberleitung von einem feststehenden in einen umlaufenden Teil, field 14th March 1938, granted 25th June 1940.
German Patent DE159429, Druckmittelüberleitung zwischen zwei gegeneinander umlaufenden Systemen, filed 14th May 1938, granted 26th August 1940.
Belgian Patent BE502775, Einrichtung zur Befestigung eines Bolzens in einem Werkstueck, filed 25th April 1950, granted 15th May 1951.
German Patent DE842728, Einrichtung zur Befestigung eines Bolzens in einem Werkstueck, filed 28th April 1950, granted 30th June 1952. 28cm/52 (11”) SK C/28 28cm/54.5 (11”) SK C/34
MKB Ørlandet

Grote’s 1,000 tonne ‘Festungs Panzer’ concept, March 1933 specifications

Dimensions 34 m Long x 10 m Wide x 11 m High
Total weight, battle ready 1,000 tonnes
Crew 40
Propulsion 12 x 2,000 hp
Speed (road) 60 km/h desired
Armament 7 turrets;
1 x twin 305 mm, 2 x twin 152 mm, 2 x twin 76 mm, 2 x 45 mm
Armor 300 mm front, 250 mm sides, 100 mm roof, 60 mm floor
For information about abbreviations check the Lexical Index
Has Own Video WW2 Soviet Prototypes

GAZ-68 / KSP-76

Soviet Union (1943-1944)
Wheeled Infantry Support Gun – 1 Built

The SU-76 remains, to this day, one of the most well-known Soviet self-propelled guns of the Second World War. Yet, at the start of its production, it was plagued by unreliability and mechanical issues caused by its drivetrain. Thus, production was halted at only 560 units in order to remedy these problems. Solutions came with the SU-76M in 1943, but in between this period, another vehicle was designed, not to replace the SU-76, but rather supplement it. This was the GAZ-68 (also later referred to as KSP-76). Meant as a desperate and ultimately unsuccessful attempt to bolster tactical mobility, it was meant to provide close support artillery for rifle and cavalry units through direct fire. The GAZ-68 was based on a truck chassis, and the main gun would still be the famous ZiS-3 field gun.

SU-76M in what seems like Berlin, 1945. The SU-76M was an attempt to fix some problems with the SU-76. The GAZ-68 was a different vehicle in its role but would have functioned alongside the SU-76s.
Source: Pinterest


Throughout the early stages of the Second World War, the Soviet military found itself in a dire need of a fast vehicle, with good firepower, able to take on German Panzers but also other targets. Mainly, it would assist the infantry units in dealing with armored and unarmored targets, but also have the capability of responding quickly, moving and penetrating deep into enemy lines, accompanied by infantry attacks. Until 1943 and ‘44, the RKKA had no designated infantry support vehicle, relying entirely on towed artillery. Using a wheeled chassis as a basis, would allow much greater on-road speed, while also, theoretically, keeping production and maintenance costs down. On paper, a vehicle like the GAZ-68 was just what the Red Army needed, but in reality, it was the complete opposite, a consequence of the Soviet war and industrial struggle. Contrary to popular conceptions, this vehicle was not meant for artillery units for indirect fire or ‘shoot and scoot’ purposes, rather just an infantry support gun.

Front of the GAZ-68 as it is preserved at Kubinka, Moscow.
Source: A. Tarasov’s personal collection


Shortly after the battle of Kursk (July – August 1943), where the use of mobile defenses and counter-attacks (plus numerical superiority) proved key for the Soviet victory, the mobility of artillery and self-propelled guns proved crucial. Thus, the Gorky Automobile Plant (Gorkovsky Avtomobilny Zavod, GAZ) started the development of a wheeled infantry support gun with the approval of the head of GAZ, V.A. Grachev, who was head designer of the project, while N. Astrov was head of the project. Already in August of 1943, the design office and plant management approved the idea. Grachev, a lesser-known name within western literature, was the chief designer at GAZ between 1941 and 1944 when he created many vehicles, most notably the GAZ-64 and BA-64. Post-war, he continued his career at ZiL, where he created, among others, the famous ZiL-157 and BTR-152.

The first ideas involved mounting a ZiS-3 gun on a 1½ tonne truck chassis, with only minor modifications. Clearly, the main goal here was to get a mobile vehicle for as little money as humanly possible.

Drawings for the installation of a ZiS-3 76 mm gun on a truck chassis, which has been stripped down to the bare minimum, missing even an enclosed driving cabin. For obvious reasons, the combat value of such a creation would be extremely limited.
Source: Солянкин А.Г., Павлов М.В., Павлов И.В., Желтов И.Т. Отечественные бронированные машины. XX век. Том 2. 1941-1945

The idea of a wheeled infantry support gun interested the Soviet military, leading to a go-ahead to the project from the People’s Commissariat (Ministry) of Medium Machine Building and the Main Armored Directorate of the Red Army (GABTU). Previously, all self-propelled artillery projects were under the command of GAU (Main Artillery Directorate), until all the SPGs were re-subordinated to GABTU as Stalin personally was outraged that the GAU adopted SU-12 (SU-76) in an unsatisfactory condition. Thus, the Directorate of the Self-Propelled Artillery of the GABTU was established on the 21st of May 1943.

Work started in October of 1943 under the name ‘Izdelie 68-SU’, but this was changed to GAZ-68. By December, a wooden mockup was already completed and documentation on the vehicle from GAZ was sent to the GABTU in mid-December. The GABTU approved the project for further development. On the 7th of February, 1944, the GABTU gave a green light for the production of a prototype. It was around this time that the name ‘KSP-76’ appeared, most likely a product from GABTU to remove the GAZ factory name. It stands for Wheeled Self-Propelled Gun with a 76 mm gun (‘Kolyosnaya Samokhodnaya Pushka’, KSP).

An experimental model of the wheeled self-propelled gun KPS-76.
Curiously that the name in the document is КПС-76 (KPS-76), not KSP-76.
Source: TsAMO

Following the approval for a prototype, the design bureau quickly sent the plans and documents to the workshops, which meant that, by April, the armored hull was completed. This was designed by Y. N. Sorochkin and A. N. Kirilov and was to protect from small arms fire and splinters. To keep weight down, the top was left open. On the 4th of May, the prototype was already completed.

An important part of this quick development and production process was the use of an already tried and tested chassis (not that this meant much for the Soviets, as there were plenty of prototypes in all fields made pre-war, but in this case, it did help boost development). The GAZ-68 was based on the GAZ-63 truck, however, it needs to be pointed out that the production of the GAZ-63 began only in 1948. Rather, the GAZ-68 was based on the experimental GAZ-63 developed in 1939. Essentially this was an all-wheel-drive GAZ-51, which itself was made to replace the aging GAZ-MM. Ironically, a GAZ-MM superstructure was used for the prototype. A Dodge D5 Diesel engine was used, outputting 76 horsepower, coupled to a 4-speed transmission. These trucks were tested at Kubinka in 1940, with good results. Mass production was to begin in 1942, but the start of the Great Patriotic War (as WW2 is called in Russia) meant that all projects were canceled.

The GAZ-63 model 1939. Not to be confused with the GAZ-63 model 1948.

Grachev, very sensibly so, claimed that using this already finished and tested chassis would greatly increase the development speed and trials. The advantages of a wheeled vehicle over a tracked one are also clear, with cheaper maintenance and higher speeds on roads. The designers wanted to use as many readily available components as possible for reliability and production purposes. This idea was, however, the one that led to the GAZ-68’s demise.


The GAZ-68 was surely an unorthodox vehicle, especially by Soviet standards. However, at its core, it was essentially a SU-76 on wheels, albeit 69 cm narrower, 65 cm lower, and 135 cm longer.

The superstructure was thinly armored, made from a simple box, and no roof. The gun was mounted slightly behind the front wheel axle. The driver was located to the right of the gun, and with the gunner to the left. Ammunition was stowed to the sides of the casemate and behind. Thanks to the long wheelbase, the vehicle was very low to the ground, ideal for ambushes and camouflage, but also offered good stability. The engine was located at the back, over the rear axles. The design was rudimentary and simple, allowing for a very cheap vehicle to manufacture if the situation of Soviet truck plants was not as disastrous as it was. The top could be covered with a tarpaulin to protect from precipitation and wind. Two large fenders would protect the front wheels. As a result of the lack of resources, automotive plants were forced to take shortcuts during production, such as fitting just a single headlamp. On the GAZ-68 it was placed on the left side fender, to not further impair the view of the driver. Coupled with the low-mounted gun, these give the GAZ-68 its iconic look.

The very low profile of the GAZ-68/KSP-76 can be seen here. It was only 155 cm tall, 54 cm shorter than the SU-76. This would have made it a smaller target, crucial for a vehicle with such little armor.


The vehicle had a crew of only 3, a gunner (who also served as a commander and radio operator), a driver, and a loader. The gunner was responsible for aiming and firing the main gun. He had two vision slits through which he could see, plus the scope of the ZiS-3 gun, extending above the frontal shield. If in doubt, he could just stick his head up to get a clear 360° view using a pair of binoculars. The gunner also had a panoramic sight at his disposal.

Overloading the gunner/commander with so many tasks is unusual for the Soviets, especially in a late 1943 design and it is noteworthy that there was also enough space in the vehicle to put a fourth crew member, although test reports claim other crew positions were cramped. It is also worth mentioning that the Soviets had already suffered catastrophic losses, especially in specialized troops, such as tankmen. This might have been a deciding factor.

Commander/Gunner’s location. Radio and equipment have been removed, but the sight is still there.

As mentioned previously, the driver sat on the right. He had a slightly larger viewport to view out of compared to that of the commander. Oddly, the large steering wheel went above the viewport, which could have been inconvenient for taller drivers.

Driver’s position. Most of the electronics and dials have been removed, but there probably were not many to begin with. Note the large viewport.

The loader was seated behind the gunner, on a foldable seat. He had a ready rack behind him, incorporated into the engine compartment and in front of the fuel tank, which was not very safe, but considering the overall protection, or lack thereof, it did not matter. Forty-one rounds were stored here, in a horizontal position. 13 more rounds were stored on the other side, vertically, behind the driver. The crew also had 2 PPSh submachine guns for self-defense, with 12 magazines (852 rounds).

View from the front of the rear of the fighting compartment. Note the foldable loader’s chair on the right. The rack is right behind him, but is, in this picture, almost obscured by the cover. On the left, the other rack can be seen, and other storage spots.


The armament of the GAZ-68 was the trusty 76 mm M1942 ZiS-3 divisional gun, one of the most common guns within the Red Army at the time, and also the main weapon of the SU-76. The field gun was capable of both direct and indirect fire (once mounted on the GAZ-68 it was not). Over 100,000 units were produced by the end of the war and saw service post-war with many nations. It had a range of above 10 km and could use a variety of shells.

The KSP-76 would have most likely used AP and HE shells, but there were AP, APHE, HE, HEAT, Fragmentation, and other shells available. Most shells weighed around 6 kg and had a muzzle velocity between 680 and 700 m/s. On the KSP-76, 54 rounds were stored in total. The position of the gun in such a low profile vehicle affected its ergonomics compared to a regular field gun mount. The gun could only be elevated to +15° and depressed to -3° and had a horizontal traverse of 37°, 18.5° to both left and right sides of the gun.

The gun was supported by a travel lock mounted on the edge of the frontal slope. Despite the rather large compartment, the estimated rate of fire was 8 rounds per minute (one round in 7.5 seconds). The ergonomically well-placed ammo rack could have allowed an experienced loader to shorten the reload time even more.

The vehicle lacked any secondary armament, which was a common defect in Soviet SPGs, making them extremely vulnerable in close range combat with infantry, exactly the type of engagements the KSP-76 was meant to tackle.

View of the vertical breech and aiming system to the left.
The iconic recoil system of the ZiS-3 mounted on the KSP-76.


The armor of the vehicle was thin, only being able to withstand rifle fire and shrapnel. The GAZ-68 was never meant to be well armored in order to keep costs and weight down, plus its low silhouette would have played a big role in improving its survivability. The frontal plate was initially 10 mm thick, later increased to 16 mm. The top of the sides was 7 mm and the inwards angled bottom side plates 4 mm. This was not even bulletproof but would provide some protection against shell splinters and ricochets. The roof of the engine compartment was 5 mm thick but there was no protection over the heads of the crew apart from their own helmets leaving them, and some of the ammunition dangerously exposed. The cutting of corners and economy made in this aspect of the vehicle made it have a low unit production cost but would have clearly made it vulnerable to even rifle rounds from the side. The tires were bulletproof, filled with an elastic substance.

External view of the front corner, driver’s side. Note the thinness of the welded front and side plates. There were small covers for the viewports, but these seem to have vanished.

Engine and Chassis

The chassis was, as previously stated, that of the GAZ-63 model 1939 truck. The engine and transmission were changed from the truck to a single GAZ-202 (some sources state that the engine was a GAZ-202, but the TsAMO document states that it was a GAZ-203), engine outputting 85 hp, mounted in the rear compartment, offset by 276 mm to the right. To the left of the gun, a 140 liter insulated fuel tank was placed. In front of this, the 41 round ammo rack was placed. A very scary thought, considering the armor was only a few millimeters thick! An upwards-facing cooling grille was placed in the back. The transmission was a 5-speed manual (4 forwards, 1 reverse) coupled to both axles. However, the rear axles could be disconnected from the drive when not needed such as on a long road march. The suspension was standard and common to the truck consisted of simple leaf springs and shock absorbers.

Rear top view of the prototype. The rear compartment housed the engine, transmission, fuel tank, and ammunition, with only 4-7 millimeters of protection.

Trials and Fate

As soon as the prototype was finished, it began factory testing around May 1944 and had finished tests by autumn of the same year. From the Gorky factory, the GAZ-68 went to the Kubinka test range. Allegedly, it traveled under its own power and with an impressive speed of 60 km/h. Again, this information has to be taken with a grain of salt.

In September-December 1944 the experimental SPG was tested at Kubinka proving grounds and Gorokhovetskii artillery range. During a 2,528 km test drive, it is claimed to have reached a top speed of 77 km/h on-road, but this seems hardly possible in regular conditions. Even if it was true, the limited view of the driver would make such a speed hazardous, to say the least. The vehicle only had an 85 horsepower engine and weighed 5,430 kg battle-ready. During firing trials, 409 shots were fired of unspecified type at the Gorokhovetskii artillery range.

However, testing was not all going to plan for the Soviets. The original chassis took a hard beating and broke down frequently, putting into question the validity of the tests made at Kubinka of the GAZ-63. The driveshafts, gearbox, leaf springs, and frontal axle suffered some form of damage. To be fair, the GAZ-68 did weigh over 2 tonnes more, with different weight distribution. It was also noted that the crew compartment was too small and uncomfortable for some of the crew, especially the driver, who was cramped up by the gun and steering wheel.

The small silhouette and profile of the vehicle were deemed as a plus. However, there were significant issues with accuracy, thanks to the chassis and the suspension, which made the ride very bouncy. This also caused the sight and barrel to become misaligned after driving. Off-road tests were a mixed bag. On one hand, the GAZ-68 proved satisfactory, on the other, it was far inferior to what a tracked vehicle was capable of. Testing was finished by the 24th of December. The Military Council of the Armored and Mechanized forces of the Red Army (Военный Совет БТ и МВ КА, Voennii Sovet Bronetankovyh i Mekhanizirovannyh Voisk Krasnoi Armii), proposed to GOKO (State Committee on Defence) to produce the initial test batch of 10 units at the GAZ factory and undergo army tests. However, this was not achieved and, instead, the project was terminated altogether.

The situation of the war in mid-1944 was very different than that of a year earlier. The Red Army had been on the offensive for almost a year, pushing the Axis almost back to the pre-war borders, and the Allies had just landed in Normandy, sealing the fate of the war. The implementation of the GAZ-68 made even less sense now than it did before, and the questionable combat value it would have brought would far outweigh the industrial strain, despite the seemingly cheap production price.

Doomed from the start

Even before starting prototype production, the fate of the GAZ-68 was predetermined. The straightforward fact that it was based on a truck chassis, which for the designers certainly seemed like an advantage, but the industrial capabilities and resources of the USSR could not deliver. The Soviet industry could not keep up production of ZiS-5 and GAZ-AA simple flatbed trucks, even with help through the Lend-Lease program, let alone the mass-production of an even more complicated truck designed in 1939 and canceled because of the German invasion.

Automotive factories could not start assembly of a new, complex, and relatively new design, in the conditions that they could not even keep up with simple production models. It is important to note, both of these truck models were standard commercial trucks, with little to no improvements for off-roading or any sort of military specialization. Before the war, the Red Army only had the GAZ-M1 and no off-road trucks.

Side view of the prototype showing off the impressively low profile to a good extent. Note the tarpaulin and muzzle cleaning rod.

The GAZ-68/KSP-76 was also doomed through its design. The use of wheels would have given it faster speeds on good terrain, but most of the western Russian terrain was flat plains and forest, with poor road connections. This is not to take into account the harsh conditions of thick winter snow or deep muds, where even tracked vehicles could struggle. The supply of tires before and during the war was also a big issue for the Red Army. While the situation to some extent improved during the war, they still relied on imported tires for around 33% of their needs.

In modern eyes, a wheeled vehicle might seem superior, as we now have many roads and good infrastructure, plus more advanced technologies, but this was Russia in 1943. The GAZ-68 was simply not compatible with Soviet military doctrine, industrial capabilities, and the terrain of Eastern Europe.

Compared to the SU-76, the GAZ-68 was far cheaper to build and maintain, was 54 cm lower, but with similar protection levels and firepower, in addition to the pros and cons of a wheeled chassis. Whether the KSP-76 was an improvement over the SU-76 is up to debate, but it clearly was not enough to justify the changing of truck production lines to a new vehicle this late into the war.

GAZ-68/KSP-76 illustrated by Pavel Alexe, funded through our Patreon Campaign

GAZ-68 / KSP-76 specifications (Source: TsAMO)

Dimensions (L-W-H) mm 6,350 / 2,050 / 1,550
Total Weight, Battle Ready 5.39 tonnes
Crew 3 (Commander, Driver and loader)
Propulsion X
Speed X km/h
Range X km
Armament 76 mm gun ZiS-3 M1942 Regimental gun (662 m/s muzzle velocity)
Ammunition count 54
Maximum speed, km/h 62.5
Average speed on a paved road, km/h 49.3
Average speed on an unpaved road, km/h 21.2
Engine GAZ-203 (with an aluminum head) outputting 85 hp
Fuel type and range KB-70 or B-70 fuel,
140 liters for 430 km range
Armor (frontal hull, fighting compartment), 7-16 mm
(Sides, rear hull and fighting compartment), 4-7 mm
Total Production 1 prototype

S. Lopovok, Inventor and Rationalizer, No 12,
Zaloga, Steven J., James Grandsen Soviet Tanks and Combat Vehicles of World War Two
A.V. Karpenko. Part 1. Light self-propelled artillery installations  Domestic self-propelled artillery and anti-aircraft installations
Солянкин А.Г., Павлов М.В., Павлов И.В., Желтов И.Т. Отечественные бронированные машины. XX век. Том 2. 1941-1945
TsAMO & GABTU archives (from A. Tarasov)

Red Army Auxiliary Armoured Vehicles, 1930–1945 (Images of War)

Red Army Auxiliary Armoured Vehicles, 1930–1945 (Images of War), by Alex Tarasov

If you ever wanted to learn about probably the most obscure parts of the Soviet tank forces during the Interwar and WW2 – this book is for you.

The book tells the story of the Soviet auxiliary armor, from the conceptual and doctrinal developments of the 1930s to the fierce battles of the Great Patriotic War.

The author not only pays attention to the technical side, but also examines organizational and doctrinal questions, as well as the role and place of the auxiliary armor, as it was seen by the Soviet pioneers of armored warfare Mikhail Tukhachevsky, Vladimir Triandafillov and Konstantin Kalinovsky.

A significant part of the book is dedicated to real battlefield experiences taken from Soviet combat reports. The author analyses the question of how the lack of auxiliary armor affected the combat efficacy of the Soviet tank troops during the most significant operations of the Great Patriotic War, including:

– the South-Western Front, January 1942
– the 3rd Guards Tank Army in the battles for Kharkov in December 1942–March 1943
– the 2nd Tank Army in January–February 1944, during the battles of the Zhitomir–Berdichev offensive
– the 6th Guards Tank Army in the Manchurian operation in August–September 1945

The book also explores the question of engineering support from 1930 to the Battle of Berlin. The research is based mainly on archival documents never published before and it will be very useful for scholars and researchers.
Buy this book on Amazon!

Cold War Soviet Prototypes Has Own Video WW2 Soviet Prototypes

Object 704

Soviet Union (1945)
Heavy Self-Propelled Gun – 1 Prototype Built

The SU-152 and ISU-152 were, and still are, well known for their massive guns and impressive claimed capabilities against German tanks such as the Tiger and Panther. That is how they got their nickname “Zveroboy”, meaning beast killer. However, that was more related to propaganda than their actual usefulness as tank destroyers. Their massive 152 mm guns, while very effective if they hit the target, were rather inaccurate at long range, slow to aim and to reload, and limited in traverse by their mounting in a superstructure. These guns were not well suited for a tank destroyer. The SU-152 and ISU-152 were not, in fact, tank destroyers, but assault guns, meant to help Soviet attacks break down enemy defenses and strongpoints. Yet, for assault guns, their protection was more often than not, quite lacking. With the start of production of the Kirovets-1 (Object 703, or better known as IS-3), the opportunity arose to improve the “Beast Killers”, now focusing on protection. This vehicle was to become the Object 704 or Kirovets-2. It is also called ISU-152 model 1945 in Russian literature, however, it is likely that the Object 704 was never referred to as such in the short life it had, and could be a modern name, possibly invented at Kubinka, according to Russian historian Yuri Pasholok.

Despite the success of the ISU-152, its weak armor, tall silhouette, and inconvenient muzzle blast made the Soviets seek a replacement. Ironically, they never got one and the ISU-152 served decades after WWII. Source: Pinterest


Due to the problems of the ISU-152, proposals came as early as 1944 from GABTU (Main Directorate of Armed forces) to the SKB-2 plant to upgrade the vehicle, however, little materialized. Then, work started on a new IS tank- the Kirovets 1 (IS-3).

There were also plans to modernize the gun on the ISU-152 as well. In 1943, the GABTU Artillery section stated that the 152.4 mm ML-20S howitzer was not suited for use on a self-propelled gun. The issues on the ML-20 naturally reflected on the battle performance of the ISU-152. An example was the TsAKB slotted muzzle brake kicking up a lot of dust, almost blinding the gunner after firing, and more importantly, revealing the vehicle’s position.

Thus, the GABTU put out a series of requirements for the modernization of the weapon. Firstly, this included the removal of the muzzle brake, changes to the breech, and improvements to the recoil system. OKB-172 was assigned to develop the upgrade by the 13th of January, 1944, headed by M. Tsirulnikov. The new gun was to be named ML-20SM, M standing for modernized. Blueprints were ready by the 1st of March of the same year and, by the 10th of March, the prototype was built in Factory No.172. The very next day, firing trials were undertaken, but after the 33rd shot, testing was halted due to poor operation of the new breech. Further tests were made through March until the 14th of April when it passed the test for rapid consecutive firing of 60 shots, which it fired in 39 minutes. While that might seem like a lot, the initial firing time estimation for them was 60 minutes (1 round per minute), the gun averaging 1.5 rounds per minute. Testing continued into May, the gun firing a total of 249 rounds, out of which 196 were with high explosive charges (for direct firing). The average rate of fire over the entire testing period was an impressive 2.9 rounds per minute. Factory testing of this gun continued until September 1944. Due to the high rate of fire and no muzzle brake, it was decided on the 2nd of October to mount the gun inside an ISU-152. Consequently, the gun was shipped off to Chelyabinsk, but, when it arrived in the middle of October 1944, it was unfinished! At the end of 1944, the GABTU stated that the gun needed urgent work and that factory No.172 workers should be sent to ChKZ. This only happened by mid-February 1945, when the battlefield was different and the IS-3 was approaching mass production, making the ISU-152 chassis archaic.

The massive muzzle blast made concealing the vehicle virtually impossible after firing. It also blinded the crew, so following the shot and keeping track of the target was a challenge. Source: Weapons of Victory

In fact, ChKZ had started working on an SPG based on the Kirovets-1 at the beginning of 1945. It received the name Kirovets-2. The chief engineer and designer was L.S. Trojanov.

A letter from Engineer-Lieutenant Colonel Markin, a representative of the GABTU in ChKZ, was sent to GABTU chief Engineer-Lieutenant Colonel Blagonravov on this topic. It stated that the Kirov factory (SKB-2 to be precise) was working on a Kirovets-1 based SPG, stating its armor thickness level and other features, namely that it used the same transmission, running gear and engine as the Kirovets-1. Most interesting is that, according to the letter, work on the prototype started on the 1st of February, 1945. The letter was sent 10th of February, 1945.

The Kirovets-2, later named Object 704, was an attempt to fix the main issues with the ISU-152, yet created more problems and was plagued by bureaucratic wrangling. Source:

ChKZ also announced S.P. Gurenko, chief designer of Factory No. 172, saying that SKB-2 was working on such a vehicle. This led to engineers from No. 172 coming over to Chelyabinsk between the 14th and 20th of February. During this time, SKB-2 had sent the blueprints of the Kirovets-2 over to Factory No. 200 as well. Also in mid-February, the hull of the SPG was ready in ChKZ.

On the 3rd of March, a meeting was held on the topic of improving the Kirovets-2. The main issue brought up was fitting the ML-20SM, originally built for the ISU-152, into the Kirovets-2. The gun had been sitting for quite a few months in a hall somewhere in ChKZ. Other points discussed were further increasing the armor and thickening it from 100 to 150 mm (3.9 – 5.9 inches) and replacing the panoramic sight with a Hertz sight from a 76 mm Mod. 1943 ZiS-3 gun, as it was smaller. The telescopic sight was also changed for a smaller TSh-17. The traverse mechanism was altered and, most importantly, it was decided to give the Kirovets-2 a co-axial DShK heavy machine gun, mounted on the right side of the main gun.

The hull of the Kirovets-2 was ready in spring, but the gun was not mounted until halfway through June 1945. This delay was caused by bureaucratic disputes regarding the serial production of the ML-20SM gun. The tank became the Object 704, yet the Kirovets-2 name stuck with factory workers.

Layout and Design

The design of the Kirovets-2 was unique, having little resemblance to previous Soviet heavy SPGs. It still had a frontal mounted casemate, where the turret and pike nose of the IS-3 used to be. Due to the aim to improve the armor protection to the same level as the IS-3, the armor plates were thickened and angled throughout the casemate. On the ISU-152, the gun mantlet was a large frontal weak spot, yet on the Object 704, it was the thickest part of the tank. Interesting to add is that the bottom of the side casemate angled inwards a lot more than it appears to. The almost flat triangle shape part of the side superstructure is actually just a thin sheet of metal.

Although the IS-3 chassis was used, there were still some changes made. Namely, the engine plate was different and the exhaust pipe layout was the same as on the Object 701. It is unclear if this was done to save pieces for the production of the IS-3 or it was intentionally designed as such. An additional small construction detail is the use of several track types, satisfactory for a prototype built in a short period of time. There were 86 tracks per side, each track was 650 mm wide and they were connected by a single pin. The engine was the same V-2-IS engine, producing 520 hp, and the running gear and transmission were kept the same. The transmission was a multi-disc dry friction clutch. The gearbox was a 4+1 dual stage (high/low) manual, for a total of 8 gears forwards and 2 in reverse. The brakes were still planetary rotation mechanisms.

The hull is often said to be identical to that of the IS-3, but the exhausts and engine plate design are different. Note the thinness of the triangular-shaped side plates on the hull can be discerned here. Source: Yuri Pasholok

Despite the external differences, inside, the Object 704 was very similar to the ISU-152. It still had a crew of five; driver, gunner, commander, loader, and breech operator. The heavily angled sidewalls caused major internal ergonomic problems, namely storage for the huge two-part ammunition, which weighed 48.78 kg (107 lb) for the AP and 43.56 kg (96 lb) for the HE, no easy task to load in a tight space. Sacrificing crew comfort and ergonomics for protection was quite common in the late war and post-war Soviet tank doctrine.

Object-704 during testing. The extreme angles of the fighting compartment can be seen. Source: Pinterest

The vehicle’s silhouette was much shorter than that of the ISU-152, now being only 2,240 mm (88 inches) tall, but kept the same width.

Main Armament

The modernized ML-20SM lacked a muzzle brake, which improved the visibility and kicked-up less dust after firing. However, the recoil grew considerably, namely by 900 mm, so a recoil brake was added. The gun had +18° of gun elevation and a shockingly poor -1.45° of depression. The horizontal traverse was not much better at a very limited total of just 11° (5.5° on each side). The new gun fired the same two-part HE weighing 43.56 kg (96 lb) and AP ammunition, weighing 48.78 kg (107 lb), and had very similar ballistics to the standard ML-20S. The HE rounds had a muzzle velocity of 655 m/s, while the AP had 600 m/s. The gun could hit a 2.5 to 3-meter tall target reliably from 800 to 1,000 meters (874 to 1,093 yards), but had a direct fire range of 3.8 km (2.36 miles) and an indirect fire range was 13 km (8 miles).

When conducting indirect firing, the Hertz panoramic scope was taken out through the gunner’s hatch. The practical rate of fire is contradicting and ranges from one to a bit under three rounds a minute. A quick reload was not necessary for such a self-propelled gun, especially considering the terrible ammunition count inside the Kirovets-2; just 20 (19 according to the trial report, although the extra round could be loaded to be 19 +1)) rounds. These were placed on both sidewalls of the fighting compartment, and the charges were placed on the right wall and underneath the breech.

View of the breech of the ML-20SM. Note part of the loader’s tray to the bottom left and the coaxial DShK machine gun to the right of the gun. The manual traverse can also be seen, which was to be operated by the breech operator. Source: Yuri Pasholok

Secondary Armament

The vehicle was equipped with two 12.7 mm DShK heavy machine guns, one coaxially mounted and one on the roof, with 300 spare rounds of ammunition inside (600 according to Kubinka). There was a chute for the ammunition belt to slide over the main gun and into the machine gun.

The roof-mounted DShK was for anti-aircraft use and was mounted on a rotating ring over the loader’s hatch. The ring could swivel over and next to the hatch. The machine gun itself could also pivot on its mount. A collimating K-10T sight was mounted on the gun for easier aiming against aircraft.

For the defense of the 5 crew members, they were equipped with PPSh or PPS submachine guns. Some F-1 grenades could also be mounted on the sidewall, between the commander and breech operator.


The Object 704 had a crew of 5; driver, commander, gunner, loader, and breech operator. They would communicate with each other with a TPU-4F intercom, having a headset and a microphone. This was essential, as the crew sat quite far away from each other and communication was key in coordinating aiming and directions. Every crew member had his own entry and exit hatch on the roof of the vehicle.

The driver was located higher up in the hull than in the ISU-152, by 600 to 700 mm. Consequently, he did not have his own hatch in the front plate, instead, his vision relied on the single movable MK-4 periscope in his hatch, on the roof. As could be anticipated by such an arrangement, this was not enough, giving the driver rather poor vision when buttoned up. He was, however, also able to open the hatch (by sliding it to the side) and stick his head out in non-lethal environments. To control the tank, he had two mechanical tillers. To his right was the gearshift and the shift for the high/low gear ranges. On a good note, the driver no longer sat next to a large fuel tank, like on the ISU-152, which was good for morale.

The gunner sat behind and to the right of the driver, on a seat attached directly to the gun. There, he had the elevation control hand crank, as well as the trigger, his Hertz panoramic sight, and the 2.5x (other sources claim 4x) magnification TSh-17 sights. This sight was adequate for firing up to 1500 meters (0.93 miles). As previously mentioned, for indirect firing, the gunner’s hatch had to be opened and the sight raised through it. Both sights were illuminated for conducting nocturnal firing. Directly under the breech block was a floor-mounted escape hatch, for a total of six hatches.

The commander was on the opposite side of the driver, also having just one MK-4 periscope for external vision. He was responsible for the radio, placed right in front of him, on the frontal armor plate. This radio was a 10PK-26 radio, connected to the 24 volts onboard power transmitter. The frequency was 3.75 Mhz to 6 Mhz, with a wavelength varying between 50 to 80 meters. While stationary, the range was between 20 to 25 km, and it decreased slightly while on the move. The radio also allowed for communication on two fixed frequencies, simultaneously. The coaxial machine gun was also his responsibility, most likely having to fire it as well. Yet the traverse of the main gun was controlled by the breech operator and elevation by the gunner, so aiming would have been a coordination challenge.

Handling the massive shells was done by the loader. The shells were stacked on the side walls. He was also assigned operation of the anti-air DShK on top of his hatch. To aid him in loading, he had a loading tray, attached to the gun. A round would be rested on it until it was ready to load again. This meant that the loader did not have to hold the round until the breech was open again, a little but crucial detail considering the round’s weight. There were 12 rounds on the wall next to him, while the other 7 were on the other side, by the breech operator, and were a challenge to extract.

Perhaps the most curious crew member position is the breech operator. It is important to note that the breech design was quite ancient and could not open automatically. The breech operator would open the breech while the loader was manhandling the rounds into the gun. Then he would close it. He could assist the loader with charge amounts as well. This was done to decrease the strain on the loader, as it was no easy feat.

While testing reports were quite satisfied with the positions of the crew, a few issues were brought up. The angled sidewalls made storage of ammunition complex and accessing them was cumbersome. Let alone moving them out and into the gun, considering their weight. The elevation of the driver’s position also brought drawbacks, namely, he would bounce around when the tank was moving on poor terrain. This was strenuous on the driver. To boost morale and improve living conditions, two fans were placed behind the gun, to ventilate and remove toxic fumes, as well as a couple of dome lights.


As aforementioned, the engine was a V-2-IS outputting 520 horsepower. An ST-700 electrical motor, outputting 15 hp (11 kW), was used for starting the main engine. In cold winters, two compressed air cylinders were used to start the engine. These were located by the driver’s feet. An NK-1 diesel fuel pump was used, with an RNA-1 regulator and carburetor. Air filtering was done by a multicyclone air filter. There was also a heater, used to heat the engine in cold winters, but also the fighting compartment. A total of three fuel tanks were in the vehicle, two in the fighting compartment and one in the engine bay, for a total of 540 liters (143 gallons). Two (90 liters each) external fuel tanks were on the engine deck. These were not connected to the fuel system and were meant to be dismounted when entering battle. The engine allowed the tank to reach a top speed of 37 to 40 km/h (23 to 25 mph). The fuel range was around 180 km (112 miles).

The rear of the Object 704, where differences in the engine plate compared to the IS-3 can be seen, such as the tow hook placement. Source: Warspot


Protection was one of the main focuses of the Object 704 project. All armored plates were welded with heavy sloping all around the casemate. The front plate was 120 mm thick, angled at 50°. The lower plate was 100 mm (or 120, sources are conflicting or might imply there might have been different thicknesses proposed) angled at -55°. The mantlet had two layers of rounded 100 mm cast armor. The side was 90 mm angled at 15° from the side. Even the rear casemate armor was 80 mm at 21°. The tank was immune from the front to the 88 mm PaK 43 L/71 gun of the Tiger II, which it never got to fight. Despite this thick armor, the vehicle still had an acceptable weight of 47.3 tonnes (52 US tons).

This was a very well protected vehicle. The thin (3 mm) sheets “hiding” the heavily sloped lower casemate armor can be seen. Source: Soviet Heavy SPGs, 1941-1945 page 38.

Test results

The SPG was finished by mid-June of 1945. It was sent to Moscow Factory No.37, from where it was taken to the state proving grounds at Kubinka. Originally, testers noted that the fighting compartment was cramped but later changed to praises for the commander’s and driver’s stations and their placement. The People’s Commissariat of Armaments asked to move the Object 704 to the Leningrad Artillery Research Experiment Range, to test the gun and artillery capabilities. Despite this, the vehicle was still sitting in Kubinka. A test program letter for the ML-20SM was also sent in July 1945. It was only in August when tests were approved but only began by September because Factory No.172 engineers did not arrive at the testing grounds. They finally arrived by the 24th of September, only to leave a few days later, leaving behind only an engineer which did not have authorization for any testing work! This outright comical timeline of bureaucracy delayed the testing of the Object 704 by six months. By the 13th of November, Kuznetsov and chief designer Nazarov finally arrived from plant No. 172. Testing was done from October until the 13th of November, through which 65 shots were fired for indirect fire and 244 shots for direct fire.

A letter summarising the results and opinions after tests was published.

  • Loading tray: No complaints other than the corners should be rounded, to make passing between the loader’s station and the breech operator easier.
  • Sights: The TSh-17 was comfortable and in a good position in relation to the gunner’s eye. The offset of the sight was negligible after 40 shots (it is safe to assume after more shots, the offset would be noticeable).

Fighting compartment notes

Several interesting remarks were made in relation to the superstructure and the design of the fighting compartment.
– The gun mantlet had no access port for the much-needed recoil brake. This meant that measuring the hydraulic fluid and releasing air was impossible.
– The hole below the gun mantlet (for depression of the gun) accumulated water.
– The sloping on the side walls made stowing ammunition difficult and complicated. Making the walls vertical was suggested.
– The headlight was mounted on a solid mount. Because of this, it shattered during firing trials. A movable spring stand was recommended.
– The commander’s position was praised, it was put facing forwards and the new hatch made battlefield observation easier and more effective.
– Both the gunner’s and driver’s stations were praised and deemed as an improvement over previous heavy SPGs.
– The loader’s position was actually considered spacious. The report stated that taking out the 12 rounds next to him could be done with ease. However, the 7 rounds on the opposite wall were noted to be hard to reach and load.
– In contrast, the breech operator’s station was noted to be cramped, especially when the gun was traversed to the left, bringing the breech to the right. Extracting the 16 propellant charges to the right side of the tank was not ideal due to the tight space. The other 4 charges beneath the gun were impossible to take out in combat conditions.

Other conclusions were:
– Wear on the barrel and muzzle velocity drop was typical, considering the caliber of the gun. After 309 rounds (244 of which with maximum charge), muzzle velocity dropped by 0.8%.
– The muzzle brake simplifies production and improves observation of the target after firing.
– Recoil brake performance is satisfactory, but the problems with access to it still stand.
– No unexpected wear or deformation occurred on the gun.
The gun had no malfunctions with the exception of failure to extract shell casings that had been used several times (as much as 10 shots).

Conclusion and fate

The Object 704 had clear advantages over the ISU-152. These included the lack of a muzzle brake, improved protection, and position of the driver and commander. The issues that were found, could, and most likely would have been addressed, if it would have entered production. The tank’s entry in service was hindered by bureaucracy and failure to get it to testing. The loss of time meant that the IS-4 was nearing serial production, making the IS-3 and a SPG based on it obsolete. With hindsight, the story of the IS-4 is, arguably, even worse. Another heavy self-propelled gun would not be built until the Object 268, based on the T-10, which had a similar fate to the Object 704.

The single prototype built survives today at Kubinka, where it was brought for testing in 1945. Source: World War II Wiki

You can also watch a walk around of the exterior and interior of the vehicle, made by “The Chieftain”, Nicholas Moran, here 

Object 704 specifications

Dimensions (L-W-H) 8.53 x 2.24 x 3.15 meters

(28 x 7.3 x 10 feet)

Total Weight, Battle Ready 47.3 tonnes (52 US tons)
Crew 5 (Commander, Gunner, Driver, Loader & Breech operator)
Propulsion V-2-IS diesel engine, 520 hp
Speed 40 km/h

(25 mph)

Armament 152.4 mm ML-20SM 2-part ammunition howitzer

co-axial 12.7 mm DShK heavy machine gun

Anti-air 12.7 mm DShK heavy machine gun

Armor Hull armor:

Front top plate: 120 mm at 50°

Front bottom plate: 120/100 mm at -55°

Top side armor: 120 to 90 mm at 15° degrees

Side inwards angled bottom armor: 90 mm at 60°

Side hull: 90 mm at 90°

Rear: 60 mm at 46°

Top: 30 mm

Belly: 20 mm

Total Production 1 prototype
Illustration of the Object 704 by Pavel Alexe, based on work by David Bocquelet, funded through our Patreon campaign.

Heavy SPGs 1941-1945, Soliankin, Pavlov, Palov, Zheltov
Zveroboy, Mikhail Baryatinsky
Heavy SPG, A.V. Karpenko

Has Own Video WW2 Soviet Prototypes

Object 217, PPG

Soviet Union (1940)
Mobile Machine Gun Nest – 1 Prototype Built

The Soviet-Finnish War of 1939-1940, more commonly known in the West as the ‘Winter War’, saw many one-off vehicles being designed to help the Soviet Red Army overcome the determined Finnish defenses. Many of these never made it to the front to be tested under fire.

One example of such a unique design was the Object 217, also known as the Podvizhnoye Pulemyotnoye Gnezdo or mobile machine-gun nest.


As the Soviet Red Army set about reorganizing itself in January 1940 due to its ineffectiveness in the opening month of the conflict, many meetings were held to discuss how best to tackle the various obstacles encountered in Finland.

One complaint was the lack of tank/infantry coordination. More often than not, the Soviet tanks would charge ahead and smash through the Finnish lines. The Finns used this to their advantage by allowing the tanks to pass and then reoccupying their positions soon after and shooting at the following infantry. To help counter this, several designs for infantry shields and tank-drawn armored sleds were produced by the various factories of Leningrad (modern-day St. Petersburg). These allowed for sections of infantry to be towed in relative safety to the Finnish lines in order to secure them before the Finns returned.

Clad in snow-suits and well prepared for the harsh climate a Finnish light machine gun position firing upon advancing Soviet troops at Kollaa. Source:SA-Kuva

However, this was not always successful. Once the Finns understood the method of delivery, they used their valuable anti-tank guns to target the towing tanks, or they adapted their defensive positions in order to provide incoming fire as quickly as possible.

Another solution

Another idea was to design a machine-gun-armed tankette that could support advancing infantry. The already existing T-27 was too tall, too weakly armored, and performed too poorly in the snow. As the fighting was in full swing, a quick, cheap design was needed. The task of designing such a vehicle was given to Special Design Bureau No. 2 of the Leningrad Plant of Experimental Engineering No. 185, also known as the Kirov Plant, under the leadership of Josef Yakovlevich Kotin. Kotin created a team under Leading Engineer L. E. Sychev and given the project designation of ‘Object 217’. It was soon called Podvizhnoye pulemyotnoye gnezdo or mobile machine-gun nest by the team.

The finished Object 217 prototype. Source:-

The design team quickly produced technical drawings based around a four-speed motorcycle engine with simple suspension. By the beginning of March, a prototype was ready and sent for factory testing. Another four prototypes were also being constructed for trials. The assessors were initially impressed with the vehicle as it fulfilled all the requirements laid out in the request. Even so, the design had numerous drawbacks that called into question its usefulness.

The two Degtyaryov DT machine guns had limited arcs of fire, the crew positions caused discomfort and fatigue within short periods of time, and the armor was seen as too weak when coupled with the limited mobility. However, none of these deficiencies was the reason for not adopting the machine. On 13th March 1940, the Winter War came to a close and there was no longer a need for such a niche vehicle. As a result, the Armored Directorate of the Red Army canceled the project. All the prototypes were scrapped.



The Object 217 used a single-piece of rolled armored steel to form the main body of the vehicle. To this were welded and riveted the side and rear armor. The designers wanted to minimize the silhouette. To do this, they created an oddly laid out fighting compartment. The two crew members sat with the two access hatches on top of the vehicle open during transportation, but when in combat they would adopt a prone position, lying face down inside. At its maximum height, the Object 217 measured only 55 cm. To allow the crew to see, they were each provided with simple periscope devices that protruded from the roof and covered in an armored box. However, this meant that the two crew members had no visibility to their sides and rear.

The commander was seated on the right side, with the driver on the left side of the vehicle.

A headlight was present on the right-hand side, while a smaller rear light was also present on the left-hand side.

A model of Object 217, showing the layout of the hull. The added side vision slit is not seen in the photo of the real vehicle. Source:

Engine and Transmission

To keep the costs down, a PMZ motorcycle 16 horsepower two-stroke, 2-cylinder, air-cooled petrol engine was used for this vehicle. This allowed for limited self-propulsion which was not an issue, as the deployment of the vehicle involved being towed behind a T-26 until it reached the Finnish defenses and then unhooking itself. The transmission was a three-speed gearbox seated next to the engine. A simple friction clutch system controlled by a set of levers was used to control the movement of the vehicle. The factory tests gave a top road speed of 18.5 km/h and a cross country speed of 7 km/h. Due to the large size of the engine in comparison to the internal space available, it was necessary to create an armored box at the rear of the vehicle with several access panels.

The trials also showed that the Object 217 was capable of climbing 30-35 degree inclines and could clear trenches 1 meter wide. It could also wade through streams and puddles so long as they did not exceed half a meter in depth. How this would have translated to the Karelian Isthmus though is not known. The relatively low ground pressure was ideal for getting across the snow but the varied terrain, especially at the specially selected areas of the Mannerheim Line, would probably be taxing on the vehicle.

The same model, clearly showing the engine box. Source:

Running gear

The Object 217 was given a very simple running gear. This consisted of four large cast spoked road wheels which were fixed to rigid axles. To provide power, a drive wheel, about half the size of the road wheels, was installed at the rear. The front road wheels could also turn like the wheels on a car, bending the track in order to allow the vehicle to steer, in a similar style to the later Light Tank Mk VII Tetrarch. To lower the amount of dust and snow thrown up by the tracks, the front and rear had protruding fenders.

The lack of suspension was one of the biggest drawbacks to the design. It put a considerable strain upon the crew, especially under combat conditions that required them to lie down. After only a short while, the assessors reported fatigue which would only make the combat effectiveness of the vehicle worse.

Armor Protection

For the type of vehicle and time, the Object 217 boasted an acceptable armor layout. The front consisted of a rolled single piece of armored plate measuring 20 mm in thickness. The sides were 10 mm thick rolled single pieces that were mainly welded upon the body, with a few rivets in the rear of the vehicle to help strengthen it. The roof and underside were 8 mm thick rolled armored plates. The advanced use of single rolled pieces of armored plate coupled with a heavy reliance on welding gave it a great amount of protection against small arms and shell fragments.

The assessors did express concern about the armor’s ability to withstand anti-tank gunfire or near hits by artillery but this was less about the armor and more about how the limited mobility meant an overreliance upon the armor for protection.

An original document showing two views of the Object 217 vehicle. The upper photograph is already known, but the lower one shows the hatches open, giving information about the upper part of the vehicles. Source:


The original directive stipulated that the vehicle had to be armed with a machine gun. This was due to its main task being to keep the Finnish defenders suppressed. The design team added two Degtyaryov DT machine guns in ball mounts which would be aimed using the attached sights. These allowed for 20 degrees of travel in all directions, but this was limited more due to ergonomics within the hull rather than the installations themselves. The sides of the hull contained racks for 25 pan-type magazines, giving a total ammunition amount of 1,575 rounds per gun. In order to allow the crew to maintain operation without the need to clear spent shell casings, each gun mount had a specially designed bag that connected to the side ejection port.

Analysis of possible use

It is not sure how Object 217 would be deployed but some speculations can be made based upon the tactics used by the Soviets during the second offensive phase of the Winter War.

Possibly, after a heavy artillery bombardment upon a section of the Finnish line, a squadron of 12 T-26s would set off, 2 towing Object 217s and 4 towing Sokolov sleds (each carrying 5 Soviet soldiers). As the tanks neared the line, they detached the tow cables and the soldiers advanced to the trenches. The Object 217s would take positions on the flanks, suppressing the Finnish defenders. With these types of tactics, which were deployed during the second offensive phase, but with T-26s taking the role that the Object 217s would have played, it would allow for more tanks to be pushed into the breakthrough and still have the Infantry secure the position. The vehicles could then use their own power to cross the trenches and be ready for any Finnish counterattack.


The Object 217 was a unique vehicle designed for a unique situation. As the Soviet advance stalled by the indefatigable Finnish defense in December 1939, the Soviet Red Army needed any solution to breakthrough. The solution of an armored machine gun position attached to the infantry was a quick fix as it negated a lengthy rework of the current Soviet tactics. The final vehicle produced, however, was inherently flawed as a design. With such extremely limited visibility and a very uncomfortable fighting position for the crew its combat potential was small. The crew would become rapidly tired and the mobile and adaptable Finns would no doubt have quickly learned of its serious limitation and come up with tactics to exploit its weaknesses using their mobility to get around it. With the end of the Winter War the serious deficiencies of the design were never shown by actual combat but the fact that this design was not repeated again is perhaps the strongest indication that this unique vehicle was not an effective solution to breaching well prepared enemy defences. To do that would rely on a far better use of coordinated operations and flexible vehicles supported by artillery – something the Soviets repeatedly failed to manage during the Winter War.

The very small Object 217 mobile machine gun nest was a very peculiar vehicle, very low, with the engine in a small box at the rear. Illustration by Yuvnashva Sharma, funded by our Patreon campaign.


Komolyets, Maxim. Tanks in the Winter War: 1939 – 1940 (Operations: Scandinavia 1939) (Leandoer and Ekholm (April 14, 2009))