WW2 Soviet Heavy Tank Prototypes

KV-5 (Object 225)

Soviet Union (1941)
Super Heavy Tank – Partial Blueprints Only

The Soviets were one of the few nations still experimenting with the “land battleship” concept in the late 1930s, with impractical beasts such as the T-100 and SMK. As soon as development seemed like it took a more rational direction with the KV-1 and its heavier counterparts, the T-150 and T-220, rumors of a German 90-tonne tank catalyzed the development of even larger tanks, with the heaviest being the KV-5, weighing 100 tonnes. Work only reached the blueprint stage when its designers were evacuated to Chelyabinsk due to the German forces approaching Leningrad.



In summer 1940, the designers at the SKB-2 design bureau at the LKZ (Kirov Leningrad Plant) began exploring with the idea of increasing the armor and armament of the KV-1, resulting in the T-150 and T-220 (KV-220) prototypes which were tested in winter 1940-1941. However, major reliability issues were encountered with the engines, which delayed the development of both tanks. The situation would change drastically when the Soviet intelligence services put forward a report titled “The direction of development of German armed forces and changes in their state”. On the section regarding heavy tanks, three new German heavy tanks were claimed to be under development:

  • Mark V (36 tonnes, 75 mm gun, 2x machine guns, ≤ 60 mm of armor)
  • Mark VI (45 tonnes, 75 mm gun, 20 mm gun, 3x machine guns, ≤ 70 mm of armor)
  • Mark VII (90 tonnes, 105 mm gun, 2x 20 mm guns, 4x machine guns, unknown armor)

The report also mentioned, based on unconfirmed information, 72-tonne French tanks (possibly the Char 2C, which weighed 69 tonnes) present at the occupied Renault factory, in addition to 60- and 80-tonne tanks being built at Škoda and Krupp.

In terms of actual German heavy tanks under development at the time, the Germans began developing the VK30.01(H) and VK65.01(H) in 1939, and the VK36.01(H) and VK45.01(P) began development in 1941. How exactly the Soviet intelligence concluded that the VK65.01(H) would weigh 90 tonnes is unknown, though unsurprising considering the grave inaccuracies that can be expected from intelligence information. The heavy Panzer VII VK70.01 Löwe project, which varied in weight from 75 to 90 tonnes, could not have been the source for this claim either, as its development only began in late 1941 to early 1942.

The VK65.01(H), which was proposed to be armed with a 105 mm gun. While uncertain, this was likely the basis for the new German tank.
Source: Panzertracts 20-1

Regardless of the truth and origin behind the intelligence report, the Soviet military officials took it seriously. Despite being technically allied nations, the Soviet Union and Nazi German relations were steadily deteriorating, especially considering the proficiency of the German Blitzkrieg in occupying several European countries, including Czechoslovakia, Poland, Denmark, Norway, the Benelux countries, and France.

Likely even more troublesome for the Soviet authorities was the lack of domestic heavy tanks in service and their inferiority to the alleged German tanks. The T-35 was a hopeless remnant from the bygone era of multi-turreted heavy tanks and had little combat value. The KV-1, though very well armored, suffered from the side-effects of being rushed into service, plagued with reliability issues, poor maneuverability, and heavy weight. The T-150 and T-220, while promising on paper, with a 76 mm gun and 90 mm of armor for the former and 85 mm gun and 100 mm of armor for the latter, still required extensive development and could not face the supposed German 90-tonne beast.

The first actions taken by the Main Directorate of Armored Forces of the Red Army (GABTU) were just 10 days later, on 21 March 1940. They had assumed that the 90-tonne tank would be armed with the 105 mm Flak-39, which the Soviets had bought and tested in 1940. Thus, a tank capable of withstanding it would require at least 130 mm of armor. The KV-4, indexed Object 224 or just 224, was created, weighing in at 70 to 72 tonnes and armed with the newly developed 107 mm ZiS-6 gun developed at V.G. Grabin’s Plant No.92 under the name F-42. In terms of propulsion, the 1,200 hp M-40 turbocharged engine was to be used.

Shortly thereafter, on 7 April, with Decree No.827-345ss issued by the Central Committee of the All-Union Communist Party, the development of heavy and super heavy tanks was revised. Firstly, the Object 223 was created, receiving the name KV-3, which had been previously used on the T-150. This new tank was to use the hull of the T-220, though its frontal armor was to be increased to 120 mm and a new turret was to be made, armed with the 107 mm ZiS-6. Additionally, the KV-4 requirements were slightly changed, increasing the minimum weight to 75 tonnes and side armor to 125 mm, amongst other minor changes. Lastly, the largest tank of them all was to be the KV-5, indexed Object 225. It was to weigh 90 tonnes and have 170 mm of frontal armor and 150 mm of side armor. It was to have the same 107 mm gun and M-40 engine as the KV-4. The plans for the KV-5 were to be submitted to the Izhora plant on 15 July and by 1 August full production documentation and a mock-up were to be ready. Lastly, by 1 October, LKZ was to receive a prototype hull and turret of the KV-5 from the Izhora plant.

On 5 May 1941, the Council of People’s Commissars of the USSR and the Central Committee of the All-Union Communist Party signed Resolution No. 1217-503ss, which noted that the KV-3 would be put in production in 1941 as a stopgap design until the KV-4 and KV-5 would be ready for trials in early 1942. The two super heavy tanks would be tested against each other and the winner would enter production.

Proper development of the KV-5 would not begin until June 1941, as up until that point, focus was on the KV-3 and KV-4. The KV-4 was conceived via a drawing competition with nearly two dozen proposals. The winning design by N.L. Dukhov would serve as the basis for the KV-4. After 9 May, when the KV-4 competition results were announced, it was proposed to have a similar competition for the KV-5 as well, with Kotin allocating 11,200 Rubles, however, this was deemed unnecessary considering the similarity between the two tanks. Thus, the third-awarded KV-4 design, created by the very experienced tank designer N.V. Tseits, was chosen for the basis of the KV-5. The reasoning behind why the second place design was not chosen instead was due to its main gun being mounted in the superstructure and not a turret, which deemed it unsuitable and was (possibly) disqualified, though why it was even given second place to begin with remains a mystery.

Tseits’s KV-4 design was characterized by a very low hull, compensated by a large circular turret, with the main gun ammunition stowed vertically. To make room for the driver, bow machine gunner, and engine, large protrusions in the hull were made. Another important feature of Tseit’s KV-4 design was the lack of a 45 mm gun, a feature which would carry onto the KV-5.

Side cutout view of the KV-4 by N.V. Tseits. This design would serve as the general basis for the KV-5.
Source: Stalin’s Supertanks IS-7
Top cutout view of Tseit’s KV-4 design.
Source: Stalin’s Supertanks IS-7

Once Tseit’s design was chosen as the basis of the KV-5, Tseits himself was appointed Senior Designer of the project. The rest of theKV-5’s design team would consist of K.I. Kuzmin (hull), L.E. Sychev (turret and armament), and N.T. Fedorenko (lower hull/chassis). Other engineers working on the KV-5 were A.S. Ermolaev, F.A. Marishkin, S.V. Mitskevich, and M.P. Reznichenko.

Nikolai Valentinovich Tseits, Senior Designer of the KV-5
Source: Wikimedia Commons

The situation for the SKB-2 heavy tanks changed with the Axis’ invasion of the Soviet Union on 22 June 1941, and both the KV-4 and KV-5 were officially canceled with Order No. 253ss of the People’s Commissariat of Heavy Engineering on 26 June. There could have been a variety of reasons for why this was done. The LKZ plant had to now focus on wartime production, maintenance and repair of the KV-1, and the time and funds allocated to these super heavy tank projects were no longer worth it considering the frontline situation.

On the topic of costs, a letter sent on 30 May from the head of production at LKZ, A.I. Lantsberg, regarding the costs of the different heavy tank projects at LKZ mentioned that the total cost of development of the KV-5 would have been around 3,600,000 Rubles, or the cost of around seven KV-1 tanks.

Development cost of the KV-5 (Object 225) [in руб]
Drafts and blueprints 120,000
Models and mock-up 50,000
Technical and functional drawings 380,000
Prototype construction and factory trials 2,200,000*
Military trials 150,000*
Drawing fixes/bug fixes 100,000*
Prototype bug fixes and repairs 600,000*
Sum 3,600,000

* note that the project never reached these stages, thus the project could have exceeded these allocated sums.

Despite the order from the People’s Commissariat of Heavy Engineering, Tseits and his team continued work on the KV-5, with approval from Kotin himself, judging by the fact that he signed the few remaining drawings of the KV-5. So far, only three blueprints remain, one of the turret construction showing the armor plates and their connections (signed by Kotin on 15 August 1941), the hull and armor plate connections (signed by Kotin on 31 July), and the idler along with the tensioning system.

Heavy Burden

In tandem with the development of the super heavy tanks, GABTU turned to the People’s Commissariat of Railways (NKPS) to develop new rail cars capable of transporting the massive tanks. While the Soviets did possess cars capable of carrying 100 tonnes, their width was just 3 m. The 80- to 150-tonne special platforms from the Voroshilovgrad Locomotive Plant could not be used either due to not having a flat platform. Thus, in May 1941, GABTU requested two railcars, one for the KV-4, with a capacity of 85 tonnes, and one for the KV-5, with a capacity of 100 tonnes. To still fit in the standard rail dimensions, the tanks would be transported with their tracks removed, with the hull belly resting directly upon the railcars platform. The wheels of the railcar were to be borrowed from the FD steam locomotive, and be attached to three bogies per side. Based on the amount of such cars that were requested, production plans for the KV-4 and KV-5 was optimistic, with 200 railcars requested for 1941 and 1,500 railcars for 1942.

The 120-tonne transport car meant for the KV-4 and KV-5.
Source: Yuri Pasholok


Tseit’s KV-4 was estimated to weigh 90 tonnes, consequently the KV-5 would weigh even more, at least 100 tonnes. While the large turret and low-profile hull of just 920 mm (the hull was heightened to 1,280 mm at the engine bay) layout was kept, several changes and upgrades were made when designing the KV-5. Firstly, the turret was to be made out of flat armored plates, instead of large cylindrical turret, making production easier. The area for the driver and bow machine gunner was split up, with two domes attached to the hull, giving space to the crewmember’s head and torso, as well as a machine gun turret for the machine gunner, though due to the incomplete blueprints, the exact shape and layout of this arrangement is hard to determine.

The blueprint of the hull shows that the KV-5 was to have eight roadwheels per side, sprung by torsion bars, with the idler mounted at the front, and the drive sprocket at the rear (Tseits’ KV-4 had the sprocket and final drive at the front of the hull, likely for better balance). The idler was of an entirely new design, with several areas strengthened, likely to withstand the immense forces upon it when the tank would move across rough terrain. The engine cooling system intake and exhaust were in the same position as on previous KV tanks. To secure the welds and connection between the thick armor plates, large pin-like bolts with flush heads were used.

The turret had six faces, essentially an enlarged variant of the early KV-2 turret, with the frontal plate slightly angled. While not many details are present in the surviving blueprint, the position of the gun mantlet on the frontal plate can be seen. Additional details such as lifting hooks, gunner’s rotating periscope, four additional periscopes, service hatch (likely for the loader), commander’s (?) cupola, ventilation fan and what is likely the ring for a machine gun turret, on the left side of the turret, can be seen on the blueprints as well. Much like on the hull, the plates were joined with large bolts, however, to further strengthen the joints, hourglass shaped rods were placed in-between the two armor plates.

Blueprints of the KV-5 turret and joints.
Source: Stalin’s Supertanks IS-7
View of the KV-5 hull and joints. While it is mostly incomplete, with many critical details missing, it offers a decent understanding of how the tank would have looked like.
Source: Stalin’s Supertanks IS-7
Oddly enough, the drawing of the KV-5 idler has survived, showcasing the thickening of the central hub for improved durability.
Source: Yuri Pasholok


The crew of the KV-5 was originally noted to be between 6 and 8. An analysis of the blueprints shows that the tank had around 6 crewmembers, with the commander, gunner, turret machine gunner, loader, driver, and hull machine gunner. The exact positions are hard to determine, but it is clear that the gunner sat on the left side of the turret, with a rotating periscope mounted in the turret roof for vision, as well as a fixed MK-4 periscope. Behind him was likely the turret machine gunner, operating the turret machine gun or even helping with loading the main gun. On the opposite side, to the right of the gun, sat the loader. In front of the loader was the tank commander, who would operate the radio and survey the battlefield through his cupola.

In the hull sat the driver and hull machine gunner, on the left and right side of the hull, respectively. However, due to the limited blueprints, much more cannot be said.


The upper frontal plate of the hull was 130 mm thick angled at 50° from horizontal, while the frontal lower plate was 150 mm and angled at 30° from vertical. The side armor was 150 mm and the rear armor was 120 mm thick. The hull deck was 50 mm and belly was 40 mm thick.

The front of the turret was to be 180 mm thick, angled at 15° from vertical. The side and rear armor plates were 150 mm thick and the roof plate 50 mm.


The 107 mm ZiS-6 was the main armament of all KV-4 tanks. It was developed at Plant No.92 by V.G. Grabin in a very short time. Due to its excellent penetration capabilities, it would equip all of the new Soviet super heavy tanks. In summer 1941, the gun was tested on a KV-2, using a KV-3 gun mantlet. There, the excellent power was proven, being able to penetrate 120 mm of armor angled at 30° from 1,600 m.

It is sometimes incorrectly believed that other main armaments were proposed to be mounted on the KV-5, such as the 152 mm ML-20, however, there is no truth to these claims.

Besides the main gun, at least two DT 7.62 mm machine guns were mounted in small turrets, one in the front of the hull and the other on the turret. The design of these turrets is unknown.

The KV-2 used during the ZiS-6 gun trials, fitted with a KV-3 mantlet, June 1941.
Source: Warspot


Initially, the engine for the KV-5 was to be the V12 M-40 diesel aviation engine with four TK-88 turbochargers, for a total output of 1,200 hp. The M-40 had been developed at the LKZ plant just a few months prior and was to also be mounted in the KV-4. However, there were major reliability concerns and so it was proposed that the KV-5 was to be equipped with two V-2K engines instead (2×600 hp). These were the same engines found on the standard KV-1.

The M-40 engine, with two of the four TK-88 turbos visible.
Source: Yuri Pahsolok


Work on the KV-5 finally ceased in mid-August, when the SKB-2 designers were transferred to the ChTZ plant due to German forces approaching Leningrad. Its lighter counterpart, the KV-3, was meant to continue development but worked shifted quickly on developing new, more rational tanks, such as the KV-1S and KV-7, and so the KV-3 was forgotten.

The Soviets would not pursue the idea of such a super heavy tank until the late 1940s, in the form of the 65-tonne Object 705 and 100-tonne Object 718. Both designs were once again born after the discovery of a German tank, this time being the Maus. However, much like their KV-5 predecessor, only partial blueprints were ever made. Only the last variant of the IS-7 (Object 260 mod.1948) would reach an impressive 68 tonnes weight, and although it never entered service, it remains the heaviest Soviet tank ever built.

The fate of the KV-5 designer was not so smooth either. Despite Tseits being one of the oldest and most experienced designers at SKB-2, having worked at the Kazan German-Soviet facility from 1928 and designed a variety of tanks, he was arrested for a second time* (first time in 1930 on “counter-revolutionary” charges which were dropped two years later) and was allegedly sent to Siberia in a gold mine. However, he was brought back to ChKZ by the Commisair of Tank Industry V.A. Malyshev and began work on the KV-13. He died on 19 July 1942, aged 68, still working on the KV-13, after returning from a one-week hunting break.

*some sources claim he was even arrested in 1938.

Filling in the Gaps

There have been several interpretations of how the KV-5 would have looked like. It is often claimed that the tank would have had a machine gun turret in the hull, and while it makes perfect sense, there is no way to know with the current drawings. Furthermore, there are no drawings of the machine gun turrets to begin with. Due to the nature of the project, the KV-5 was shrouded in mystery from the very beginning.

According to historian Yuri Pasholok, SKB-2 designer N.F. Shashmurin, who had designed his own KV-4 variant, mistook the KV-4 by Kruchyonyh as the KV-5 and even mislabelled it, calling it “the ravings of a madman”. A few years and a rough war later, Shashmurin would find himself as the Head Engineer of the IS-7, and pursuing the idea of the “tank of maximal parameters”, designing double barrel heavy tanks. In another Russian publication, Moskvin’s KV-4 design was also mistaken for the KV-5.

Mislabelling of Kruchyonyh’s KV-4 variant as the KV-5, by N.F. Shashmurin. In his defense, this monster was to be even heavier than the KV-5, at 107 tonnes! Shashmurin is known to have strongly advocated against such super heavy tanks, only to become the man behind the IS-7 a few years later.
Source: Yuri Pasholok
Another interpretation of the KV-5 with major mistakes. The turret seems to be largely based on the one from Tseit’s KV-4.

Perhaps the most famous KV-5 interpretation is the one by Viktor Malginov, which while not entirely perfect, offers a good view of the tank and its potential layout. Most interestingly, Malginov speculated that the machine gun turrets would have been much more similar in design to the ones used on the T-220, as opposed to the ones used on Tseits’ KV-4.

Malginov’s drawing of the KV-5. While generally accurate, there are some inaccuracies, such as the idler, the tiny sprocket wheel, and the gun mantlet interfering with the machine gun turret.
Source: Yuri Pasholok
The KV-5, as presented in the game World of Tanks, seemingly also based on Malginov’s drawing.
Source: The Armored Patrol


Setting aside napkin drawings and patents, the KV-5 remains one of the heaviest Soviet tanks ever designed. With up to 180 mm of armor and a strong 107 mm gun, it was a very powerful tank, at least on paper. The Soviets were struggling with the 50-tonne T-150 and 63-tonne T-220, one can only imagine what kind of mechanical disasters the trials of the KV-4 and KV-5 would have brought. Yet none of the planned super-heavy tanks even left the drawing board, as the start of Operation Barbarossa and the quick German advance towards Leningrad rushed a dose of reality to the Soviet officials and heavy tank design turned around, focusing on improving the reliability and mobility of the KV-1 instead, leading to the KV-1S.

The KV-4 (Object 224) by N.V. Tseits, for comparison.
Speculative illustration of the KV-5 (Object 225) with several corrected features, such as the idler. Both illustrations by Pavel ‘Carpaticus’ Alexe.

KV-5 (Object 225) Specifications

Dimensions (L-W-H) 9.5 x 4.2 x 3.2 m
Total weight, battle-ready Originally 90 tonnes, increased to 100 tonnes
Crew 6 – 8 men
Propulsion 1,200 hp diesel V12 M-40 with 4 TK-88 turbochargers later changed to 2x V-2K 600 hp engines
Speed 30 km/h
Armament 107 mm ZiS-6 (F-42)
2x 7.62 mm DT machine guns
Armor Turret front: 180 mm
Turret side & rear: 150 mm
Hull front: 130 to 150 mm
Hull side & rear: 150 mm
Top: 50 mm
Belly: 40 mm
No. Built 0, blueprints only


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One reply on “KV-5 (Object 225)”

I don’t think I have ever seen worse ammunition distribution in a tank than Tseits’ KV-4 design. Literally the majority of the turret’s interior is lined with ammunition.

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