WW2 Soviet Heavy Tank Prototypes

Object 222 (T-222/KV-3/KV-6)

Soviet Union (1941)
Heavy tank – Partial Mock-up Built

Even before the T-150 heavy tank entered trials in January 1941, several issues had already been noted and a new turret was designed. Nonetheless, this turret never left the drawing board. A second attempt was made during and after the T-150 trials, and the tank was named Object 222. After impressing the military and state officials, it was named KV-3. The excitement was short-lived, however. In April, heavier tanks, like the Object 223, were designed, and this latter project would eventually get the name KV-3 as well. The Object 222 was then meant to enter production in June 1941, under the name KV-6, but, due to the German invasion of the Soviet Union, this never happened.

The T-150

The KV-1 heavy tank would officially enter production in February 1940, 9 months after the original request for production. Even so, by July, only 32 of the pre-series KV tanks were built, prefixed with the “U” index. The tanks had design issues, along with technical and production problems. The pressure from Stalin to adopt these unfinished tanks grew, and, in June 1940, with the “The Stalin Task”, the Council of People’s Commissars of the Soviet Union would order the increase of the yearly production quota of the KV to 230 units of both variants (130 standard KV-1 and 100 KV-2s with 152 mm howitzers). The Leningrad Kirov Plant (LKZ), barely able to keep up with the previous production rate, was ravished. Corners had to be cut in order to streamline and speed up production, while the tanks were still being tested and improved on the go. This cutting of corners would later come to bite the Soviet officials and factory designers in the back, as the KV-1 would prove to be unreliable and cumbersome on the battlefield.

The desire for heavier tanks based on the KV-1 appeared in May 1940, and by 17 July, the Main Directorate of Armored Forces (GABTU) and the People’s Commissariat of Heavy Engineering requested four new tanks from LKZ, more specifically the SKB-2 design bureau. Out of these four tanks, two were to pack 90 mm of armor, of which one armed with a 76 mm gun and one with an 85 mm gun. The other two were to have 100 mm of armor and also be equipped with a 76 mm and 85 mm gun respectively. The latter would become the T-220.

For the 90 mm armor tank with 76 mm gun, the chief designer, Military Engineer L.N. Pereverzev, part of the SKB-2 design bureau, was assigned to design it by August 1940. The new tank was indexed T-150, but the Object 150 and KV-150 names were also officially used. It was to be based entirely on the KV-1 in production, with only the necessary changes made. In order to add the extra 15 mm of armor all around the tank, it was necessary to equip it with a new engine, namely the 700 hp V-5 from Plant No.75. As the thickening of the armor was done outwards, the internal layout and components position of the KV-1 were kept the same. Reinforcements were added to the suspension to better deal with the extra mass, which reached 50.16 tonnes, compared to the 44 tonne KV-1 (autumn 1940). Lastly, and perhaps the largest external change on the T-150, was the addition of a large commander’s cupola, equipped with 6 periscopes and one rotating PTC periscope.

The T-150 was a premature attempt at improving the armor of the KV-1, which was already excellently well armored.
Source: Warspot, colorized by Johannes Dorn

The first prototype was to be built and delivered to LKZ by the Izhora plant by 1 October, but due to overloading difficulties caused by the KV-1 production, the prototype was only delivered by 1 November. During November, after analysis by its designers, a new turret for the T-150 was designed, that would fix certain problems annotated, like the poor commander’s position to the right of the gun. In the new turret, the commander was moved to the back, inside the turret bustle, where he would have a better overview of the battlefield, with 8 periscopes instead of 6, and better communication with the crew. Another problem fixed was the removal of the gunshield above the mantlet, which on the T-150 prototype was poorly made and restricted gun depression. Despite these promising changes, it did not go past the blueprint stage.

Testing of the T-150 would begin on 14 January 1941 and end in February. During this period, several significant issues were discovered. Firstly, the T-150 weighed 50.16 tonnes, over 2 tonnes heavier than the 48 tonne threshold imposed by the GABTU. Secondly, the experimental V-5 engines would prove to be a complete disaster. The chief designer of Plant No.75, T. Chuptakhin, who was present at the trials, was not able to guarantee the operation of the engines installed on the T-150 and T-220 tanks. The T-150 would only operate for 24 hours or 199 km before its engine broke down. It was noted that when driving in high gears (3rd and 4th gear), the injected oil temperature would spike after just 5 minutes even in outside temperatures of 9-12º Celsius.

The turret would prove problematic as well, despite the issues originally being noticed in November. The commander’s cupola was too tall for observation while sitting down, but too low when standing up, forcing the commander to semi-squat in a very straining position. The other crewmembers in the turret were not spared of problems either. The loader, sat behind the commander and to the right of the gun, would be restricted from lifting shells from the left wall by DT machine gun ammunition boxes. The vast majority of the main gun shells were stored in small boxes, which were hard to open, cutting the loader’s hands and getting stuck on one-another. This decreased the rate of fire to 1-2 rounds per minute when loading from the boxes (from 5-7 rounds per minute maximum). Lastly, the gunshield above the mantlet was badly designed and only allowed for 3º of gun depression, instead of the 6.5º intended.

All in all, the T-150 performed as expected considering the rough circumstances, and many of the issues could be roughed up. Despite this, the GABTU and People’s Commissariat of Heavy Engineering were not satisfied with the result and demanded that the turret and engine problems be fixed.

The November 1940 sketch for an improved turret for the T-150. This turret would become the basis for the turret of the Object 222.
Source: Warspot


Before the T-150 trials were even finished, a second attempt at improving the turret was made. Like the first time, the commander’s position was moved to the turret bustle, with a more streamlined cupola, which dropped the PTC rotating periscope but maintained the eight periscopes, as opposed to the T-150’s six. Other changes included the casting of the gun mantlet for faster production, removing the side turret wall gun port and decreasing the size of the gunshield. One of the more controversial changes was the adjusting of the side and rear wall armor to vertical angles, as opposed to 15° inwards. Otherwise, the design would use the same hull as the original T-150. The tank was indexed Object 222.

After review of the project by the GABTU and state authorities, the People’s Commissariat of Defence and the Central Committee of the Communist Party proposed accepting Object 222 into service and giving it the name KV-3. The name KV-3 had previously been used when describing the T-150. The question of propulsion was also raised, but after a commission formed on 21 February, Plant No.75 had to figure out the issues with its engines and make them usable by 10 April. To ensure that the engine would not overheat again, the cooling system of the Object 222 was reworked as well.

The Object 222 was still armed with the 76 mm F-32 gun, but with the same gun being introduced on the KV-1, it seemed like it would quickly become redundant. Thus, it was also proposed that the Object 222 (KV-3) was to be rearmed with the much more potent 76 mm F-34.

On 3 March 1941, a commission was formed, consisting of Military Engineers 2nd Rank I.A. Burtsev and I.A. Shpitanov, Military Engineer 3rd rank Kaulin, LKZ director I.M. Zaltsman, SKB-2 director J.Y. Kotin, director of LKZ 1st dept. A.Y. Lantsberg and NII-48 research institute engineers V. Dalle and A.P. Goryachev. The goal of the commission was to further assess the Object 222 and prepare it for prototype production. The commission reviewed the drawings of the tank as well as a wooden mock-up of the turret mounted on the hull of the KV-1. It was here that the lack of an angle on the side and rear plates was deemed as an issue, decreasing the overall armor protection. Other issues noted was the lack of an entry and exit hatch on the commander’s cupola and vulnerability of the pericopes from damage and enemy fire.

Nonetheless, the commission agreed on producing a turret as per the above in order to have it ready for testing by 1 April. Yet the commission would expect that, by the time of mass production, the turret walls would be angled again. According to the three representatives from LKZ, Zaltsman, Kotin and Lantsberg, the reasons for implementation of vertical walls were:

  • Improving crew working conditions;
  • Improving connections between the plates, especially for the roof plate;
  • Easier manufacturing.

Additionally, they claimed that the sloping brought no true advantages either. Mathematically, the equivalent armor thickness of a 90 mm plate angled at 15° is 93.17 mm, an insignificant gain considering the production complications.

After the commission, on 15 March, the Council of People’s Commissars of the Soviet Union and the Central Committee of the Communist Party gave decree No. 548-232§, which imposed that LKZ had to switch mass production to the KV-3 (Object 222) in August, with 55 units built in the first month, increasing to 105 in September, 110 through October and November, and 120 units in December, for a total of 500 KV-3 tanks in 1941.

The date of delivery was also pushed back after LKZ’s ‘complaints’, and the first prototype was to be delivered by 1 May, and testing to begin on 15 May. To meet this deadline, the Izhora plant had to deliver the experimental turret by 1 April, with LKZ having to deliver drawings of the experimental turret on 20 March, drawings of the hull by March 25 and drawings of the production turret by 10 April. Plant No.203 to deliver the KRSTB radio set and Plant No.69 to deliver optical sights for the DT machine guns.


The Object 222 (T-222/KV-3) was just a T-150 hull with a slightly modified turret. In turn, the T-150’s hull was just a KV-1 hull with a new engine and minor dimension changes due to the thicker armor. The frontal upper plate consisted of two parts, an angled ‘hood’ and a flatter portion, right in front of the driver and radio operator. On it was the headlight, driver’s vision port, and a 7.62 DT machine gun in a ball-mount. Above, on the top deck was a service hatch for the two crewmembers. The running gear consisted of a frontal idler, large rear sprocket, and 6 steel rimmed wheels, sprung by torsion bars, with three return rollers.

The general armor profile was of 90 mm all around, with the exception of the turret roof, which was 40 mm thick, and hull deck, which was 30 mm. With the new turret, the weight of the Object 222 was expected to be slightly higher than that of the T-150, at 51 to 52 tonnes.

The side drawing of the Object 222, armed with the 76 mm F-32 gun, circa February 1940.
Source: Yuri Pasholok


The new turret differed greatly from the T-150’, but was heavily inspired by the November 1940 T-150 turret upgrade. The gun mantlet was a two-part cast type, and the gunshield was shorter, for improved gun elevation and depression angles. The design of the turret walls was altered as well, with larger flat side and rear plates and potentially a rear turret door, like on the KV-2 and T-220, though this is unconfirmed. The rear-facing 7.62 mm DT machine gun mount was kept, though the ball-mount design was changed as well. Other minor changes to the turret included strengthening around the gun mantlet side-front plate connection and the replacement of side gun port and vision slit with a small hatch.

The most important change was the relocation of the commander, to the back of the turret. The position of the T-150’s commander was noted as an issue already in November 1940, thus the first turret upgrade design also placed the commander in the back. Likewise, the trials of the T-150 criticized the position of the commander and suggested moving him to the rear. However, after the commission analysis of the Object 222 turret, it was not deemed as ideal. Additionally, the lack of an entry-exit hatch for the commander and no protection ring for the periscopes were also deemed as an issue. To fit the commander in the turret overhang, a large groove was made along the connection between the turret ring and the turret overhang bottom plate, to allow the commander to sit on.

Internal cutout view of the Object 222. Note the position of the F-32 gun ammunition in the turret bustle.
Source: Stalin’s Supertanks IS-7


The crew consisted of 5: commander, gunner, loader, driver, and radio operator. The commander sat in the turret bustle, from where he could communicate with the loader and gunner. For vision, he had a cupola with 8 periscopes. He would also operate the rear facing machine gun, should the situation call for it. The gunner sat to the left of the gun, and had his primary gun sight and a PTC rotating periscope for general vision. A second fixed periscope was placed on the side of the turret, like on most KV tanks. The loader sat to the right and rear of the gun, and would load shells from both sides of the turret walls and those stowed in the hull floor. He was no longer responsible for the rear-facing machine gun.

The positions of the crew in the hull was unchanged from the KV-1, with the driver in the center and the radio operator to his left. The radio was a KRSTB, an early version of the 10-RT radio, but it was possible to install the standard 71-TK-3 radio.

Commander’s position on the November 1940 turret upgrade of the T-150. Some of the changes were incorporated into the Object 222.
Source: Warspot


The engine of the Object 222 was to remain the V-5 engine, as on the T-150, but in a functional form and with a redesigned cooling system. The V-5 engine had been developed at Plant No.75 by boosting the V-2K 600 hp engine, which itself was an already boosted and unreliable variant of the V-2. The V-5 was a four-stroke 12-cylinder diesel engine outputting 700 hp. The fuel tank had a 700 liter capacity, offering the tank a range of 250 km or 10 work hours. Maximum speed was a mere 35 km/h on road and off-road, 15 to 20 km/h. The tank had a warranted distance between major breakdowns of 2,000 km.


Initially, the main armament was to remain the 76.2 mm F-32, as on the original T-150 and which just began incorporation on serially produced KV-1s, replacing the L-11 gun. But during discussions in February, it was proposed to rearm the Object 222 with the much more potent 76.2 mm F-34. The tank carried 114 shells for the 76 mm gun and 2900 rounds in 46 drums for the DT machine guns. The main difference between the F-32 and F-34 guns was the muzzle velocity and penetration. For example, the same shell, BR-350A (APHE) had 615 m/s muzzle velocity in the F-32 and 662 m/s in the F-34. Likewise, the OF-350 (HE) had 615 m/s muzzle velocity on the F-32 and 680 m/s on the F-34. The F-34 gun was mounted on the T-34 tank in early 1941, with the KV-1 adopting it only much later as the ZiS-5 gun.

F-32 F-34
Caliber (mm) 76.2 76.2
Muzzle velocity (m/s) 615 662
Shell weight (kg) 6.3 6.3

The tank was armed with two 7.62 DT machine guns, one in the hull for the radio operator and one in the back of the turret. The KV-1 and T-150 also featured a coaxial machine gun, but it was dropped on the Object 222, as the commander was moved and due to the new gun mantlet.


Between 7-9 April, the LKZ heavy tank development programs were altered, as the need for more powerful heavy tanks was assessed. The KV-3 name would be given to a new tank, based on the up-armored chassis (120 mm frontal armor) of the Object 221, and named Object 223, as well as receiving an entirely new turret armed with the 107 mm ZiS-6. Furthermore, a 100-tonne tank was also requested, with 170 mm of frontal armor and also armed with the 107 mm ZiS-6 and was named KV-5 (Object 225). The LKZ factory was still meant to build a prototype and begin prototype production by June, but with three heavy tank developments ongoing simultaneously with tight deadlines. Based on the production quota report for LKZ, 500 KV-3 (Object 223) tanks should have been built from August 1941 to the end of the year.

The KV-3 (Object 223). Despite also being named KV-3, the Object 223 was a serious upgrade over its predecessor.
Source: Warspot

On 5 May, Marshal G.I. Kulik and Lt. Gen. Y. Fedorenko came to the Central Committee of the Council of People’s Commissars of the Soviet Union, requesting the switch to the KV-6 (Object 222) as opposed to the KV-3 (Object 223). Historian Maxim Kolomiets also mentions here that the KV-6 was also armed with a flamethrower with 15 rounds (10 liters) and that the vehicle was actually the T-150, though that is improbable.

The situation worsened on 22 June 1941, when the Axis forces began Operation Barbarossa, the invasion of the Soviet Union. Thus, much of the military’s focus shifted to producing, maintaining, and improving existing tanks. Furthermore, by September, German forces were approaching the city of Leningrad and many SKB-2 engineers were evacuated or placed into military maintenance battalions. Those evacuated were sent to the Chelyabinsk Tractor Plant (ChTZ) which was renamed ChKZ (Chelyabinsk Kirov Plant) after this move. Work on the KV-4 and KV-5 would not resume, but the KV-3 would continue to see slow development until December, when it was finally canceled.

The Object 222, (KV-6) would be ordered to start production at ChTZ on 1 January 1942, with LKZ and NKTM officials providing a prototype, while ChTZ sends a team to LKZ to establish the technical details of the design and prepare for its production.


The first KV-3, the Object 222, was just a T-150 with a new turret. Unlike its predecessor, it was much more short-lived, damned by the design and developments of much heavier KV tanks. With hindsight, the Object 222 was a genuinely good design on paper, and a mature improvement of the KV-1. Sadly, the Object 222 remains overshadowed to this day by more ‘exciting’ designs, like the T-220 and Object 223, the latter KV-3. Only a turret mock-up was built, which was likely destroyed during the war.

Object 222. Illustration by Pavel Alexe.

Object 222 (T-222/KV-3/KV-6) Specifications

Dimensions (L-W-H) (approx.) 6.760 x 3.330 x 3.010 m
Total weight, battle-ready 51 – 52 tonnes
Crew 5 (Commander, gunner, loader, driver, radio operator)
Propulsion V-5 12-cylinder diesel, outputting 700 hp.
Speed 35 km/h
Suspension Torsion bar, 6
Armament 76.2 mm F-32 or F-34
3x 7.62 mm DT machine guns
Armor Front/sides/rear of hull and turret: 90 mm
Top/Belly: 30 to 40 mm
No. Built Partial mock-up


Breakthrough tank KV – Maxim Kolomiets
Supertanki Stalina IS-7 – Maxim Kolomiets
Victory Tank KV Vol.1 & 2 – Maxim Kolomiets
Constructors of Combat Vehicles – N.S. Popov
Bronevoy Schit Stalina. Istoriya Sovetskogo Tanka (1937-1943) – M. Svirin
About the forgotten creators of Soviet armored power. ( – S.I. Pudovkin
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: KV Gun Upgrades – Peter Samsonov
Tank Archives: Missing Index: KV-6
№ 189. Resolution of the Council of People’s Commissars of the USSR and the Central Committee of the All-Union Communist Party (Bolsheviks) No. 548-232ss “On the Production of KV Tanks for 1941”

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