On March 11th, 1941, Soviet intelligence reported on the production of new German heavy tanks. The largest of them, Type VII, allegedly had a mass of 90 tons and was armed with a 105 mm gun. Soviet high command took this report very seriously. Design work started to create a worthy opponent for German heavy tanks. The result of this work was the creation of several unusual projects: KV-4 and KV-5.
The information was partially correct, as the VK 65.01 project was finished in June of 1940, and it really was indexed Pz.Kpfw. VII. One of the tanks was to be armed with a 105 mm gun, but only 20 calibers long. The design of the 36 ton VK 36.01 started in the middle of 1940, which was indexed Pz.Kpfw. VI Ausf B. This was the mass of the "Type V" mentioned in the report. Information on real vehicles ended up mixed with hearsay. This hearsay created such a stir in the Soviet Union that heavy tank designs were radically revised.
It is thought that the flywheel of superheavy tanks started spinning on April 7th, 1941, when USSR SNK and CC of the VKP(b) decree #827-345ss was issued. In reality, everything started two weeks before. Having studied the intelligence report, GAU assumed that the 90 ton tank was armed with a tank version of the 105 mm Flak 39. This gun was purchased in 1940 by a Soviet commission. Trials demonstrated that a 130 mm armour plate provided adequate defense from this gun.
On March 21st, 1941, tactical-technical requirements were composed for the tank that would be named KV-4. Its mass was estimated at 70-72 tons. The front of the hull and the entire turret would have 130 mm of armour, the sides of the hull would have 120 mm. The armament would consist of a 107 mm F-42 (ZiS-6) gun and three machineguns. A note at the end of the document said that two tanks should be made, one with a 76 mm gun (the ZiS-5 with 3-K ballistics) and one with a 107 mm gun. The tank would store 70-80 107 mm shells. A 1200 hp engine was specified as the power plant. As a temporary measure, an 850 V-2SN engine was acceptable. With the more powerful engine, the maximum speed of the tank was rated at 35 kph.
By March 27th, the draft of the decree "On the production of experimental prototypes of heavy tanks" was ready. According to it, both heavy tank prototypes were due on November 1st, 1941. The blueprints would be ready at the Kirov factory by July 17th, and Izhor factory had to have the hulls and turrets ready by October 1st. Factory #92 would deliver one 76 mm ZiS-5 and one 107 mm ZiS-6 by September 1st.
As for the engines, plans were awaited within ten days for V-2 and M-40 based designs. The V-2 was the V-2SN, but the second engine is a much more interesting proposal. This aircraft based engine was produced at the Kirov factory. Its stock power output was 1000 hp, but a supercharged 1500 hp M-40F also existed.
The sixth point in the decree contained ideas about transporting the tank by rail. The People's Commissariat of Supply Lines (NKPS) could only offer four-axle platforms with a capacity of 60 tons. Obviously, for a 70 ton tank, this was not enough.
Anyway, by April 7th, the situation changed drastically. Instead of the KV-3, a reworked T-150 with a mass of 50 tons, a new tank would be built, with the same index, a mass of 68 tons, 120 mm of front armour, and a 107 mm gun. The approach to the KV-4 changed as well. Its mass increased to 75 tons, and the armour could potentially increase to 140-150 mm. The sides thickened to 125 mm. The deadline was moved: it was now necessary to prepare the model and technical project by June 15th and the turret and hull were expected by August 15th, 1941.
This wasn't all. Instead of a KV-4 wit a 76 mm gun, decree #827-345ss instructed the Kirov factory to build a tank that would be an answer to the phantom Pz.Kpfw. VII. As the German vehicle, this KV-5 would have a mass of 90 tons. Its armament and engine would be the same as on the KV-4. The increase in mass was due to the front armour, which was 170 mm thick in the front and 150 mm thick on the sides. The crew of both tanks would be between 6 and 8 men.
According to the decree, the blueprints for this tank were due at the Izhor factory by July 15th, and full documentation with a full scale model was due on August 1st. The Kirov factory would receive a turret and a hull by October 1st, and the tank itself would be finished on November 10th, 1941.
These new requirements meant that if the tank wouldn't have to be made from scratch, the idea would have to be drastically revised. Zh.Ya. Kotin, the director of the Kirov factory design bureau, had a difficult problem that had to be solved quickly.
Zhosef Yakovlevich took the same road as the design bureau of factory #185 when developing heavy and medium tanks in the late 1930s. During development of the 115 and T-100 tanks, several variants were prepared by different groups. Kotin went one step further and included nearly all designers from the factory into the project. For extra motivation, the authors of the more successful designs would be awarded a bonus.
Work started in the middle of April of 1941. The conditions of the contest limited the engineers fairly loosely. The only constants were the engine (M-40), mass (80-100 tons) and the presence of a turret. A multi-turret layout was allowed. The main gun would be a 107 mm ZiS-6, and the military insisted on a secondary 45 mm gun. In total, 27 projects were provided for the contest. The size of this article does not permit to cover them all, so we will discuss the more interesting designs.
N.L. Dukhov was the most successful in this task. Without coming up with any excessive fantasies, Nikolai Leonidovich approached the issue conservatively and expanded the T-220 tank. The hull was somewhat lengthened and widened, increasing the number of road wheels to 8 per side. The turret was also evolutionary, resembling the T-220 turret. The T-220 also donated its commander's cupola (with some changes), equipped with a DT machinegun. The armament, a 107 mm and a 45 mm gun, was combined into a single system.
The mass of Dukhov's tank was 82 tons, the lightest of all KV-4 proposals. The armour was at the levels required by the project, and the maximum speed of the tank was on the order of 40 kph. This design won the contest.
The second place was taken by a collective design by K.I. Kuzmin, P.S. Tarapanin, and V.I. Tarotko (some sources list S.V. Mitskevich instead of Tarapanin). Kuzmin and Tarotko later proved themselves to be talented hull designers. The KV-4 tank proposed by this group was unusual. Its fighting compartment was moved to the back, and the engine was placed in the center. The main gun was placed in a casemate with a wide horizontal range. The 45 mm gun was in a separate turret. The mass of the tank was 88 kph, and the speed was estimated at 36 kph.
The third place was taken by N.V. Tseits. Nikolai Valentinovich was the most experienced designer at the Kirov factory, starting his job in the 1920s, and having a wide variety of vehicles under his belt. Tseits' design was progressive and conservative at the same time. The second gun was discarded, as he considered it unnecessary. Tseits' design is characterized by a tall turret, allowing the vertical placement of one-piece 107 mm shells. In theory, this layout would greatly ease the loader's job. In order to compensate for the tall turret, the hull was made as low as possible. A "step" separated the fighting and engine compartments.
Another project received praise, designed by A.S. Yermolayev, who proposed two variants. The first 95 ton KV-4 had two turrets. The main one had a 107 mm gun, and the second, placed in front of it, had a 45 mm gun. The second variant was the same, but the 45 mm gun turret was missing, taking 5 tons of weight with it. Yermolayev must have remembered the SMK, the development of which he was in charge of. It's worth noting that at least five other authors used the same layout as Yermolayev.
The heaviest design was by G.V. Kruchenyh, who later designed the turret for the IS-3. Like Kuzmin, Tarapanin, and Tarotko, the engine in this design was moved forward. The tank had two turrets, one on top of another. A commander's cupola with a machinegun made up the third level. Krucheniy's KV-4 weighed a whopping 107 tons. The idea of turrets stacked on top of one another came up in five other projects.
At last, let us mention the KV-4 designed by N.F. Shashmurin. Nikolai Fedorovich indexed the KV-4 and KV-5 projects "BS", which he decoded as "a madman's nonsense" (bred sumashedshevo). No one can describe what he came up with better than the man himself.
"Having received the task to design a multi-turreted cyclops among the other leading designers of the bureau, I, without the enthusiasm about that condition (just think, we just rejected the "supermarket" SMK) I made a "knight's move", rejecting turrets altogether, and doing what I once did for the KV-1, installing the M-10 howitzer in a caponier structure, a casemate. Since we just made a super-heavy KV-3 tank, I didn't think too hard about a new one. I took off the turret and repeated my previous work, a high power SPG, installing Grabin's 107 mm gun. I explained in a note that, if necessary, the gun could be removed and replaced with an infantry squad. This modification was not allowed to enter the competition, as it violated the conditions: not enough armour, mass outside the 80-100 ton range, no turrets. In order to avoid a conflict, I made a compromise. Maintaining that a superheavy cannot be a tank, I added the necessary protection, reaching about 90 tons. I kept the main gun in a casemate, but added a KV-1 turret on the roof. I.M. Zaltsmann liked the design (due to its "reasonable universality", as he called it) and I received a second place award, 1000 roubles. That was nice, I bought a fur coat for my wife."
On May 9th, 1941, the contest winners were annouced. Dukhov received 5000 roubles for first place. Kuzmin, Tarotko, and Mitskevich received 3000 for their second place project. Tseits, Yermolayev, and Sychev received 2000 roubles each. Shashmurin received 1500 roubles.
After that, work on the KV-4 went slowly. According to the decree, the project was due in mid June, but judging by the correspondence sent, not much progress was made towards that goal. Things got to the point that Marshall Kulik himself intervened and demanded that work speed up. No one knows how much effect that had, since his letter was dated June 12th, and the war started ten days later.
Another stakeholder, the NKPS, was doing much better. GABTU and NKPS actively exchanged mail regarding railroad platforms for new tanks since spring of 1941. The goal at first was 72 tons, but in April, the numbers changed to 80-100 tons. GABTU ordered 200 of these platforms for 1941 and 1500 for 1942. Unlike the tankers, the railroaders completed their mission. In 1941, production of six-axle 120 ton platforms began, with length and weight capacity to spare.
As for the KV-5, almost no work was done until June of 1941. According to Zaltsmann's letters, there was an idea to announce a prize for the winning KV-5 design as well, but that idea was dropped. Kotin's competition was rejected and more successful KV-4 designs were reused. As Dukhov's design was already being worked on and the front-engined tank was too progressive, Tseits' KV-4 was selected. Nikolai Valentinovich was appointed as the lead designer. Other engineers from the KV-4 contest were involved in the project: Kuzmin was designing the hull, Sychev the turret and gun mount. Fedorchuk, the most experienced designer, was given the suspension.
The KV-4 and KV-5 were in an odd place. On one hand, GABTU's position was that the KV-3, the work on which was progressing at full throttle, was a temporary solution, and would be replaced in 1942 by the KV-4 or KV-5. Which design would win would be a matter settled by competitive trials.
On the other hand, the KV-4, approved in May, had nearly no documents completed. The same could not be said for the KV-5, work on which continued even after the start of the war and the order to cease work. Even the manufacturing technology was changed. The last blueprints were dated August of 1941, when the Germans were already near Leningrad.
As mentioned above, the KV-5 was based on Tseits' KV-4. The idea of a tall turret and short hull was expanded upon and adapted to mass production. The "step" in front of the turret was removed. The driver received a personal casemate, and the hull gunner got a mini turret. Because of this, the front of the hull was only 920 mm tall. Second, the circular shape of the main turret was revised. The front armour grew to 180 mm, making it invincible to any gun of that era.
Battle of Phantoms
The development of the KV-4 and KV-5 is usually seen as a senseless waste of time and money. This is largely true. Even if the war did not start in 1941, it is doubtful that these tanks could enter mass production. However, where there's smoke, there's fire. The mistakes made by Soviet intelligence have a basis in fact.
Study of Bunderarchiv documents shows that, in March of 1941, Kripp began production of the 15 cm K. L/40 Sfl., or 149 mm self-propelled gun. In the fall of 1941, this project turned into 15 cm L L/40 fur VK 70.01. Yes, this is the very same VK 70.01, better known as Lowe or Pz.Kpfw. VII. The mass of this tank was also 90 tons, and one of the armament variants was a 105 mm gun. Perhaps this is the Pz.Kpfw. VII that intelligence discovered. In any case, this is not the VK 70.01 that is widely known now, as sloped armour was only used in Germany after the fall of 1941 when the Germans became familiar with the T-34.
Original article by Yuri Pasholok.