Shooting at Shadows
At the start of 1941, Soviet anti-tank artillery evolved simultaneously in several directions. The most promising weapon was the 57 mm F-31, later indexed ZiS-2. This gun was developed at factory #92 under the direction of V.G. Grabin. In parallel, a "powerful 76 mm AT gun on the USV base" was developed, with the factory designation F-26. It was plagued with difficulties. Due to problems with the recoil brake, the gun was redesigned several times. Finally, in early January of 1941, under Grabin's initiative, an 85 mm anti-tank gun was also developed. It was based on the mount of the experimental 95 mm F-25 divisional gun with lengthened trails. In January, it fired 225 shots.
On March 11th, 1941, the chief of the Red Army General Staff Intelligence Directorate, Lieutenant-General F.I. Golikov, prepared a special report "On the direction of development of the armed forces of Germany and changes in its status". According to this document, German industry began constructing three new types of tanks. The most powerful one, called "Type VII" allegedly weighed 90 tons and was armed with a 105 mm gun. The military treated this information very seriously. The T-150, which was supposed to enter production as the KV-3, was cancelled. Instead, a new vehicle was developed on the basis of the KV-220. The new KV-3 would have a 107 mm gun, have armour about 120 mm thick, and weigh 67-68 tons. In addition, KV-4 and KV-5 tanks were developed in parallel.
The NKB must develop and produce by that date 3000 armour piercing shells with tracer, phlegmatizer, and decopperer in the propellant."
The tank destroyer mentioned in the decree was to be developed in parallel with the SU-B-13 and "212" SPG. According to project documentation, development of the SU-B-13 began, a project was drafted, tactical-technical requirements were made, and the project stalled. The production of the 212 SPG ended during construction of the hull. Unlike these two, the project of the tank destroyer did not even reach the tactical-technical requirements stage. However, the "powerful 107 mm corps gun" made it further.