Even before the KV-1 entered combat against the Wehrmacht, there were noticeable problems with it, and replacements were drawn up in 1940, beginning with Object 150, which was nothing more than a KV-1 with a commander’s cuppola.
The next project to be drawn up was Object 220, which had more of everything. It blimped to an enormous size, with the chassis now long enough to mount seven pairs of road wheels, though it could easily fit eight. The turret was shaped like that of the KV-2, though not as tall, and mounted an 85mm gun. A secondary machine gun turret was also mounted on top of the main turret, which the Soviets had already experimented with on the T-100. Because of the great size of Object 220, it was clear that it could mount a much larger main weapon, with fairly minor changes. Thus, not only was it a basis for the KV-3, but also a template for many of the KV-4 projects.
After the successful tests of the 107mm ZiS-6 cannon on the KV-2, several new heavy and super-heavy tanks were designed around it. The KV-3 was the first of such designs to be built, but the 107mm was not a requirement for it. Three designs were submitted for the KV-3 project, all based on the long chassis of Object 220: Objects 221, 222, and 223. The latter was chosen, using a sloped, elliptical turret with commander’s cuppola and armed with the 107mm cannon. A single prototype each of both Object 220 and Object 223 were constructed in 1941, but destroyed when the Wehrmacht attacked Leningrad, one of them by a direct hit from a 150mm howitzer.
Object 150 (T-150)
Object 220 (KV-220)