Comparing: O-I vs. KV-2

Development of the superheavy tank was started after the Battles of Khalkhyn Gol in 1939. The vehicle was designed as a maneuverable fire unit that was unprecedented in scale—its hull alone weighted 100 tons. Only one prototype was built, without a turret and made of construction steel. Trials were discontinued due to the unreliable engine; at the end of 1944, the prototype was scrapped. The 15-cm howitzer was to be mounted on the tank after the assemble.

Heavy assault tank. Developed on the basis of the KV-1 in January 1940, with a total of 334 vehicles manufactured from 1940 through 1941. The KV-2 tanks were used in action in 1941, with most of the vehicles lost the same year.