Comparing: IS vs. T29

The IS-1 (IS-85) heavy tank was a thorough modernization of the KV-1. The tank featured the 85-mm D-5T gun. The IS-1 entered mass production in October 1943, but work was discontinued at the beginning of 1944, as the IS-2 (IS-122) tank entered mass production in December 1943. A total of 107 vehicles were manufactured.

Development of this experimental heavy tank started in 1944. The prototype was built in 1947. The vehicle featured the 105 mm T5E1 gun. After the war, the mass production of heavy tanks was deemed unreasonable, and only a few prototypes of this vehicle were built.