Comparing: IS vs. IS-2 vs. KV-4

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.

Built in 1944, the IS-2 (IS-122) heavy tank was a modification of the IS-1. It featured a simple cast glacis plate. Elite Soviet Guards heavy tank regiments used the IS-2 extensively in the assaults on the fortress cities of Budapest, Breslau, and Berlin. These vehicles featured thick white stripes for quick identification by other Soviet tank crews. This vehicle, a tank of the 7th Guards Independent Heavy Tank Brigade, was made famous in a photo taken in front of the iconic Brandenburg Gate in the heart of Berlin.

The project of N. L. Dukhov developed in April 1941. A prototype was to be produced by November 1941. However, the work was discontinued due to the outbreak of the Soviet–German war.