IS tank family

The IS Tank (IS in Cyrillic "ИС", meaning the Joseph Stalin or Iosif Stalin in Cyrillic "Ио́сиф Ста́лин") was a series of heavy tanks developed as a successor to the KV-series by the Soviet Union during World War II. It was named after Soviet leader Joseph Stalin. The heavy tank was designed with thick armour to counter the German 88 mm guns, and carried a main gun that was capable of defeating the German Tiger and Panther tanks. It was mainly a breakthrough tank, firing a heavy high-explosive shell that was useful against entrenchments and bunkers. The IS-2 was put into service in April 1944, and was used as a spearhead by the Red Army in the final stage of the Battle of Berlin.

Design and production

KV-85 and IS-85/IS-1

The KV-1 was criticized by its crews for its poor mobility and lack of any heavier armament than the T-34 medium tank. It was much more expensive than the T-34, without having greater combat performance. This led Moscow to order a portion of KV-1 assembly lines to shift to T-34 production, which fed into fears that KV-1 production would be halted and the SKB-2 design bureau led by Kotin closed. In 1942 this problem was partially addressed by the KV-1S tank. The KV-1S used thinner armor than the original, making it lighter and faster. It was competitive with the T-34, but at the cost of no longer having the heavier armor. Production of the KV-1S was gradually replaced by the SU-152 and ended completely on April 1943.