|Engine Power (hp)||600|
|Speed Limit (km/h)||34|
|Standard Shell Penetration (mm)||149 - 201|
|Standard Shell Damage||210 - 350|
|Rate of Fire (rounds/min)||6.1|
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.