In June 1945, the Design Bureau of Factory No. 100 started designing the second tank designated IS-7. Compared to the preliminary variant, the Object 257, armoring and mobility requirements increased. In September 1945, four draft designs were developed for the tank that was still called the IS-7. The Object 259 was a project with the KCh-30 engine and an electromechanical transmission. In 1946, several variants of the vehicle's machine gun armament were developed, including several types of turret-mounted rear anti-aircraft guns with remote aiming.