KV-1S, 13th Guards Heavy Tank Regiment, Bryansk Front. Frustration with the KV-1’s weight and slow speed led to the design of the KV-1S, which was several tons lighter and featured an improved powertrain. Most importantly, the design included a new turret with a three-man crew, and the tank commander no longer had to serve as a gunner or loader. The tank retained the KV-1’s rear-facing turret machine gun to sweep any attacking enemy infantry off the rear deck, but it was to be used by the commander when necessary and did not have a dedicated crewman. The KV-1S featured a 360-degree vision cupola, but oddly it did not have a hatch, leaving the loader’s hatch the only functional one on the turret. The 13th Guards Tank Regiment, along with several other KV-1S units, lost heavily when sent into frontal assaults against German antitank guns in the early stages of Operation Kutuzov on July 13. By April 1943, due to its vulnerability and expense, KV-1S production was halted and the Soviets concentrated on developing the T-34/85 and new series of Stalin heavy tanks.