In March 1941, the Kirov and Izhora Plants were tasked with working on shielding the KV-1 tank. The final versions of drafts were reviewed on May 13, 1941, and blueprints were approved on June 19. The front of the vehicle needed reinforcing, as did the turret and sides of the hull. The Kirov Plant had already assembled three shielded vehicles by June 16, 1941, and production was underway until late July of the same year.