In autumn of 1941, the Leningrad Kirovskiy Zavod (»LKZ« or Zavod No.100) was evacuated from Leningrad to Chelyabinsk where its equipment and workers, now as part of the new Chelyabinsk Kirovskiy Zavod (»ChKZ« or Zavod No.100), were merged with parts of the Kharkov Diesel Works and the Chelyabinsk Tractor Factory (»ChTZ«) to form the new Chelyabinsk Heavy Machine Factory No.100 (ChZTM), popularly called »Tankograd« (Tank City).
Production of the KV heavy tank was instantly re-established as the Red Army was running out of armour due to the immense tank losses in the summer of 1941.
To increase production output and achieve better armour protection against the upcoming German antitank guns, a new cast turret was developped with an armour thickness of up to 100mm, together with new spoked roadwheels.
The ZiS-5 gun, almost identical to the F-34 gun of the newest T-34 series, replaced the inferior F-32 main gun of the welded turret production series and made the KV a real challenge for its German opponents.