The Kliment Voroshilov (KV) tanks were a series of Soviet Red Army heavy tanks, named after the Soviet defense commissar and politician Kliment Voroshilov. The KV series were known for their extremely heavy armour protection during the early part of World War II, especially during the first year of the invasion of the Soviet Union. A stopgap upgrade to the KV series was the short-lived KV-85 or Objekt 239. This was a KV-1S with a new turret designed for the IS-85, mounting the same 85 mm D-5T gun as the SU-85 and early versions of the T-34-85; demand for the gun slowed production of the KV-85 tremendously and only 148 were built before the KV design was replaced. The KV-85 was produced in the fall and winter of 1943-44; And production of the KV-85 was stopped by the spring of 1944 once the IS-2 entered full scale production.