The appearance of the German Panther tank in the summer of 1943 convinced the Red Army to make a serious upgrade of its tank force for the first time since 1941. Soviet tanks needed bigger guns to take on the growing numbers of Panthers and the few Tigers. A stopgap upgrade to the KV series was the short-lived KV-85. This was a KV-1S with a new turret designed for the IS-85 or IS-1, 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. Later, the KV-85 will be equipped with a stronger 122mm D-25T cannon in a new designed turret, same gun and turret used on the IS-2, wich become the KV-122. It was manufacted on the second half of autumn 1943. The idea of this modernization made was necessity to strengthen the armament of the Soviet Tanks. The KV-122 was used mostly for adjustment of fire of the new 122mm gun (initially called D-25T) in field combat conditions. Later the D-25T gun was installed in almost all the JS-tanks. Practically the KV-122 were not in serial production, but the maintenance sections of the combat units made local modernization of the damaged KV-85 tanks while installing the JS-tank turrets on their hulls. Official, only one prototype was made in 1944 and was never taking in service. However, this is FHSW!