With the German Tiger tank and its lethal 88mm main gun appearing on the Eastern Front, Russia had a reality check that it needed larger calibre main guns on its heavy tanks.
The IS series was under development as a replacement to the KV series, however there was a more pressing need, so an interim fix was to build a new turret for the KV-1S hull to accommodate a larger main gun.
The new turret was fitted with the 85mm D-5T main gun. Accommodation was made available for the storage of 70 rounds of ammunition.
The vehicle entered production the Autumn of 1943 and saw limited service during 1944 as the IS series entered production. Its turret was later adapted for use on the T-43/85 upgrade of the T-34.
The Russian KV-85 Heavy Tank Specifications
Armaments: x1 85mm Main Gun x3 7.62mm MG
Armour: 30 – 110mm steel
Dimensions: Length 8.6m / Width 3.25m / Height 2.9m
Weight: 46 tonne
Engine: V-2 6000bhp Diesel
Top Road Speed: 40 km/h
Range: 250 km