To counter the new heavier German tanks the Russian engineers designed a new wider turret able to accept the potent 85mm D-5T gun.
As a stopgap until the arrival of the new "IS-85" the new turret was mounted on the modified KV-1s chassis.
The KV-85 was used to equip a number of Guards heavy tank regiments in October-Novenber 1943 including the 7^th, 11^th, 15^th and 29^th Guards Heavy Tank Regiments.
Each regiment normally had a strength of 21 KV-85 tanks.
Roughly 140 KV-85 were produced in the autumn and winter of 1943-44 and were mainly deployed to the Southern Front where a few of them fell into German hands and one of them, the "white 31", found its way to the "Heereswaffenamt Prüfstelle 6".
Production of the KV-85 was stopped by the spring of 1944 once the IS-1 and the IS-2 entered full scale production.