The KV-85 was designed by a design bureau led by Lieutenant-Colonel Kotin. He split the bureau into two and each team had different specifications to design for. One of the teams was told to improve the KV series as a stopgap for a new heavy tank. This design was to become the KV-85.
The KV-85 was based on the KV-1-S's hull. The armor was increased to 4.3" / 110 mm.
Some KV-1Cs / KV-1s were upgraded in the winter of 1943-44.
With delays in the IS-85 and the front lines wanting new heavier tanks, an initial 148 KV-85s were manufactured in the autumn of 1943. At the start of 1944 all production ceased in favor of the IS series.
The KV-85 had the same 85 mm D-5T gun installed that was to be installed in the IS-85. The hull had to be made wider and the 5th crewman was removed to make room for more ammunition.