The T-34-85 is the Soviet Union's advanced medium tank, with the "85" denoting its 85mm main armament.
The appearance in 1942 of the Tiger I spurred improvements to the T-34 design, as its 76.2mm medium-velocity gun was ineffective against the heavy armor of the Tiger. At first the Soviets experimented with mounting a high-velocity 57mm ZiS-4 gun on the existing T-34, but this robbed the tank of any anti-infantry capability. With the new German Panther tank and up-gunned and up-armoured Panzer IVs entering the field, the Soviets abandoned plans for a new T-43 tank in 1943 and instead began producing the T-34-85, mounting thicker armor and a larger turret with an 85mm main gun. Although still inferior to the Panther in antiarmor punch and protection, the T-34-85 was produced in much greater numbers. First appearing on the battlefield in 1944, T-34-85 production in the last two years of the war totaled 22,559 tanks. The T-34-85 had a long career after the war; North Korean examples would face US M4A4 Shermans in Korea and as late as the 2000s examples can still be found in some Third World armies.
The T-34-85 is a formidable unit in the game; although inferior in antitank firepower and protection to the Tiger and Panther tanks it is cheaper, faster, and more agile. The 85mm HE shells fired in the antipersonnel role are quite destructive to infantry and fortifications. As a T-34, this tank keeps it's speed and cost advantage to anything equivelent, but unlike the T-34-76, it's just good enough that being under par no longer hindes it's effectivness, as it's gun deal more then enough damage to destroy heavy tanks and the front armor will stop anything left over from mid game interactions.
Although it can be used as a raiding tank to great effect, the good old T-34-76 is 1.5 times cheaper and can be thrown away due to lack of other uses in later stages of the game, while T-34-85's are a valuable asset and usually form the backbone of the soviet army