Soviet Medium tank T-34-85

After improved German Panzer IVs with the high-velocity 75 mm (2.95 in) gun were encountered in combat in 1942, a project to design an entirely new Soviet tank was begun, with the goals of increasing armour protection while adding modern features like a torsion-barsuspension and a three-man turret. This new tank, the T-43, was intended to be a universal tank to replace both the T-34 and the KV-1heavy tank. However, the T-43 prototype's armour, though heavier, was still not proof against German 88 mm guns, while its mobility was found to be inferior to the T-34. Finally, although the T-43 shared over 70% of its components with the T-34, manufacturing it would still have required a significant slow-down in production. Consequently, the T-43 was cancelled.

Not only were the weapons of German tanks improving, so was their armour. Soviet firing tests against a captured Tiger I heavy tank in April 1943 showed that the T-34's 76 mm gun could not penetrate the front of the Tiger I at all, and the side only at very close range. A Soviet 85 mm antiaircraft gun, the 52-K, was found capable of doing the job, and so derivatives of it were developed for tanks.^[93][94] The resulting tank gun could penetrate the side armour of the Tiger I from a distance of 800 meters and the turret side from a distance of 600 meters. It was still not enough to match the Tiger, as a Tiger could destroy the T-34 from a distance of 1,500 to 2,000 meters, but it was a noticeable improvement.