Russian BT Series – AFV Weapons 37

Designed in the early 1930s, BT fast tanks for Bystrokhodny Tank (from the Russian, reads. Tank Velocity), played a major role in the development of the Soviet armoured force. They were the first models of tanks available in large numbers that allowed the development of mechanized doctrines. Although these doctrines were brought into dispute and forgotten just before the beginning of the German invasion, they paved the way for those later who used the descendants of the Bt, the T-34.

Source: Wikipedia