Origins [ edit ] In 1939, the most numerous Soviet tank models were the T-26 infantry tank and the BT series of fast tanks. The T-26 was slow-moving, designed to keep pace with infantry on the ground. The BT tanks were cavalry tanks : fast-moving and light, designed for manoeuvre warfare. Both were Soviet developments of foreign designs from the early 1930s; the T-26 was based on the British Vickers 6-Ton , and the BT tanks were based on a design from American engineer J. Walter Christie . [12] In 1937, the Red Army had assigned engineer Mikhail Koshkin to lead a new team to design a replacement for the BT tanks at the Kharkov Komintern Locomotive Plant (KhPZ). The prototype tank, designated A-20, was specified with 20 mm (0.8 in) of armour , a 45 mm (1.77 in) gun, and the new Model V-2-34 engine, using less-flammable diesel fuel in a V12 conf...