In 1935, the BT-7 fast tank emerged, it was the maximum development of the BT tank series. It was armed with a 45mm gun similar to previous models, but the engine was replaced by the much more powerful aviation type M.17T Liberty. The first BT-7 version mounted the same turret as the previous BT-5, but from 1938 they mounted the T-26S tank turret and the armor was reinforced. When the USSR was attacked by Germany, the BT-7 was one of the most numerous tanks in the Red Army and even its gun was much superior to that of the German tanks, they suffered numerous losses when not were used with the appropriate tactics. Around 2,000 BT-7 were lost in the first year of fightings, reducing their number considerably. They ended the war fighting against the Japanese Army in Manchuria, in the operations of 1945.
BT-7 gallery and more info