BT Fast TankWhen the Red Army needed to mechanise its cavalry branch in the 1930s, the BT fast tank was its solution. Based on the American Christie high speed tank, the Red Army began a programme to adapt the design to its own needs. Early versions were mechanically unreliable and poorly armed, but by the mid 1930s, the BT 5 emerged, armed with an excellent dual purpose 45mm gun. It saw its combat debut in the Spanish Civil War in 1937 and was later used in the