In 1931, the Soviet Union acquired from United States two Christie tanks with the intention of performing technical investigations to produce a tank which should equip the armored forces of the Red Army. The North American tank had a revolutionary characteristic: it could move on diverse terrains thanks to its tracks and, in this case, after having removed the tracks through a very simple operation, it could move faster on road thanks to its robust wheels fitted with a solid rubber ring which served as guide. This way it was born, in just a month, the BT tank (named after the words Bistrochodny Tank, or Fast Tank). The BT, even if it did not grant an exceptional performance, was undoubtedly a good tank. After its baptism of fire in Spain it fought in Manchuria against the Japanese, in Poland, in Finland and finally in Russian ground, where it operated actively until 1941 to be later used for reconnaissance and training until 1943. The BT tank was designed to serve with the long-range armored and mechanized units. It had as purpose to intervene in the enemy rearguard and take the neuralgic centers, such as headquarters, supply centers and airfields. In these circumstances its high speed was an indubitable advantage. The aforementioned possibility of this tank for moving on its wheels was never totally exploited by the Red Army in military operations. During its war career this vehicle underwent successive modifications and improvements. The BT-7 was born from a modification on its armor, which in this case was soldered and had inclined plates to decrease its vulnerability. From this model also a command version was produced, as well as another model to provide support from artillery fire, without having to modify the turret. During 1938 a new Diesel engine of twelve cylinders in V had been developed, specifically designed for being installed in tanks. Since then it was installed in all of the models of the BT-7 which were being produced. This way, the new engine provided to the armored divisions of the Red Army a much increased operational range in respect of what had been possible until that moment.