The BT-7 was a Russian tank produced from 1935 which incorporated some design features from tanks developed by American engineer Walter Christie. “BT” stood for “Bystrokhodny Tank (Fast Tank)” as its coil spring Christie suspension system and powerful engine enabled an excellent on-road top speed of 50km/h. To further enhance speed and mobility, the tracks could be removed so that the tank could maneuver with its road wheels only. Equipped with a 47mm main gun, it was one of the better-armed tanks of that period and it also had sloped frontal armor, a feature that would make its way into later tanks such as the T-34. 4,700 BT-7s were produced from 1935 to 1939 and they were first deployed during the Spanish Civil War. They also took part in battles against Japanese forces in Mongolia and served on the Eastern Front until enough T-34s became available to replace them.