BT-5

The BT-5 (Быстроходный танк-5) is the fifth variant of the BT light tank family. It is designed as a convertible tank, a feature invented by J. Walter Christie to reduce wear on the 1930s' unreliable tank tracks. The main advantage of this design is that the tank crew can quickly remove the tracks and connect a chain drive to the rearmost road wheel on each side, allowing the tank to travel at extremely high speeds on roads. The BT-5 variant, which featured a larger cylindrical turret housing a 45 mm 20-K tank gun and a coaxial 7.62 DT light machine gun, proved useful in the early stages of World War II. However, Soviet designers quickly discovered that the convertible option was of little practical use in a country with few paved roads; it took up space and added unnecessary complexity and weight. Later variants did not include the feature.