Tanks in World War I
The continued need for four men to drive the tank was solved with the Mark V which used Wilson's epicyclic gearing in 1918. Also in 1918 the French produced the Renault FT, the result of a co-operation between Estienne and Louis Renault. As mentioned before, it had the innovative turret position, and was operated by two men. At just 8 tons it was half the weight of the Medium A "Whippet" but the version with the cannon had more firepower. It was conceived for mass production, and the FT became the most produced tank of World War I by a wide margin, with over 3,000 delivered to the French Army. Large numbers were used by the Americans and several were also lent to the British.
Tanks in World War II
The Soviet Union began and ended the war with more tanks than the rest of the world combined (18,000–22,000). At the start of World War II the most common tank in Soviet service was the T-26 (derived from the Vickers 6-ton), lightly armoured and armed with a 45 mm gun capable of penetrating most German tanks at normal combat ranges. Few had radios. The design was mechanically sound although incapable of further development. The BT tank series, based on the Christie suspension system, were usually armed with the same 45 mm gun and were the most mobile tanks in the world. Close-support versions of both tanks existed, armed with 76.2 mm howitzers. However, the BT was at the end of its design life. The Red Army also fielded thousands of light reconnaissance tanks such as the amphibious T-37 and T-38 tanks. These had limited combat value; although highly mobile, they were armed only with 7.62 mm machine guns and had very thin armour. The Red Army also had about 400 T-28 medium, multi-turreted tanks, which were in most respects equal to the German Panzer IV. Again, though, this design dated from 1931 and was obsolete.