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.
Light tanks of the United Kingdom
The biggest change from the Mark IV to the Mark V was the introduction of a three-man crew. The turret now carried the commander and the gunner who was also the radio operator. The increase in the crew size made a lot of difference to the tank's effectiveness and spread the maintenance load. Until then, the commander had to direct the driver, navigate, and operate the gun. If troop commander, he also had to direct the other tanks and their fire.