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.
Holt Manufacturing Company
As well as having a better power-to-weight ratio, a gasoline-engined tractor required fewer men to operate it. Competing steam engines typically required a crew of seven, including one highly skilled and well-paid, licensed "farm engineer". He was responsible for rising in the middle of the night to start the boiler fire to get up steam by first light. Steam traction boilers had a huge need for water and fuel, either coal or wood. Much of the seven-man crew's time was spent keeping it fueled.