The Second World War was a war of mobility, and within that nothing was more important than moving supplies to the armies, navies and air forces in the field. This movement of ammunition, food and new/replacement equipment is often described as logistics. The railway was the foundational means of supply for the great land war in Europe. No other transportation system was capable of efficiently hauling such enormous tonnages of supplies, or large numbers of men, over long distances. When compared to railways, trucks were less efficient, required considerably more manpower for the delivery of each ton of supplies, and needed greater support in terms of fuel and repair in order to fulfil their mission. Using air supply was usually a much more expensive option because of the relatively small amount of tonnage that could be carried by plane when compared to rail and road.