Why did fuel make up such a large share of military supplies in World War II?

During World War II, fuel became a primary component of military supply due to the widespread mechanization of ground forces and the massive requirements of modern air power.

Historically, armies relied on forage to feed the draft animals used for transport. However, the 20th-century shift toward motor vehicles and aircraft fundamentally changed logistics. Unlike forage, which was often sourced locally, fuel had to be transported to the front in immense quantities to sustain mechanized operations. In the European theater, for example, fuel accounted for half of all resupply and replacement needs for U.S. forces.1

The transition to oil as a primary fuel source—favored for its higher energy density and ease of transfer compared to coal—further solidified its dominance in military logistics. While food remained a constant, essential requirement, it became a small fraction of the total supply burden compared to the vast amounts of fuel needed to maintain the mobility and striking power of modern, technologically advanced armed forces.21