Victory in World War I relied on three types of energy: renewable energy for food and fodder, fossil energy, and high explosive. This column argues that the Allies had a clear advantage in manpower, coal, and agriculture, but not enough for a quick decision. Mobilisation in continental economies curtailed food production, occasionally to a critical level. Technical competition was a matter of capacity for innovation, not of particular breakthroughs. Coercive military service and rationing of scarce energy and food had egalitarian consequences that continued after the war.