During the First World War the British and imperial armies conducted large-scale campaigns in Palestine and Mesopotamia that made enormous demands on Egypt and India. Meeting the logistical requirements of the campaigns was a formidable achievement that required the imposition of a closer and more authoritarian form of imperial control. This led to the deepening of imperial rule in Egypt and India and its introduction in the occupied territories in Palestine and Mesopotamia to regulate the mobilization and extraction of the vast amounts of man- and animal power, and food and fodder, which powered the armies to victory in 1917-18. Exposure to, and participation in, the First World War nevertheless caused great hardship and economic dislocation, and culminated in a nationalist backlash in 1919-20. The legacy of these events continues to reverberate as they contributed to the creation of the modern state of Iraq and the mandatory state of Palestine.