Food was the most important resource during the First World War. Without it, the massive armies on the Eastern and the Western Fronts, in Africa and in Asia could not have been assembled, let alone made to fight. And at the 'home front', which during the First World War came to be seen as integral to the war effort, food was crucial in maintaining production and morale. Any analysis of why and how the First World War was fought and won is incomplete without a consideration of how states, armies, communities, and individuals fought over the globe's supplies of grains, livestock, fertilizers, feeding stocks, and agricultural labour. This chapter will provide an analysis of the impact of this first global war on the worldwide food distribution system that had evolved since the Industrial Revolution. Its aim is to provide both an introduction to the reader on the impact of the First World War on food, and vice versa, and to provide essential contexts for both the chapters that follow and the data on changes in food supply and consumption, and its manifold effects on state, social structures, and health.