The First World War introduced the widespread use of lethal chemical weapons. In its aftermath, the British government, like that of many states, had to prepare civilians to confront such weapons in a future war. Over the course of the interwar period, it developed individual anti-gas protection as a cornerstone of civil defence. Susan R. Grayzel traces the fascinating history of one object – the civilian gas mask – through the years 1915–1945 and, in so doing, reveals the reach of modern, total war and the limits of the state trying to safeguard civilian life in an extensive empire. Drawing on records from Britain's Colonial, Foreign, War and Home Offices and other archives alongside newspapers, journals, personal accounts and cultural sources, she connects the histories of the First and Second World Wars, combatants and civilians, men and women, metropole and colony, illuminating how new technologies of warfare shaped culture, politics, and society.