During the First World War, Great Britain invested a great deal in its medical services, and in most theatres of the war they were considered vital to military efficiency. It was at that point widely recognized that medicine improved manpower economy and morale. Medicine was also important in sustaining public support for war and civilians contributed to the medical welfare of soldiers either directly, as volunteers, or indirectly as donors. Medical themes figured prominently in propaganda, too, and in uniting Britain with its imperial territories. But the centrality of medicine to war in 1914–18 stands in marked contrast to previous campaigns. The recent war in South Africa revealed that medicine had been given little attention by military commanders, and that disease prevention and casualty disposal were poorly organized. This book examines the differences and similarities between medical arrangements in 1914–18 and earlier conflicts. It attempts to explain why medicine became central to military operations during the First World War and to account for variations in medical arrangements in different theatres of the war. The book also examines military medicine in all major theatres as well as neglected facets of wartime medicine such as work among civilians, imperial armies, and the imperial labour corps.