The Voluntary Aid Detachment (VAD) was a voluntary unit of civilians providing nursing care for military personnel in the United Kingdom and various other countries in the British Empire. The most important periods of operation for these units were during World War I and World War II. Although VADs were intimately bound up in the war effort, they were not military nurses, as they were not under the control of the military, unlike the Queen Alexandra's Royal Army Nursing Corps, the Princess Mary's Royal Air Force Nursing Service, and the Queen Alexandra's Royal Naval Nursing Service.