Marshal of the Royal Air Force Sir John Cotesworth Slessor, GCB, DSO, MC (3 June 1897 – 12 July 1979), sometimes known as Jack Slessor, was a senior commander in the Royal Air Force (RAF), serving as Chief of the Air Staff from 1950 to 1952. As a pilot in the Royal Flying Corps during the First World War, he saw action with No. 17 Squadron in the Middle East, earning the Military Cross, and with No. 5 Squadron on the Western Front, where he was awarded the Belgian Croix de Guerre. Between the wars he commanded No. 4 Squadron in England, and No. 3 (Indian) Wing, earning the Distinguished Service Order for operations with the latter in Waziristan. In 1936, he published Air Power and Armies, which examined the use of air power against targets on and behind the battlefield.