During 1936–1940 Ismay was first the deputy secretary and then the secretary of the Committee of Imperial Defense. From 1940 to 1945 he was chief of staff to the Ministry of Defense and also deputy secretary (military) to the War Cabinet. In this position he worked closely with Prime Minister Winston Churchill and participated in many of the important wartime conferences, including Tehran, Yalta, and Potsdam. Ismay retired from the British Army as a general in 1946 and was created Baron Ismay of Wormington in 1947. He then served as chief of staff to the last viceroy of India, Earl Louis Mountbatten, and was secretary of state for Commonwealth Relations during 1951–1952.
Following the outbreak of the Korean War (1950–1953), the member states of NATO decided to strengthen that organization. Since a U.S. general was the organization's military head—its Supreme Allied Commander Europe (SACEUR)—the leaders decided to create the position of secretary-general, to be held by a European diplomat. Ismay was selected in March 1952 as the first secretary-general. He took up his position the next month and held it until May 1957. He was concurrently vice chairman of the North Atlantic Council (1952–1956) and its chairman (1952–1957).
As secretary-general, Ismay oversaw such matters as the establishment of basic alliance structures; the location of Supreme Headquarters Allied Powers Europe (SHAPE), outside of Paris; the expansion of the Western European Union; the admission of the Federal Republic of Germany (FRG, West Germany) to NATO membership; and the negotiations over the European Defense Community (EDC) and a Multinational Nuclear Force.
Ismay left his posts in May 1957 and was succeeded by Belgian Paul-Henri Spaak. Ismay retired to his farm in Gloucestershire and died at Wormington Grange, Broadway, Worcestershire, on 17 December 1965.
Spencer C. Tucker
Schmidt, Gustave, ed. A History of NATO: The First Fifty Years. 3 vols. New York: Palgrave Macmillan, 2001.