When is the Air Force birthday? Published July 30, 2007 By John Williamson 100th Air Refueling Wing historian RAF MILDENHALL, England -- Like any birth, it was neither quick nor easy. For years, even before World War II, air-minded leaders strove to create an independent Air Force and during the postwar years, it finally became a reality. July 26, 1947, then-President Harry S. Truman approved and signed legislation known as the National Security Act of 1947, creating the National Military Establishment, to include the Departments of the Army, Navy, and Air Force. The new National Military Establishment came into being Sept. 17, 1947 when James V. Forrestal took the oath as the first Secretary of Defense. The following day, after two years of struggle for independence, the U.S. Air Force was established on Sept. 18, when the first Secretary of the Air Force, W. Stuart Symington, was sworn into office. As the former Assistant Secretary of War for Air, Symington was the right person for the job and instrumental in making the case for air power as a strategic deterrent to foreign aggression. Eight days later, on Sept. 26, Gen. Carl Spaatz became the first Chief of Staff of the Air Force. President Truman also signed a proclamation designating Aug. 1, 1946, as Air Force Day. For more information on this subject or on general Air Force History, visit: https://www.airforcehistory.hq.af.mil/publications.htm.