The new National Military Establishment, including the Office of Secretary of Defense and the Departments of the Army, Navy and Air Force, came into being on September 17, 1947. President Harry S. Truman had approved the National Security Act of 1947 on July 26. He also issued Executive Order 9877 which by presidential directive outlined the duties of the three services. Each was responsible for the area in which it operated -- ground, sea and air, although the Navy retained an air arm and the Marine Corps. The very next day, W. Stuart Symington was sworn in as the first secretary of the Air Force with the new Secretary of Defense James V. Forrestal in attendance. After many years of planning, an independent air arm was formed, an equal to the Army and Navy. Based on achievements in air superiority, the Air Force became the "first line of defense" in a post-war world. Shortly after taking office, Symington said: "In this day when a powerful counterattack is America's only real answer to aggression, there can be no question that we need the world's first Air Force. It is only through the global, flashing mobility of the Air Force that we can hold our counterattack poised ... we feel, with deep conviction, that the destiny of the United States rests on the continued development of our Air Force."