The Department of the Air Force is responsible for defending the United States through control and exploitation of air and space. The Department of the Air Force (USAF) was established as part of the National Military Establishment by the National Security Act of 1947 (61 Stat. 502) and came into being on September 18, 1947. The National Security Act Amendments of 1949 redesignated the National Military Establishment as the Department of Defense, established it as an executive department, and made the Department of the Air Force a military department within the Department of Defense (63 Stat. 578). The Department of the Air Force is separately organized under the Secretary of the Air Force. It operates under the authority, direction, and control of the Secretary of Defense (10 U. S. C. 8010). The Department consists of the Office of the Secretary of the Air Force, the Air Staff, and field organizations.