National Security Act
The National Security Act of 1947 realigned and reorganized the United States' armed forces, foreign policy, and Intelligence Community apparatus in the aftermath of World War II. The Act merged the Department of War and the Department of the Navy into the National Military Establishment (NME) headed by the Secretary of Defense. It was also responsible for the creation of a separate Department of the Air Force from the existing United States Army Air Forces. Initially, each of the three service secretaries maintained quasi-cabinet status, but the act was amended in 1949 to assure their subordination to the Secretary of Defense. At the same time, the NME was renamed as the Department of Defense. Aside from the military reorganization, the act established the National Security Council, a central place of coordination for national security policy in the Executive Branch, and the Central Intelligence Agency, the United States' first peacetime intelligence agency. (Public Law No. 235, 80 Cong., 61 Stat. 496).
Source: Terms & Definitions of Interest for DoD Counterintelligence Professionals, Office of the National Counterintelligence, https://www.dni.gov/files/NCSC/documents/ci/CI_Glossary.pdf