The National Security Act of 1947

President Truman signs the National Security Act Amendment of 1949 in the Oval Office (Photo: Truman Libary)

The National Security Act of 1947, Pub. L. No. 235, 80 Cong., 61 Stat. 496 (July 26, 1947), signed by U.S. President Harry S. Truman realigned and reorganized the United States’ armed forces, foreign policy, and Intelligence Community apparatus in the aftermath of World War II. The majority of the provisions of the Act took effect on 18 September 1947, the day after the Senate confirmed James V. Forrestal as the first Secretary of Defense.

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 branches maintained quasi-cabinet status through their individual secretaries, but the act was amended on 10 August 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. The act created many of the institutions that Presidents found useful when formulating and implementing foreign policy, including the National Security Council (NSC). The Council itself included the President, Vice President, Secretary of State, Secretary of Defense, and other members (such as the Director of the Central Intelligence Agency), who met at the White House to discuss both long-term problems and more immediate national security crises.

The act also established the Central Intelligence Agency (CIA), which grew out of World War II era Office of Strategic Services and small post-war intelligence organizations. The CIA served as the primary civilian intelligence-gathering organization in the government. Later, the Defense Intelligence Agency became the main military intelligence body.

The act and its changes, along with the Truman Doctrine and the Marshall Plan, were major components of the Truman administration’s Cold War strategy.

Additional Reading:

• Michael H. Hogan, A Cross of Iron: Harry S Truman and the Origins of the National Security State, 1945-1954 (Cambridge, 1998).
• Melvyn A. Leffler, A Preponderance of Power; National Security, The Truman Administration, and the Cold War (Stanford, Connecticut, 1992).
• U.S. Department of State, Foreign Relations of the United States, 1945-1950, Emergence of the Intelligence Establishment (Washington, 1996)
• Text of the National Security Act of 1947 with Amendments (US Intel Community website)