National Security Act of 1947

World War II exposed the costs of separate Army and Navy departments competing for resources and of intelligence scattered across agencies, failings blamed in part for Pearl Harbor. Harry Truman signed the National Security Act on July 26, 1947, aboard his plane before it left for Missouri to visit his dying mother. It took effect in September and remains the foundation of the national security bureaucracy.

The act created the National Security Council to advise the President, the Central Intelligence Agency under a Director of Central Intelligence, and the position of Secretary of Defense over a National Military Establishment. It separated the Air Force from the Army as a third military department and gave the Joint Chiefs of Staff a permanent statutory basis. Amendments in 1949 converted the National Military Establishment into the Department of Defense and strengthened the Secretary's authority over the services.

Later laws reshaped the structure the act created. The Goldwater-Nichols Act of 1986 strengthened the Chairman of the Joint Chiefs and the combatant commanders to force cooperation among the services. The Intelligence Reform and Terrorism Prevention Act of 2004 created the Director of National Intelligence above the CIA. Much of the modern presidency's foreign policy machinery, including the national security advisor and the NSC staff, grew from the 1947 framework.