The National Security Act of 1947: An Overview

Author: Notre Dame International Security Center

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For almost seventy-five years now, the National Security Act of 1947 has significantly impacted how Presidents develop and implement foreign policy, transforming not only America but the global community as well. It has changed the way the United States organizes its military and gathers information to establish better coordination and communication between the leadership and branches of government.  

What is the National Security Act of 1947 

On July 26, 1947, President Harry Truman signed the National Security Act with the goal of implementing a program that would provide security for the United States in the decades and even centuries to come. To achieve this end, the act made multiple organizational changes within the military and intelligence community.  

Following World War II, the Act reorganized the intelligence agencies and armed forces creating some of the most important institutions of America’s defense and international leadership. Some of them include the Central Intelligence Agency (CIA), the National Security Council (NSC), and the Joint Chiefs of Staff (JCS), and the Department of Defense (DOD):

  • National Security Council 

    • The National Security Act created the National Security Council to improve the coordination of the nation’s security assets and information gathering. The NSC's role is also to manage smaller subcommittees, addressing anything deemed a threat to US national security. The NSC is comprised of the President, Vice President, the President’s National Security Advisor, the Secretary of State, the Secretary of Defense, and other presidential appointees upon approval of the Senate.  

  • Central Intelligence Agency 

    • The National Security Act also established the Central Intelligence Agency (CIA) to coordinate the country’s intelligence operations. The CIA’s role is to advise the NSC on intelligence-related matters. They evaluate and advise their members about the intelligence activities of other government agencies. The leader of the CIA is a Senate-approved Director of Central Intelligence (DCI). The CIA has no police or law enforcement power and does not perform any internal security functions.  

  • Joint Chiefs of Staff 

    • The National Security Act established the Joint Chiefs of Staff to advise the President on military strategy and planning. Joint Chiefs of Staff includes the heads of the U.S. Army, Navy, Air Force, and Marine Corps. JCS has no power in leading combat forces and has no executive or command authority over the troops in their services.  

  • Department of Defense 

    • The National Security Act combined the former Department of War and the Navy Department into the Department of Defense. This reorganization was intended to ensure national security and better supervise U.S. military forces by creating a direct line of command for all military services. This change eliminates confusion and provides strategic and efficient administration of defense.  DOD is based in the Pentagon, and it includes the Joint Chiefs of Staff, providing actionable military strength and a foundation for U.S. national policy.  


By mandating a major reorganization of foreign policy and the military, The National Security Act created some of the most familiar and reliable institutions in U.S. security apparatus, making it one of the most important pieces of legislation in modern history.