S. 758, National Security Act of 1947, July 10, 1947
Seeking to modernize and strengthen the nation’s defenses, Congress passed the National Security Act in July 1947. The act brought the Army, Navy, and Air Force together as the National Military Establishment (later renamed the Department of Defense) under the Secretary of Defense. It established the National Security Council and the Central Intelligence Agency under the executive branch.
Records of the U.S. Senate, National Archives and Records Administration
The Pearl Harbor Attack
On December 7, 1941, Japan attacked the United States Pacific Fleet at Pearl Harbor, Hawaii, killing thousands and destroying U.S. military ships and planes. Congress declared war against Japan the following day. At the end of the war, after seven military and presidential investigations had identified different reasons for the lack of U.S. preparedness at Pearl Harbor, Congress created a joint committee to review possible lapses in intelligence. Its findings led Congress to pass the National Security Act of 1947 to modernize national security agencies and coordinate military readiness.
The completely ineffective liaison between the Army and the Navy in Hawaii at a time when the fullest exchange of information was absolutely imperative dictates that military and naval intelligence, particularly, must be consolidated.
Pearl Harbor Committee, Investigation of the Pearl Harbor Attack, July 20, 1946