Short answers, pulled from the story.
President Harry Truman signed the National Security Act of 1947 on the 26th of July 1947. He signed it aboard his VC-54C presidential aircraft, Sacred Cow, while flying to see his dying mother.
The act created the National Military Establishment, the National Security Council, and the Central Intelligence Agency. It also established the United States Air Force as an independent service and the position of secretary of defense.
Senator Chan Gurney sponsored the bill in the Senate, where it was introduced as S. 758 on the 3rd of March 1947. Representative Clare Hoffman introduced the companion bill, H.R. 2319, in the House on the 28th of February 1947.
The act followed years of debate over unifying the military after World War II exposed problems such as intelligence failures linked to Pearl Harbor and constant Army-Navy friction in the Pacific. President Truman proposed the legislation to Congress on the 26th of February 1947.
James Forrestal became the first secretary of defense after the Senate confirmed him, with most of the act's provisions taking effect the next day, on the 18th of September 1947. His powers were initially limited, and he struggled to make the office effective.
The 10th of August 1949 amendments converted the National Military Establishment into the Cabinet-level Department of Defense and placed the three military departments under the secretary of defense's authority. They also created a full-time chairman of the Joint Chiefs of Staff and renamed the War Council the Armed Forces Policy Council.