Final answer:
The War (Defense) Department's September 15, 1945 memorandum concerned demobilization after World War II and the reduction of the U.S. military, a move that was necessary but controversial among government officials.
Step-by-step explanation:
The War (Defense) Department's September 15, 1945 memorandum called for the reduction of the U.S. military and post-World War II demobilization. This was a point of tension as figures like Secretary of the Navy James Forrestal and Secretary of War Robert P. Patterson warned President Truman against a rapid demobilization, fearing it might jeopardize the nation's strategic position.
The United States eventually reduced its military size from a peak of 12 million individuals to 1.5 million by June 1947. Women, who had taken up positions in the workforce during the war, also faced dismissals as the war ended. Despite these reductions, the commitment to contain Soviet expansion necessitated a robust military defense, leading to the reorganization of the U.S. military under the National Security Act of 1947.
The National Security Act streamlined the nation's security efforts by creating entities like the National Security Council and the Central Intelligence Agency, and it paved the way for establishing the Department of Defense in 1949, consolidating the Department of War and other military departments. This reorganization reflected a shift towards maintaining a strong standing military in the face of Cold War tensions.