Final answer:
The reorganization act of 1947 created the Department of Defense, which was responsible for overseeing the military services and coordinating national security efforts.
Step-by-step explanation:
The reorganization act of 1947, also known as the National Security Act of 1947, restructured the U.S. military and security apparatus. Its main function was to create the Department of Defense, which combined the Departments of the Army, Navy, and Air Force under one unified department. This department was responsible for overseeing the military services and coordinating national security efforts.