Which of the following unified the armed forces under a single agency, later known as the Department of Defense?

A) National Security Act of 1947
B) Marshall Plan
C) North Atlantic Treaty Organization
D) NSC-68

National Security Act of 1947

A major restructuring of the United States government's military and intelligence agencies following World War II, creating the Department of Defense, the Central Intelligence Agency (CIA), and the National Security Council (NSC).

Department of Defense

The Department of Defense is a federal agency responsible for coordinating and supervising all agencies and functions of the government relating directly to national security and the United States armed forces.

Armed Forces

The military forces of a country, including the army, navy, air force, and other branches responsible for defense and security.