A war, also called the Korean conflict, fought in the early 1950s between the United Nations, supported by the United States, and the communist Democratic People's Republic of Korea (North Korea). The war began in 1950, when North Korea invaded South Korea. The United Nations declared North Korea the aggressor and sent military aid to the South Korean army. President Harry S. Truman declared the war a “police action” because he never asked Congress to pass an official declaration of war. He thereby established a precedent for President Lyndon Johnson, who committed troops to the Vietnam War without ever seeking a congressional mandate for his action.
General Douglas MacArthur commanded the United Nations troops, who were mostly from the United States. The tide turned against North Korea with the landings at Inchon, and its troops were pushed back into the north; but reinforcements from the People's Republic of China soon allowed the North Koreans to regain lost territory. In 1953, with neither side having a prospect of victory, a truce was signed. In the course of the war, President Truman removed MacArthur from his command for insubordination. (See Truman-MacArthur controversy.)