Korean War

War from 1950 to 1953 between North Korea (supported by China) and South Korea, aided by the United Nations (the troops were mainly US). North Korean forces invaded South Korea on 25 June 1950, and the Security Council of the United Nations, owing to a walk-out by the USSR, voted to oppose them. The North Koreans held most of the South when US reinforcements arrived in September 1950 and forced their way through to the North Korean border with China. The Chinese retaliated, pushing them back to the original boundary by October 1950; truce negotiations began in 1951, although the war did not end until 1953. The Korean War established that the USA was prepared to intervene militarily to stop the spread of communism. After 1953 the Korean peninsula remained a Cold War battleground.

By September 1950, the North Koreans had overrun most of the South, with the United Nations (UN) forces holding a small area, the Pusan perimeter, in the southeast. The course of the war changed after the surprise landing of US troops later the same month at Inchon on South Korea's northwest coast. The troops, led by General Douglas MacArthur, fought their way through North Korea to the Chinese border in little over a month. On 25 October 1950, Chinese troops attacked across the Yalu River, driving the UN forces below the 38th parallel.

Truce talks began in July 1951, and the war ended two years later, with the restoration of the original boundary on the 38th parallel. The armistice was signed 27 July 1953 with North Korea, but South Korea did not participate, and a peace treaty did not follow.