Korean War

The Korean War began on 25 June 1950, when forces of the Democratic People's Republic of Korea (DPRK) crossed the 38th parallel and invaded the Republic of Korea (ROK). The peninsula had been divided after World War II, with Soviet and U.S. occupation zones hardening into rival states by 1948.

Within days the UN Security Council passed resolutions condemning the invasion and authorizing member states to assist South Korea. These votes were possible because the Soviet Union was boycotting the Council over the seating of the Republic of China rather than the People's Republic of China. Sixteen countries ultimately contributed combat forces to the United Nations Command, established under U.S. leadership with General Douglas MacArthur as its first commander.

The war moved in dramatic phases. North Korean forces pushed the ROK and U.S. troops into the Pusan Perimeter by August 1950. MacArthur's amphibious landing at Inchon in September 1950 reversed the front, and UN forces advanced deep into the north toward the Yalu River. In late October 1950, the People's Republic of China intervened with "Chinese People's Volunteers," driving UN forces back below Seoul. Soviet pilots flew MiG-15s covertly in support. By mid-1951 the front had stabilized roughly along the 38th parallel, and the conflict became a war of attrition.

Armistice talks opened in July 1951 and dragged on for two years over prisoner repatriation and the demarcation line. The Korean Armistice Agreement was signed on 27 July 1953 at Panmunjom by representatives of the UN Command, the Korean People's Army, and the Chinese People's Volunteers. South Korean President Syngman Rhee refused to sign. The agreement created the Demilitarized Zone (DMZ) but no peace treaty followed, leaving the two Koreas technically still at war.

Casualty estimates vary widely; millions of Korean civilians and soldiers, and hundreds of thousands of Chinese and UN personnel, were killed or wounded. The war entrenched Cold War alliances in East Asia and shaped the U.S.–ROK Mutual Defense Treaty signed later in 1953.