Korean War (1950): Pusan Perimeter

Japanese colonial rule ended in August 1945. US troops occupied south of the 38th parallel, Soviet troops the north. Separate elections and the 1948 founding of the ROK and DPRK made partition political, not only military. Border raids and the 1948-49 guerrilla war on Jeju and in the southern mountains were already killing Koreans before the conventional invasion of June 1950. Kim Il-sung obtained Stalin's and Mao's assent after months of lobbying.

ROK and the first US task forces were driven into a corner at Pusan by August. MacArthur's Inchon landing (Operation Chromite, 15 September) cut the KPA's supply and enabled the recapture of Seoul on 28 September. UN forces then crossed the 38th parallel and drove toward the Yalu. Chinese intervention from mid-October, formalised as the People's Volunteer Army under Peng Dehuai, reversed the war again in the winter of 1950-51.

Ridgway restabilised the Eighth Army in early 1951. After Seoul's last recapture, the front settled near the parallel. Talks that began at Kaesong in July 1951 moved to Panmunjom and dragged for two years, hung up on POWs and the line of demarcation. US air power destroyed northern cities and infrastructure; MiG Alley saw the first large jet-versus-jet war. Neither bombing nor ground offensives (Heartbreak Ridge, Pork Chop Hill) broke the political deadlock.