The end of WWII had left the United States and the Soviet Union as the two global superpowers, and Korea, a Japanese protectorate, was far down their respective lists of priorities, so the 38th Parallel was selected as the dividing line between the Russian and American occupation forces. The active support of the American occupation forces ensured that American-educated Syngman Rhee was elected president of the Republic of Korea (ROK). Kim Sung-il, who had served with the Red Army during WWII, became the Soviets’ candidate in North Korea. Aware that Rhee would provoke a war if permitted, the United States had refused to provide the ROK army with planes, tanks and artillery. However, Stalin approved Kim’s invasion plan, supplying the North Koreans with generous quantities of planes, tanks and artillery.
When the North Korean People’s Army (NKPA) crossed the border on June 25, 1950, its large, well-trained army steamrolled through the unprepared ROK forces. President Harry Truman won the support of the United Nations for the defense of South Korea, assigning the military response to General Douglas MacArthur, commander of the American occupation forces in Japan, but the NKPA had gained control of all of Korea by August except for a small perimeter around the port of Pusan. The NKPA had already burned itself out with repeated frontal attacks when an amphibious landing at Inchon caught the North Koreans completely by surprise. Seoul was recaptured on September 25, and the NKPA began to disintegrate.
Deciding to reunify Korea by force, an overconfident MacArthur dismissed China’s warning that it would not permit American troops near the Yalu River, the border between China and North Korea. The entry of hundreds of thousands of Chinese ‘volunteers’ into Korea in late November transformed the war. After a series of Chinese offensives and American counter-offensives, the lines had stabilized near the 38th Parallel by mid-summer 1951. The negotiations dragged on until mid-1953 because the Chinese and NKPA would not accept the right of Chinese and North Korean PoWs in UN custody to refuse repatriation to their home countries.