North Korea Invades South Korea

North Korea invades South Korea by crossing the 38th parallel, starting the Korean War. North Korea, led by Kim Il-Sung, is a Communist nation heavily supported by the Soviet Union, which occupied the northern portion of the Korean peninsula at the end of World War II. South Korea, led by the vehemently anticommunist President Syngman Rhee, is a partner of the United States, which controlled the southern half of the peninsula from 1945. 

Prior to the invasion, the Soviet Union provides the North Korean Army with modern military arms and vehicles as well as advisers, while the leader of Communist China, Mao Zedong, agrees to reinforce North Korea with Chinese troops, if necessary. By contrast, the South Koreans are not well equipped when compared with the North, and they lack sufficient numbers of antitank weapons, heavy artillery, ammunition reserves, and tanks.

The United Nations quickly condemns the invasion, but North Korea routs and nearly wipes out the South Korean armed forces within weeks. The invasion and the superiority of North Korean forces also catch the American military largely unprepared, as the United States is in the midst of downsizing its military forces after the end of World War II. By August, South Korean forces and the few U.S. troops remaining on the peninsula are pushed back to a small pocket, the “Pusan perimeter.”

To most leaders in the United States, the invasion is clear evidence that the Soviet Union is plotting a general takeover of Asia in addition to Europe, and it represents a crucial turning point in the evolving Cold War. President Harry S. Truman is determined to prevent the loss of non-Communist South Korea and extends his administration’s policy of “containment” to include Asia, committing U.S. military forces to the purpose. From this point on, most American policy and defense analysts view the political futures of Korea, Indochina, and the rest of Asia as inherently linked.1