The genesis of the Korean War occurred in 1945 when Korea was divided after the defeat of the Japanese in WW II. Known as the "Hermit Kingdom," Korea had been subjected to a long period of Japanese hegemony. A significant part of the postwar settlement provided for the partitioning of Korea into North and South with the 38th parallel as the dividing line. The Soviet Union would occupy the North and the United States would provide stewardship in the South. Kim Il Sung, a Communist, would rule the North and Dr. Syngman Rhee would head the government of the Republic of Korea in Seoul, in the South. The North, for five years, unsuccessfully attempted to subvert Dr. Rhee's government.
The frustration, by 1950, led to a military operation by the North, by moving troops south across the 38th parallel in June 1950. The North Korean People's Army surged across the border on 25 June 1950, routing South Korean forces and the American advisors. Seoul was overrun by 29 June by which time the Rhee government had been evacuated, American and global response was immediate and swift. The United Nations passed Security Council sanctions against the North. The Soviet Union's temporary absence from the council made this action possible. The North was directed to return its forces north of the 38th parallel. The North did not comply and on 30 June 1959, U.S. President Harry Truman ordered U.S. combat troops to Korea in support of ROK forces. And thus, the Korean War was joined. For more complete and detailed accounts of the Korean War, we suggest you explore the links below: