On August 15th, 1945, Allied forces divided the Korean Peninsula along the 38th parallel in order to create a line above which Russia would take responsibility for Japanese surrender, and below which the United States would do the same. The line shortly became a political boundary, and the Soviets treated North Korea as its own, supplying state-of-the-art weaponry and Communist propaganda.
On June 25th, 1950, North Korea invaded South Korea, breaking through the sparse forces of the ROK Army, and headed towards Seoul. The United Nations asked its members for assistance in an emergency session. President Truman offered air, logistical, and naval support, but it was soon made apparent that outside ground forces would be required. The Eighth U.S. Army was moved piece by piece to the area, and its first measure, "Task Force Smith", fought a valiant yet futile battle against the North Koreans' Soviet-built tanks. The 25th and 24th Infantry Regiments were the next into the war, working to slow the North Korean advance. The 24th lost at Taejon in a slow, bloody fight. North Korea continued its movement south, and the 25th Infantry and the 1st Cavalry Divisions bolstered the front lines, which eventually were pushed to the southeast corner of South Korea, in the vicinity of Pusan. General Walton H. Walker, commander of the EUSA at the time, stated that "The Eighth Army would stay in Korea until the invader was expelled from the territory of the Republic of Korea."