Walton Walker backed South Korea, and China allied with the Soviet Union in what was to become the first military action of the Cold War. Shortly after 75,000 North Korean troops with tanks invaded South Korea on June 25, 1950, American air and sea forces were ordered by President Harry S. Truman to give South Korean troops support. The U.S. Eighth Army was ordered to intervene and drive the invaders back across the 38th parallel, the border between the two countries. With only four lightly equipped and poorly trained divisions, Walker began landing troops on the southeast side of the Korean peninsula
North Korea–South Korea relations the South the following year, though the US Korean Military Advisory Group remained to train the Republic of Korea Army. As a result, two antagonistic states emerged, with diametrically opposed political, economic, and social systems. Both opposing governments considered themselves to be the government of the whole of Korea, and both saw the division as temporary. The DPRK proclaimed Seoul to be its official capital, a position not changed until 1972. North Korea invaded the South on June 25, 1950, and swiftly overran most of the country. In September 1950 the United Nations force, led by the United States, intervened