During the Korean War, the Battle of Inchon turned the tide against the Korean People's Army (NKPA) for the Americans who were fighting under the United Nations Command. The U.S. Eighth Army, which made up most of the United Nations forces, then raced to the Chinese border but were defeated in the Battle of the Ch'ongch'on River after the entry of large numbers of Chinese troops on the North Korean side. United Nations forces were sent in retreat back down the Korean peninsula, and the retreat was the longest in U.S. military history.