Battle of the Chosin Reservoir, Chosin also called Changjin, campaign early in the Korean War, part of the Chinese Second Offensive (November-December 1950) to drive the United Nations out of North Korea. The Chosin Reservoir campaign was directed mainly against the 1st Marine Division of the U.S.X Corps, which had disembarked in eastern North Korea and moved inland in severe winter weather to a mountainous area near the reservoir. The campaign succeeded in forcing the entire X Corps to evacuate to South Korea, but the Chinese did not achieve their particular objective of isolating and destroying the 1st Marine Division. Instead, in a deliberate retrograde movement that has become one of the most-storied exploits in Marine Corps lore, the Marines turned and fought their way down a narrow vulnerable road through several mountain passes and a bridged chasm until they reached transport ships waiting at the coast.