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.

The Battle of Inchon was an amphibious invasion and battle of the Korean War that resulted in a decisive victory and strategic reversal in favor of the United Nations. The operation involved some 75,000 troops and 261 naval vessels, and led to the recapture of the South Korea capital Seoul two weeks later. The code name for the operation was Operation Chromite. The battle began on 15 September 1950 and ended on 19 September. Through a surprise amphibious assault far from the Pusan Perimeter that UN and South Korean forces were desperately defending, the largely undefended city of Incheon was secured after being bombed by UN forces. The battle ended a string of victories by the invading North Korean People's Army (NKPA). The subsequent UN recapture of Seoul partially severed NKPA's supply lines in South Korea. The majority of United Nations ground forces involved were U.S. Marines, commanded by General of the Army Douglas MacArthur of the United States Army. MacArthur was the driving force behind the operation, overcoming the strong misgivings of more cautious generals to a risky assault over extremely unfavorable terrain.