The Battle of Chosin Reservoir, also known as the Chosin Reservoir Campaign or the Battle of Lake Jangjin, was an important battle in the Korean War. The name "Chosin" is derived from the Japanese pronunciation "Chōshin", instead of the Korean pronunciation.
The battle took place about a month after the People's Republic of China entered the conflict and sent the People's Volunteer Army 9th Army to infiltrate the northeastern part of North Korea. On 27 November 1950, the Chinese force surprised the US X Corps commanded by Major General Edward Almond at the Chosin Reservoir area. A brutal 17-day battle in freezing weather soon followed. Between 27 November and 13 December, 30,000 United Nations Command troops under the field command of Major General Oliver P. Smith were encircled and attacked by about 120,000 Chinese troops under the command of Song Shilun, who had been ordered by Mao Zedong to destroy the UN forces. The UN forces were nevertheless able to break out of the encirclement and to make a fighting withdrawal to the port of Hungnam, inflicting heavy casualties on the Chinese.