Korean War: Communist Chinese troops launch a massive counterattack (Battle of the Ch'ongch'on River and Battle of Chosin Reservoir) against United Nations and South Korean forces.

The Korean War was an armed conflict on the Korean Peninsula fought between North Korea and South Korea and their allies. North Korea was supported by China and the Soviet Union, while South Korea was supported by the United Nations Command (UNC) led by the United States. The conflict was one of the first major proxy wars of the Cold War. Fighting ended in 1953 with an armistice but no peace treaty, leading to the ongoing Korean conflict.

The Battle of the Ch'ongch'on River, also known as the Battle of the Ch'ongch'on, was a decisive battle in the Korean War that took place from November 25 to December 2, 1950, along the Ch'ongch'on River Valley in the northwestern part of North Korea. In response to the successful Chinese First Phase Campaign against the United Nations (UN) forces, General Douglas MacArthur launched the Home-by-Christmas Offensive to expel the Chinese forces from Korea and to end the war. Anticipating this reaction, the Chinese People's Volunteer Army (PVA) Commander Peng Dehuai planned a counteroffensive, dubbed the "Second Phase Campaign", against the advancing UN forces.

The Battle of Chosin Reservoir, also known as the Chosin Reservoir Campaign or the Battle of Lake Changjin, was an important battle in the Korean War. The name "Chosin" is derived from the Japanese pronunciation "Chōshin", instead of the Korean pronunciation.