The Battle of Kumsong (Chinese: 金城战役) was one of the last battles of the Korean War.
During ceasefire negotiations, the United Nations, Chinese and North Korean forces were unable to agree on the issue of prisoner repatriation.
Refusing to sign the armistice, South Korean President Syngman Rhee released 27,000 North Korean prisoners who had refused repatriation to the North.
Outraged by the POW release, Chinese and North Korean commands launched the last large-scale offensive of the war at the Kumsong salient. (Salient = a piece of land or section of fortification that juts out to form an angle).
Nine ROK and U.S. divisions were required to block and counterattack the Chinese advance.
Penetrating approximately 6 miles south, the Chinese proclaimed victory as their last counteroffensive flattened out the salient.
Main source: Battle of Kumsong – Wikipedia