The Battle of Triangle Hill, also known as Operation Showdown or the Shangganling Campaign (Chinese: 上甘岭战役; pinyin: Shàng Gān Lǐng Zhàn Yì), was a protracted military engagement during the Korean War. The main combatants were two United Nations infantry divisions, with additional support from the United States Air Force, against elements of the 15th and 12th Corps of the People's Republic of China.