The Battle of Chosin Reservoir, also known as the Chosin Reservoir Campaign or the Changjin Lake Campaign (Korean: 장진호 전투(長津湖戰鬪); Chinese: 长津湖战役; pinyin: Cháng Jīn Hú Zhànyì), was a decisive battle in the Korean War. "Chosin" is the Japanese pronunciation of the Korean name, "Changjin". Reportedly, updated maps in Korean were unavailable, hence the use of maps reflecting the Japanese pronunciation (Korea had been liberated from Japanese colonial rule only five years prior, in 1945).