Battle of Chosin Reservoir

The Battle of Chosin Reservoir (17 November – 13 December 1950) was an important battle during the Korean War.
The United Nations Command, led by the United States, occupied North Korea, which had attacked South Korea.
The People's Republic of China entered the war after it had given several warnings to the United Nations. It attacked United Nations Command and forced its retreat.
In 1953, the Korean War ended with a stalemate. An armistice divided Korea at the 38th parallel.
Background.
North Korea invaded South Korea across the 38th parallel and occupied most of South Korea. The South Korean Army retreated to Busan.
The United Nations Command intervened, landed at Incheon, and captured Seoul. The United Nations occupied most of North Korea and approached its border with China, the Yalu River.
Chinese forces infiltrated into North Korea and hid there. Mao Zedong decided to attack the United Nations during the Second Phase Offensive.
Terrain.
The Korean Peninsula has a mountain range, the Taebaek Mountains, in its middle that divides the east from the west. The Chosin Reservoir was an artificial lake in hilly terrain in the northeast of the peninsula. A road connects the reservoir to the southeast to the port city of Hungnam.
Aftermath.
Despite their victory in the battle, the Chinese lost so many troops that they would not be able to win the war. Also, the United Nations learned lessons from the defeat and no longer had the effect of surprise.
Operation Glory occurred in 1954 to make permanent graveyards for those who had died during the battle.