Previously posted at: https://www.history.com/this-day-in-history/chinese-overwhelm-allies-in-north-korea
Three weeks after U.S. General Douglas MacArthur first reported Chinese communist troops in action in North Korea, U.S.-led U.N. troops begin a desperate retreat out of North Korea under heavy fire from the Chinese.
Near the end of World War II, the “Big Three” Allied powers–the United States, the Soviet Union, and Great Britain–agreed to divide Korea into two separate occupation zones and temporarily govern the nation. The country was split along the 38th parallel, with Soviet forces occupying the northern zone and Americans stationed in the south. By 1949, separate Korean governments had been established, and both the United States and the USSR withdrew the majority of their troops from the Korean Peninsula. The 38th parallel was heavily fortified on both sides, but the South Koreans were unprepared for the hordes of North Korean troops and Soviet-made tanks that suddenly rolled across the border on June 25, 1950.
Two days later, President Harry Truman announced that the United States would intervene in the Korean conflict to stem the spread of communism, and on June 28 the United Nations approved the use of force against communist North Korea. In the opening months of the war, the U.S.-led U.N. forces rapidly advanced against the North Koreans, but in October, Chinese communist troops entered the fray, throwing the Allies into retreat. By May 1951, the communists were pushed back to the 38th parallel, where the battle line remained for the rest of the war.
In 1953, an armistice was signed, ending the war and reestablishing the 1945 division of Korea that still exists today. Approximately 150,000 troops from South Korea, the United States, and participating U.N. nations were killed in the Korean War, and as many as one million South Korean civilians perished. An estimated 800,000 communist soldiers were killed, and more than 200,000 North Korean civilians died.
The original figure of American troops lost–54,246 killed–became controversial when the Pentagon acknowledged in 2000 that all U.S. troops killed around the world during the period of the Korean War were incorporated into that number. For example, any American soldier killed in a car accident anywhere in the world from June 1950 to July 1953 was considered a casualty of the Korean War. If these deaths are subtracted from the 54,246 total, leaving just the Americans who died (from whatever cause) in the Korean theater of operations, the total U.S. dead in the Korean War numbers 36,516.