The conflict between Communist North Korea and Non-Communist South Korea. The United Nations (led by the United States) helped South Korea., 2.5 million persons lost their lives. In June 1950, North Korea, supplied and advised by the Soviet Union, invaded the South. The United Nations, with the United States as the principal participant, joined the war on the side of the South Koreans, and the People's Republic of China came to North Korea's aid. After more than a million combat casualties had been suffered on both sides, the fighting ended in July 1953 with Korea still divided into two hostile states. the US/UN was able to push the North back to the 38th parallel. Negotiations in 1954 produced no further agreement (stalemate), except they agreed to an armistice (stop fighting), and the front line has been accepted ever since as the de facto boundary between North and South Korea.