The Korean War started on June 25, 1950, when North Korean troops invaded South Korea by crossing the 38th parallel. This marked the beginning of a three-year conflict that ended on July 27, 1953, with the signing of an armistice agreement that kept the two Koreas divided. The war involved major international players, with North Korea supported by China and the Soviet Union, and South Korea backed by United Nations forces led by the United States.