After Japan’s defeat in 1945, Korea was divided at the 38th parallel into a Soviet occupation zone in the north and the U.S. zone in the south. Relations deteriorated rapidly and war broke out in 1950 when North Korean forces invaded South Korea. The UN sent an international army under U.S. command to repel the Communist invaders. After three years of bitter fighting with heavy casualties on both sides an armistice was signed which permanently divided the peninsula