The Korean War began in 1950 when North Korea invaded South Korea, pushing UN forces back to the Pusan perimeter. The UN authorized US troops to defend South Korea and appointed General Douglas MacArthur. MacArthur launched an amphibious invasion at Inchon, surprising North Korean forces and pushing them back above the 38th parallel. However, Chinese forces intervened on behalf of North Korea and pushed UN forces back south. This led to a stalemate along the 38th parallel from 1951-1953, with heavy casualties on both sides, before an armistice was signed, dividing Korea along the original border.