who was winning the korean war before china entered the conflict
After the first two months of war, South Korean and U.S. forces rapidly dispatched to Korea were on the point of defeat, forced back to a small area in the south known as the Pusan Perimeter. In September 1950, an amphibious UN counter-offensive was launched at Incheon, and cut off many North Korean troops. Those who escaped envelopment and capture were forced back north. UN forces rapidly approached the Yalu River -- the border with China -- but in October 1950, mass Chinese forces crossed the Yalu and entered the war. The surprise Chinese intervention triggered a retreat of UN forces which continued until mid-1951.