N. Korea convinced Stalin to supply them with weapons and support. S. Korea requested the same from the USA, but Truman declined, still wary from WWII. N. Korea (supported by USSR and China) attacks just after all US troops had left Korea. They invade South Korea (supported by USA), UN demanded N. Korea withdrawal, when refused, MacArthur appointed supreme commander of UN forces. Task Force Smith was deployed at the front line, coming from the 24th Infantry Division occupying Japan. These troops were not very well trained, and outnumbered. S. Korean and UN forces were pushed back to Pusan Perimeter, N. Korea takes Seoul. MacArthur (against the odds) succeeds in Inchon Invasion (where it was only deep enough in September to accommodate US ships. UN and S. Vietnamese forces push to the Chinese border (Yalu River), ignoring Chinese warning (MacArthur wanted to nuke China). Chinese Volunteer Army (with around 3 million units) push back to the original 38th parallel. Stalemate occurs, and truce is called.