Role of The United States
The U.S was involved in the Korean War by trying to stop the spread of communism further more, they had aided South Korea also, since they were nationalists and had called upon the Allies for help. They had especially helped by conjuring up naval forces(with General MacArthur) and had come to the Inchon Landing, where they forced North Korea to retreat when they had pushed South Korea too much further south. The retreat was a great achievement, because it had nearly disintegrated the North Korean army, but it also lead to the involvement of China, who had come to help aid the North Koreans.
The role of the United States was major, they had been the ones to drive back the North Korean army when they were at the brim of pushing South Korea too far, they came in and helped out, made them retreat far north and had helped South Korea stay nationalists and prevented their spread of communists.