the U.S. role in the cold war was to stop and contain the spread of communism to countries. President Truman created the Truman Doctrine stating that it would help defend countries being attacked by communist countries. In 1950 North Korea invaded South Korea and so the U.S. acted quickly to help protect south Korea but as the war continued North Korea had now been aided by China and Russia. After 3 years in Korea the war soon ended with no real decided winner. though this proved that the U.S. was determined to control communism and keep it from spreading to other countries.