Before the Korean War, the United states had spent much of their efforts on slowing communism and dealing with the Cold War. The Containment Policy was put in place, calling for the U.S. to resist any attempts to form communist governments elsewhere in the world. As America had become very wary of communism, President Truman took a step to fight communism by establishing the Truman Doctrine in 1947. The Marshall plan was approved by congress in 1948. Both of these acts were put in place to aid poor European countries in hopes that they would not need turn to communism to meet their needs.
When the time came and Communist North Korea invaded Non-Communist South Korea, the United States felt the need to fight beside South Korea.
When the time came and Communist North Korea invaded Non-Communist South Korea, the United States felt the need to fight beside South Korea.