The country that tried to stop the spread of Communism would be the United States. After World War II, the United States saw the threat that Communism posed on the world, so they adopted policies to prevent the spread of it. These policies were known as containment because they were trying to contain the spread of Communism. This fueled the fire in what would be known as the Cold War, which was a time of heightened aggression between the United States and the Soviet Union. I hope this helps :)