Tensions arose between the United States and the Soviet Union because both emerged as the dominant superpowers in the aftermath of WWII. Moreover, the ideologies of these countries differed. The United States favored a capitalist system and the Soviet Union supported Communism. The partition of Germany into East and West Germany and the fear that Communism would spread to other parts of the world led to efforts to contain the threat. Competition between the two countries also led to the Space Race.