The central focus of U.S. foreign policy during the Cold War era was the containment of communism. This strategy aimed to prevent the spread of communism, particularly as promoted by the Soviet Union. Various tactics, including military alliances like NATO, economic aid such as the Marshall Plan, and active participation in conflicts (e.g., Vietnam War), were employed to support this policy. The Cold War was characterized by ideological competition, nuclear arms race, and proxy wars, fundamentally shaping international relations throughout the 20th century.