The correct answer is "Cold War military alliances."
After World War II, the United States and Soviet Union emerged as global superpowers. Both of them were concerned with spreading their political, economic, and military power. In order to do this both countries made alliances. The United States helped to form the North Atlantic Treaty Organization (NATO) with countries like Great Britain, France, and Denmark. The Soviet Union went on to form the Warsaw Pact with countries like Romania and Albania.