The aftermath of World War II saw the rise of two global superpowers, the United States and the Soviet Union. The aftermath of World War II was also defined by the rising threat of nuclear warfare, the creation and implementation of the United Nations as an intergovernmental organization, and the decolonization of Asia, Oceania, South America and Africa by European and East Asian powers, most notably by the United Kingdom, France, and Japan.
Once allies during World War II, the U.S. and the Soviet Union became competitors on the world stage and engaged in the Cold War, so called because it never resulted in overt, declared total war between the two powers. It was instead characterized by espionage, political subversion and proxy wars. Western Europe was rebuilt through the American Marshall Plan, whereas Central and Eastern Europe fell under the Soviet sphere of influence and eventually behind an "Iron Curtain". Europe was divided into a U.S.-led Western Bloc and a Soviet-led Eastern Bloc. Internationally, alliances with the two blocs gradually shifted, with some nations trying to stay out of the Cold War through the Non-Aligned Movement. The Cold War also saw a nuclear arms race between the two superpowers, and part of the reason that the Cold War never became a "hot" war was that the Soviet Union and the United States had nuclear deterrents against each other, leading to a mutually assured destruction standoff.
