The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc, that started in 1947, two years after the end of World War II, and lasted until the fall of the Soviet Union in 1991.

The term cold war is used because there was no large-scale fighting directly between the two superpowers, but they each supported opposing sides in major regional conflicts, known as proxy wars.

The Cold War was based on an ideological and geopolitical struggle for global influence by these two superpowers, following their roles as the Allies of World War II that led to victory against Nazi Germany and Imperial Japan in 1945. Aside from the nuclear arms race and conventional military deployment, the struggle for dominance was expressed indirectly, such as psychological warfare, propaganda campaigns, espionage, far-reaching embargoes, sports diplomacy, and technological competitions like the Space Race. The Cold War began with the announcement of the Truman Doctrine in 1947, started a gradual winding down with the Sino-Soviet split between the Soviets and the People’s Republic of China in 1961, and ended with the collapse of the Soviet Union in 1991.

The Western Bloc was led by the United States, as well as a number of First World nations that were generally capitalist and liberal democratic but tied to a network of often authoritarian Third World states, most of which were the European powers’ former colonies. The Eastern Bloc was led by the Soviet Union and its communist party, which had an influence across the Second World and was also tied to a network of authoritarian states. The Soviet Union had a command economy and installed similarly communist regimes in its satellite states. United States involvement in regime change during the Cold War included support for anti-communist and right-wing dictatorships, governments, and uprisings across the world, while Soviet involvement in regime change included the funding of left-wing parties, wars of independence, revolutions and dictatorships around the world. As nearly all the colonial states underwent decolonization and achieved independence in the period from 1945 to 1960, many became Third World battlefields in the Cold War.