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Phases

The first phase of the Cold War began shortly after the end of World War II in 1945. The United States and its Western European allies sought to strengthen their bonds and used the policy of containment against Soviet influence; they accomplished this most notably through the formation of NATO, which was essentially a defensive agreement in 1949. The Soviet Union countered with the Warsaw Pact in 1955, which had similar results with the Eastern Bloc. As by that time the Soviet Union already had an armed presence and political domination all over its eastern satellite states, the pact has been long considered superfluous. Although nominally a defensive alliance, the Warsaw Pact's primary function was to safeguard Soviet hegemony over its Eastern European satellites, with the pact's only direct military actions having been the invasions of its own member states to keep them from breaking away; in the 1960s, the pact evolved into a multilateral alliance, in which the non-Soviet Warsaw Pact members gained significant scope to pursue their own interests. In 1961, Soviet-allied East Germany constructed the Berlin Wall to prevent the citizens of East Berlin from fleeing to West Berlin, at the time part of United States-allied West Germany. Major crises of this phase included the Berlin Blockade of 1948–1949, the Chinese Communist Revolution of 1945–1949, the Korean War of 1950–1953, the Hungarian Revolution of 1956 and the Suez Crisis of that same year, the Berlin Crisis of 1961, the Cuban Missile Crisis of 1962, and the Vietnam War of 1964–1975. Both superpowers competed for influence in Latin America and the Middle East, and the decolonising states of Africa, Asia, and Oceania.

Following the Cuban Missile Crisis, the fourth phase of the Cold War saw the Sino-Soviet split. Between China and the Soviet Union's complicated relations within the Communist sphere, leading to the Sino-Soviet border conflict, while France, a Western Bloc state, began to demand greater autonomy of action. The Warsaw Pact invasion of Czechoslovakia occurred to suppress the Prague Spring of 1968, while the United States experienced internal turmoil from the civil rights movement and opposition to United States involvement in the Vietnam War. In the 1960s–1970s, an international peace movement took root among citizens around the world. Movements against nuclear weapons testing and for nuclear disarmament took place, with large anti-war protests. By the 1970s, both sides had started making allowances for peace and security, ushering in a period of détente that saw the Strategic Arms Limitation Talks and the 1972 visit by Richard Nixon to China that opened relations with China as a strategic counterweight to the Soviet Union. A number of self-proclaimed Marxist–Leninist governments were formed in the second half of the 1970s in developing countries, including Angola, Mozambique, Ethiopia, Cambodia, Afghanistan, and Nicaragua.

Détente collapsed at the end of the decade with the beginning of the Soviet–Afghan War in 1979. Beginning in the 1980s, the fifth phase of the Cold War was another period of elevated tension. The Reagan Doctrine led to increased diplomatic, military, and economic pressures on the Soviet Union, which at the time was undergoing the Era of Stagnation. The sixth phase of the Cold War saw the new Soviet leader Mikhail Gorbachev introducing the liberalizing reforms of glasnost ("openness") and perestroika ("reorganization") and ending Soviet involvement in Afghanistan in 1989. Pressures for national sovereignty grew stronger in Eastern Europe, and Gorbachev refused to further support the Communist governments militarily.

The fall of the Iron Curtain after the Pan-European Picnic and the Revolutions of 1989, which represented a peaceful revolutionary wave with the exception of the Romanian revolution and the Afghan Civil War (1989–1992), overthrew almost all of the Marxist–Leninist regimes of the Eastern Bloc. The Communist Party of the Soviet Union itself lost control in the country and was banned following the 1991 Soviet coup attempt that August. This in turn led to the formal dissolution of the Soviet Union in December 1991 and the collapse of Communist governments across much of Africa and Asia. The Russian Federation became the Soviet Union's successor state, while many of the other republics emerged from the Soviet Union's collapse as fully independent post-Soviet states. The United States was left as the world's sole superpower.

The Cold War has left a significant legacy. Its effects include references of the culture during the war, particularly with themes of espionage and the threat of nuclear warfare. The Cold War is generally followed by the categorization of international relations since 1989 and post–Cold War era to underline its impact.