The Cold War was a state of geopolitical tension after World War II between powers in the Eastern Bloc and powers in the Western Bloc. Historians do not fully agree on the dates, but a common timeframe is the period between 1947, the year the Truman Doctrine, a U.S. foreign policy pledging to aid nations threatened by Soviet expansionism, was announced, and either 1989, when communism fell in Eastern Europe, or 1991, when the Soviet Union collapsed. The term "cold" is used because there was no large-scale fighting directly between the two sides, but they each supported major regional wars known as proxy wars.
The Cold War split the temporary wartime alliance against Nazi Germany, leaving the Soviet Union and the United States as two superpowers with profound economic and political differences. The USSR was a Marxist–Leninist state led by its Communist Party, which in turn was dominated by a leader with different titles over time, and a small committee called the Politburo. The Party controlled the press, the military, the economy and many organizations.