The Cold War was a period of geopolitical tension between the United States and Soviet Union from 1945-1990. It involved ideological and strategic struggles over democracy vs communism and capitalism vs socialism. Though allies in WWII, the US and USSR had differing goals for postwar Europe that increased tensions. This led to an arms race, space race, and proxy wars as the two superpowers competed for global influence and tried to contain the spread of the other's ideology through policies like the Truman and Eisenhower Doctrines. Events like the Berlin Blockade, U-2 incident, and failed Bay of Pigs invasion heightened Cold War tensions.