Causes

1. The United States wanted to encourage free trade throughout the world. The Soviet Union wanted to shield off its own sphere from international commerce. Russia feared that trade with the West would involve the risk of Russia being opened to western influences which would have eroded the strength of the totalitarian regime. These differences led to much ill feeling between the United States and the Soviet Union.
2. The USSR installed pro-Soviet governments in areas that they captured from the Nazis during the war. The US and its allies sought to prevent further expansion of communist authority in Europe, leading to the proposal of the Marshall Plan.
3. There were strong differences over capitalism and communism. The United States sponsored capitalism while the Soviet Union sponsored communism and wanted to spread it throughout the world.
4. Nikita Khrushchev, successor of Joseph Stalin, developed a new type of communism that inspired generations of reformers in the Soviet Union and eastern Europe. This new style was without the terror and intimidation of previous styles of communism, and called for a more economically balanced type of communism.
5. The Americans made it clear that they would not let communism spread, which they made legally possible through the foreign policy of containment. This essentially meant that communism would be allowed to stay where it was, but it would not be allowed to propagate to other nations as an economic, social, or political system. The Soviets responded by doing their best to ensure that communism did indeed spread, so that the free-market capitalism of the West would not be allowed to spread. Obviously, this increased tensions between both groups.