The United States did not prevent communism after World War II, but it did attempt to slow its spread. Two of the best examples of this are the Korean War and the Berlin Airlift.
In the Korean War, the United States assisted the fledgling South Korean government when the communist North Koreans invaded.
When the Soviet Union attempted to strangle Berlin, the United States flew nonstop missions to deliver much needed food, supplies and medicine (the Berlin Airlift).
Small proxy wars were fought all over the globe, most of which never directly involved the two 'superpowers.' This worldwide game of chess was repeated throughout the Cold War.
When the Soviets marched through eastern Europe they occupied it and therefore it was communist.
To contain the spread of communism in post-World War II Europe
The policy of the US toward the Soviet Union after WWII was shaped by a belief that the Soviets intended to spread Communism throughout the world.
George C. Marshall .
That Communism would spread all over the world.
Europe
The Marshall Plan sent United States monetary aid to Europe to help with reconstruction.
The Truman Doctrine promised support to any nation battling communism.
When the Soviets marched through eastern Europe they occupied it and therefore it was communist.
To contain the spread of communism in post-World War II Europe
The policy of the US toward the Soviet Union after WWII was shaped by a belief that the Soviets intended to spread Communism throughout the world.
At the end of World War II much of Europe was devastated so under the Marshall Plan the United States loaned $13 Billion to help rebuild Europe. One of the goals was to prevent the spread of communism.
George C. Marshall .
The spread of Communism.
That Communism would spread all over the world.
World War I had NOTHING to do with communism. Yea. It was during and after WWII. And the main country that fought to spread is was the Soviet Union, or Russia.
No one believed the rise of communism was a greater threat than Germany during WWII. Western Europe was allied with communist Russia during WWII, so they did not wish to destroy their ally. It wasn't until after WWII that fear shifted to the rise of communism, as communism spread all over Eastern Europe and even divided Germany.