How and why did the unites states policy toward the soviet union change soon after world war ii?

The United States and the Soviet Union cooperated with one another as allies during World War II, sharing a focus especially on defeating Germany.  But their alliance was based on a common enemy, not on a common ideology.  After the war, the United States viewed the Soviet Union with much suspicion.  The two nations distrusted each other and were often at odds -- beginning with incidents like the Berlin Blockade and Berlin Airlift, and continuing throughout what would become known as the Cold War.