Answer:
The United States and the Soviet Union maintained an alliance during the war, but once the war was over, Stalin broke promises made at the Postdam Conference. Relations between the two nations degenerated as the Soviets installed puppet governments in Eastern Europe, which the former prime minister of Great Britain called an Iron Curtain dividing Europe, leading President Harry Truman to distrust Soviet leaders.
Step-by-step explanation:
The beginning of the Cold War was marked by the degenration of relationships between the USSR and the Western Allies. At the end, war exhaustion made the US to see the USSR as a power to be contained more than to be eliminated,This was the mantra of the Truman Administration, that would eventually lead to the victory of Eisenhower in the 1953 elections, that were marked by Machartysm and the rollback message, that is the US would try to conuter the Soviet influence (it need to be remembered that in 1949 China became a communist country)