The policy of containment was one of the most important policies the US developed. Not only did it suggest to actively seeking to prevent the spread of communism, but also it was also the key aim in "Truman Doctrine"--the Doctrine that veered the US's attitude towards the rest of the world. It said, "it was America's duty to interfere to 'help free peoples to work out their own destiny in their own way'", which abandoned the previous policy, the policy of isolation. How did the allies in the Second World War turn against each other and what caused the USA to abandon its long-term isolation policy?
In February 1945, the Big Three, Stalin, FDR and Churchill, met in Yalta. It was the second time the Big Three ever met. Even though the conference seemed to be successful, much tension had also been created. One of the points they agreed on was to help freed people of Europe set up democratic and self-governing countries by helping them to hold elections, but Stalin later on did not hold any elections in Eastern Europe, and the American press immediately turned hostile towards Russia.
This action of Stalin angered the people in Britain and America, thus they realized that Stalin should not be trusted completely. Tension usually was higher when countries mistrusted each other.
In July 1945, the Big Three met again in Potsdam, but two of the Big Three were new, President Truman of America and Prime Minister Attlee of Britain. They did not know what secret deals were agreed on in Yalta Conference, therefore they were a little passive, because Stalin could just make up some deals that were not agreed in Yalta, but they would never know. Stalin, in their eyes, was greedy because he kept asking for more...