The Potsdam Conference was held in Germany and was attended by "The Big Three": (all heads of government) Joseph Stalin, Winston Churchill, and Harry S. Truman. The goals of the conference: decide how to administer Germany (which had agreed to unconditional surrender), the establishment of postwar order, peace treaty issues, and countering the effects of the war.
The Iron Curtain Speech was a speech given by Winston Churchill to address the point that Eastern Europe was more or less controlled by the Soviet Union. His speech was about peace and happened in Missouri.
The Truman Doctrine was an American foreign policy which was stated by President Harry S. Truman. The purpose of the policy was to counter "Soviet geopolitical expansion" during the Cold War.