In 1943, the leaders of Britain, the Soviet Union and the United States gather in Tehran, Iran, where they agree to work toward the defeat of Nazi Germany. They also begin to map out the future of post-war Europe.

The so-called "Big Three" meet again in February 1945 in Yalta, a town on the Black Sea and a resort for Russia's former czars.

While in Yalta, Joseph Stalin, now marshal of the Soviet Union, British Prime Minister Winston Churchill and U.S. President Franklin D. Roosevelt consider the fate of Poland, which is already occupied by the Soviets.

Yalta ends with Britain and the United States securing Stalin's agreement that the Soviets will attack Japan once Germany is defeated. Victory over the Nazis, meanwhile, is fast becoming reality. Soviet and U.S. troops meet on the Elbe River in April 1945, effectively cutting Germany in two.

Roosevelt dies soon after the Yalta summit, just weeks before V-E Day. Vice President Harry S. Truman then assumes the presidency and represents the United States at the first post-war "Big Three" meeting -- which takes place in Potsdam, just outside Berlin. But there are already signs that the wartime alliance between the West and the Soviets is quickly unraveling.
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