The "Big Three" leaders at Yalta: from left to right, Churchill, FDR, and Stalin.

In February 1945, the leaders of the "Big Three" Allies--the United States, Great Britain, and the Soviet Union--met at Yalta on the northern shore of the Black Sea in the Soviet Union. World War II was almost over. Allied forces were in Europe at last: The Soviets were fighting their way west toward Nazi Germany, and the Americans and British were fighting their way east toward the same goal. Allied victory in Europe seemed inevitable although no one could tell how long it would take to conquer Germany. The three leaders were U.S. President Franklin D. Roosevelt, known as FDR; British Prime Minister Winston Churchill; and Soviet Premier Joseph Stalin.

The stated goal of the Yalta Conference was to decide on a plan for organizing Europe after the war, reestablishing sovereignty for nations overrun by the Nazis, and establishing democracy throughout Europe. ("Sovereignty" means a nation is independent--no other nation is controlling it.) But FDR and Churchill soon found that Stalin had no intention of doing the last two things. Stalin's plan for organizing Europe after the war involved occupying the eastern half of the continent and forcing it into the Soviet Union. FDR left the Yalta Conference gravely concerned about how he and Churchill would manage Stalin, but he agreed with Churchill that once the Allies had won the war, Stalin could be forced to go along with the plans for democracy.

Just five months later, in July 1945, the Big Three met again, this time in the city of Potsdam, Germany. Things were very different at the Potsdam Conference: the Allies had won the war, but it wasn't FDR and Churchill who dealt with Stalin. FDR had died in April, and the U.S. was represented by President Harry Truman. Churchill was voted out of office during the conference and replaced by a new prime minister, Clement Attlee. Only Stalin remained, and his plans for European domination were unchanged. The optimism of Yalta was replaced by the realization that a new war was beginning on the heels of the old one: a war for control of Europe and the world between the Soviet Union and the United States.