The Allied Powers during World War II (1939–1945) were Great Britain, the Soviet Union, and the United States. Those three nations held a number of conferences during the conflict to coordinate their strategy against the Axis Powers (Germany, Italy, and Japan). By May 1945, the war in Europe was over. Therefore, Potsdam—which took place from July 17, to August 2, 1945—was the last of these meetings.
The main reason why Potsdam was the beginning of the Cold War was Germany's complete defeat. The Anglo-American alliance with Soviet Russia was an unnatural one: only a common hatred of Nazi Germany had kept them together. There had been a lot of hostility and distrust between Moscow and the West before the war, and they resurfaced after Germany's surrender. In addition, the West feared the Soviet troops might Communize the lands they occupied.
Stalin, leader of the Soviet Union, had attended all of the previous meetings of the Big Three and he was present at Potsdam. Winston Churchill, British prime minister, was also experienced at these conferences. Stalin and Churchill did not trust each other. Churchill was especially suspicious of Stalin's motives and machinations in Eastern Europe, and talks over the fate of Poland were fraught. Potsdam was the first conference for America's new president, Harry S. Truman.
The leaders of the three nations discussed the occupation and administration of Germany and Austria, the establishment of Polish borders, reparations, and the unfinished war against Japan. The Potsdam Declaration, which demanded Japanese surrender, was issued.
The Potsdam Agreement, which ended the conference, was open to diverse interpretations. It broke down within a couple of years.