Yalta, Potsdam, and the Postwar Order

Roosevelt, Churchill, and Stalin met at Yalta in February 1945, before Germany surrendered, with the Red Army already occupying most of Eastern Europe. They agreed Germany would be divided into four occupation zones, Stalin promised free elections in Poland and other liberated nations, and the Soviets agreed to enter the war against Japan. At Potsdam in July 1945, after Germany's surrender and with Truman now president and Stalin's armies still holding Eastern Europe, the Allies confirmed the zone divisions and split Berlin, deep inside the Soviet zone, into four sectors too. The agreements were made on the fly, under wartime pressure, and because Soviet troops already stood where they stood, Stalin had little reason to honor promises of free elections once the alliance cooled into rivalry. That military reality, not the paperwork, is what froze Eastern Europe behind what Churchill later called an iron curtain.

The United Nations, chartered in 1945, was built to fix exactly what had doomed the League of Nations after World War One: American absence and a requirement of unanimous consent that let any member block action. The UN's Security Council gave five major powers, including the United States and the Soviet Union, a permanent seat and a veto, trading pure fairness for a structure major powers would actually join and use.

Berlin became the flashpoint because it sat entirely inside Soviet-occupied East Germany yet was itself split four ways, forcing the Western Allies to supply their sectors by air during the 1948-49 blockade. Economically, the Bretton Woods agreements of 1944 pegged world currencies to the US dollar, which was itself pegged to gold, making the dollar the backbone of international trade and cementing American economic leadership alongside its new military and diplomatic weight.