On January 14, 1943, the United States and Great Britain held the Casablanca Conference to discuss planning and strategy, particularly for the ongoing European theatre of World War II. U.S. President Franklin D. Roosevelt and British Prime Minister Winston Churchill led the delegations of their respective countries. Soviet leader Joseph Stalin declined to attend, stating that the ongoing Battle of Stalingrad required his presence in the Soviet Union. A delegation of the Free French forces also attended, led by Generals Charles de Gaulle and Henri Giraud. The conference produced the Casablanca Declaration, which contained the stipulation that the Allies would accept nothing short of the “unconditional surrender” of Germany and Japan.
(Taken from Wars of the 20th Century – World War II in Europe: Vol. 6)
“Big Three” Allied War Conferences The United States, Britain, and Soviet Union, the so-called “Big Three” Powers, met in two major war-time conferences, at Tehran (November 28 – December 1, 1944) and Yalta (February 4-11, 1945), and in the immediate post-war period, at Potsdam (July 17-August 2, 1945). At the Tehran (Iran) Conference, the Big Three agreed to align military strategy. At the Yalta Conference (Yalta, Crimea, USSR) which was attended by U.S. President Roosevelt, British Prime Minister Churchill, and Soviet leader Stalin, the Allies, now in an overwhelming military position, agreed on the disposition of post-war Germany and Europe. By then, Stalin was negotiating in a superior position, as his Red Army was only 40 miles (65 km) from Berlin. Stalin agreed to join the war in the Asia-Pacific against Japan, and become a member of the United Nations (both requested by the United States), but in return persuaded Roosevelt and Churchill to allow the following: that the Soviet-Polish border be moved to the Curzon Line, that the Soviets gain the South Sakhalin and Kuril Islands from Japan, that the Port Arthur lease be restored to the Soviets, and that Mongolia (a Soviet satellite polity since 1924) been detached from China.
Of major contention at Yalta was the issue of Poland, as Roosevelt and Churchill wanted to return the Polish government-in-exile (in London) to power, while Stalin insisted on installing the pro-Soviet government already operating in recaptured Polish territories In fact, Poland formed only part of the larger issue regarding the political future of Eastern Europe, where Stalin wanted to impose a Soviet sphere of influence to safeguard against another invasion from the West, while Roosevelt and Churchill wanted democratic governments to be established there. Instead, the Big Three signed the “Declaration of Liberated Europe”, where they agreed that European nations must be allowed “to create democratic institutions of their own choice” and to “the earliest possible establishment through free elections [of] governments responsive to the will of the people”. Free elections were to be conducted in Poland as well, and the Soviet-sponsored provisional government, while remaining predominant, would be encouraged to include non-communists “on a broad democratic basis”.
In the Potsdam agreement, the “Big Three”, now led by U.S. President Harry Truman (succeeding Roosevelt), British Prime Minister Clement Atlee (succeeding Churchill), and Stalin reaffirmed previous agreements with regards to dealing with post-war Germany and the territorial changes demanded by Stalin. As well, Germany was required to pay war reparations, and ethnic Germans were to be expelled from the former German lands and forced to move to within the new German borders. As Soviet domination of Poland was now a fait accompli, the Western Allies acquiesce to the authority of the pro-Soviet Polish government in that country.