The Teheran Conference was most significant conference between the Big Three Allied leaders during World War II. It was held in Teheran, Iran (Persia) from 28 November to 1 December 1943. It brought together for the first time Franklin D. Roosevelt, British Prime Minister Winston Churchill and Soviet dictator Joseph Stalin. The main achievement was a growth in mutual trust between the Soviets and the Americans, with the British left out in the cold. At the conference the leaders agreed to concentrate their combined power in 1944 in a giant East-West pincer movement against Germany. To fulfill this pledge, the Americans and British promised to launch the invasion of northern France—Operation Overlord—in May, 1944. The Soviets promised a supporting attack on the Germans—Operation Bagration—from June through September. Roosevelt, with Stalin's help, put pressure on Churchill to support the cross-channel invasion, reducing the Mediterranean to a secondary theater. The Soviets also agreed to American requests to enter the war against Japan as soon as Germany was defeated. Stalin also agreed to vague plans Roosevelt had for a postwar United Nations. All the promises were kept. Conservatives have criticized Roosevelt for trusting Stalin too readily, and for not realizing Stalin's plans to rule Eastern Europe using the Red Army and the Communist party.
While Stalin was preoccupied with the opening of the second front in Europe, Roosevelt's priority was to pave the way for a postwar organization based on the Atlantic Charter and dominated by the 'Big Four' (the United States, Britain, China, and the USSR) to assure world peace and security. To reach Soviet agreement Roosevelt had to disabuse Stalin of his belief in an anti-Soviet collusion between the United States and Britain and to forge a direct US-Soviet working relationship. Churchill wanted to avoid a very high casualty invasion of France of the sort that had caused so many deaths in World War I, and wanted instead more action in the Mediterranean. The problem was that this would postpone the defeat of Germany.
Roosevelt clearly regarded the Soviet Union (not Britain) as the most important US ally and felt that he alone was capable of dealing with the Soviet leader. He also seemed prepared to grant most of Stalin's wishes and tended to override the opinions of his own staff and other allied leaders when they did not agree with Stalin's viewpoints. This bias in favor of the Soviet viewpoint is reflected in the results of the meetings at Teheran and Yalta, where the two leaders met and decided the postwar fate of Eastern Europe.
Eastern Europe boundaries
Secretly it was agreed to let Russia have not only eastern Poland but also part of Finland and parts of Romania. Roosevelt and Churchill agreed that the eastern borders of Poland would roughly follow the Curzon Line. The Polish government was not notified of this decision and the only information given was a press release claiming that "We await the day, when all nations of the world will live peacefully, free of tyranny, according to their national needs and conscience ". The result was Poland moved west, losing the Ukrainian provinces in the east and gaining formerly German provinces in the west.
Churchill agreed to support the Yugoslav Communist, Joseph Broz Tito, and desert the pro-Western, anti-totalitarian friend, General Mihailovich.
Upon Roosevelt's return to the United States, the President told a joint session of Congress that no secret arrangements had been made.
The soft underbelly
Churchill repeatedly sought more action in the Mediterranean, including an invasion in central Italy and an Allied invasion across the Adriatic from Italy to pierce the "soft underbelly." American and Soviet military strategists rejected the proposal as a diversion from the main attack on France.
Through the U.S. Office of War Information (OWI), Churchill's proposal of an Allied invasion across the Adriatic from Italy to pierce the "soft underbelly" of the Europe was ridiculed as "British Imperialism."
At the outset Stalin was concerned that vague Allied promises about a landing in France would never come about. The Conference reassured him that Overlord was real—and indeed it began on June 6, 1944 (slightly later than the promised May date). Stalin wanted the Allied forces in the Mediterranean to be used in an invasion of southern France, thus making victory in France over the Germans more likely.
General Mark Clark reported after the war that Stalin "throughout the Big Three Meeting and negotiations at Teheran was one of the strongest boosters of the invasion of southern France. He knew exactly what he wanted in a political as well as a military way; and the thing that he wanted most was to keep us out of the Balkans, which he had staked out for the Red Army.... I never could understand why, as conditions changed and as the war situation changed, the United States and Britain failed to sit down and take another look at the overall picture with a view to eliminating or reducing the scope of Anvil if something better was offered.... A campaign that might have changed the whole history of relations between the Western world and Soviet Russia was permitted to fade away." 
President Roosevelt's son, Elliot Roosevelt commented about the reaction to those present at the Teheran conference to Churchill's proposal:
"It was quite obvious to everyone in the room what he really meant. That he was above all else anxious to knife up into central Europe, in order to keep the Red Army out of Austria and Romania, even Hungary if possible. Stalin knew it, I knew it, everybody knew it...Trouble is, the P.M. is thinking too much of the postwar, and where England will be. He's scared of letting the Russians get too strong." 
Roosevelt told his son Elliott that "in between times Uncle Joe and I had a few words, too just the two of us." As Stalin's guest in the Russian embassy, Roosevelt was accessible for secret talks without Churchill's knowledge. One of these dealt with the Chinese Communist issue. Roosevelt told Elliott we couldn't do much about that "while Winnie was around."
Stalin raised his glass and said: "To the swiftest possible justice for all Germany's war criminals - justice before a firing squad. I drink to our unity in dispatching them as fast as we catch them, all of them, and there must be at least 50,000 of them."
Churchill flushed, leaped to his feet. He declared that any such mass murder was contrary to the British sense of justice. He was opposed to anybody, Nazi or anyone else, going before a firing squad without a proper legal trial.
Roosevelt said : "Clearly there must be some compromise ... Perhaps we could say that instead of summarily executing 50,000 we should settle on a smaller number, say 49,500." The Americans and Russians laughed. The British remained silent "in the presence of Churchill's mounting fury." Stalin called on everyone present for an opinion. Elliott said "Our armies will settle the matter for most of those 50,000 and perhaps a hundred thousand more." Stalin, greatly pleased, walked around the table to Elliott, put his arm around his shoulder and drank to his health. Churchill, infuriated, rushed to Elliott, shaking his finger in his face and crying: "Are you interested in damaging relations between the allies? Do you know what you are saying? How can you dare to say such a thing?" Elliott says he had a good reason to believe Churchill never forgot the incident but that his father, Franklin Roosevelt, was greatly amused by it.
Soon details about how the conference at Teheran captured the attention of the American public. All the little liberated countries to which Roosevelt had made such definite promises and whose people in this country had been so solicitously courted during the Presidential election of 1944 had been betrayed at Teheran. Roosevelt had scrapped the Atlantic Charter which asserted the "desire to see no territorial changes that do not accord with the freely expressed desires of the peoples concerned, that they respect the right of all peoples to choose the form of government under which they will live and they wish to see sovereign rights and self government restored to those who have been forcibly deprived of them." The Teheran agreement violated this pledge.
On December 20, 1944, the President at a press conference was asked what had become of the Atlantic Charter. Roosevelt replied there was not and never had been a complete Atlantic Charter signed by him and Churchill. Then where is the Charter now, he was asked. He replied: "There wasn't any copy of the Atlantic Charter so far as I know." The Charter had been on displa at the National Museum in Washington with the signatures of Roosevelt and Churchill. Daily visitors stood before it. The curator told journalists it came from the Office of War Information (OWI). OWI printed 240,000 copies of it. After press inquiries, the Charter was removed from the display at the National Museum.
Not long after Cordell Hull resigned as Secretary of State and Edward Stettinius named to succeed him.
- McNeill, William Hardy. America, Britain and Russia: their co-operation and conflict, 1941-1946 (1953), standard scholarly history
- Nisbet, Robert. "Roosevelt and Stalin". Modern Age 1986 30(2): 103-112, a conservative attack on FDR's eagerness to cooperate with Stalin online
- Sainsbury, Keith. The Turning Point: Roosevelt, Stalin, Churchill, and Chiang-Kai-Shek, 1943: The Moscow, Cairo, and Teheran Conferences (1986), standard scholarly history
- Mark Clark, Calculated Risk, Mark Clark, New York : Harper and Row, 1950, pp. 368-71.
- As He Saw It, Elliot Roosevelt, New York : Duell, Sloan, and Pearce, 1946, pp.. 184-85.
- Elliot Roosevelt, op.cit., p. 186-194, 202.
- The Roosevelt Myth, John T. Flynn, Fox and Wilkes, 1948, Book 3, Ch. 12, The Atlantic Charter Is Scrapped
- Materials of the Teheran conference, 28 November - 1 December 1943.