The Potsdam conference took place from 17 July to 2 August 1945 at the Cecilienhof, the homeland of Crown Prince Wilhelm in Potsdam. Participants were the Soviet Union, the United Kingdom and the United States. The leaders were represented by Communist Party General Secretary Joseph Stalin, Prime Minister Winston Churchill, then Clement Attlee and President Harry S. Truman. During the conference, Truman mentioned Stalin a “powerful new weapon” unspecified. Towards the end of the meeting, an ultimatum was issued in Japan to surrender or to deal with “rapid and total destruction,” which the new bomb did not mention. Prime Minister Kantaré Suzuki did not react. That is why, on August 6, 1945, the United States dropped atomic bombs on Hiroshima and on August 9, 1945 on Nagasaki. The justification was that both cities were legitimate military targets to quickly end the war and preserve American life.
However, some have suggested that Truman did not want Stalin to be involved in the conditions of Japan`s surrender. It should be noted that Truman postponed the Potsdam conference to ensure the functionality of this “powerful new weapon. When Truman informed Stalin of the atomic bomb, he did not explicitly mention its atomic character. However, Stalin had all his knowledge of the development of the atomic bomb due to Soviet spy networks as part of the Manhattan Project and told Truman at the conference that he had to “use this new addition to the Allied arsenal well. Eastern governments were informed of subsequent transfer methods and were asked to temporarily suspend deportations until reported by the Allied Control Board. The Big Three had been concerned about the Control Board reports, and they would look into it.  At the conference, Allied leaders reaffirmed their previous commitment to the revocation of the German population of Poland, Czechoslovakia and Hungary; governments in these countries had already implemented. Potsdam`s three allies were convinced that the transfer of this German population should be completed as soon as possible. They stressed that transfers should be carried out in an orderly and humane manner. In the long run up to two million German civilians were killed in forced displacement. [Citation required] Winston Churchill, who had served most of the war as British Prime Minister in a coalition government, was replaced by Clement Attlee during the conference. Since the early 1940s, Churchills had a Soviet policy that was very different from Roosevelt`s and regarded Stalin as an “evil tyrant” who led an abominable system.
 General elections were held in the United Kingdom on 5 July 1945, but the results were delayed to allow the counting of votes of military personnel in their constituencies. The result was known at the conference, when Attlee became the new Prime Minister. The leaders expressed their readiness to support any request for membership from states that remained neutral during the war and met other requirements.