involved in that declaration since it was still neutral in the war against Japan. Japanese Prime Minister Kantarō Suzuki did not respond, which was interpreted as a sign that the Japanese had ignored the ultimatum. As a result, the United States dropped atomic bombs on Hiroshima on 6 August and on Nagasaki on 9 August 1945. The justifications used were that both cities were legitimate military targets and that it was necessary to end the war swiftly and preserve American lives. When Truman informed Stalin of the atomic bomb, he said that the United States "had a new weapon of unusual destructive force," but Stalin had full knowledge of the atomic bomb's development from Soviet spy networks inside the Manhattan Project and told Truman at the conference that he hoped Truman "would make good use of it against the Japanese." The Soviet Union converted several countries of Eastern Europe into satellite states within the Eastern Bloc, such as the People's Republic of Poland, the People's Republic of Bulgaria, the People's Republic of Hungary, the Czechoslovak Socialist Republic, the People's Republic of Romania, and the People's Republic of Albania. Many of those countries had seen failed Socialist revolutions prior to World War II. Regarding the establishment of the Oder-Neisse Line, President Truman reported that Stalin had presented the occupation of Eastern Poland by the Soviet Union and Polish annexation of Silesia and eastern Pomerania as a fait accompli. Taken by surprise, the Western Allies had been forced to abandon the principles of the Atlantic Charter. Previous major conferences Yalta Conference, 4 to 11 February 1945 Second Quebec Conference, 12 to 16 September 1944 Tehran Conference, 28 November to 1 December 1943 Cairo Conference, 22 to 26 November 1943 Casablanca Conference, 14 to 24 January 1943 See also Diplomatic history of World War II Foreign policy of the Harry S. Truman administration List of Soviet Union–United States summits Origins of the Cold War References Sources and further reading Beschloss, Michael. The Conquerors: Roosevelt, Truman, and the destruction of Hitler's Germany, 1941–1945 (Simon & Schuster, 2002) Cecil, Robert. "Potsdam and its Legends." International Affairs 46.3 (1970): 455-465. online Costigliola, Frank. Roosevelt's Lost Alliances: How Personal Politics Helped Start the Cold War (2013): 359–417. Davis, Lynn Etheridge. The Cold War Begins: Soviet-American Conflict Over East Europe (2015) pp 288–334. Farquharson, J. E. "Anglo-American Policy on German Reparations from Yalta to Potsdam." English Historical Review