But at the Potsdam Conference in July, Truman knew that the U.S. had developed an atomic bomb that might help defeat Japan. The bomb was first tested at Alamogordo in New Mexico on July 16–the day before the Potsdam Conference began. The test had been a success.
When Truman told Stalin that the Americans had a powerful new weapon, the Soviet leader took the news calmly and wished Truman luck in using it against Japan. Through his network of spies in the United States, Stalin had already known about the bomb for some time.
The war in the Pacific was showing no signs of abating and the Western Allies were increasingly worried by the level of resistance they encountered. The Japanese had begun launching suicide kamikaze attacks on Allied ships, with the United States enduring the greatest losses. Almost five thousand Americans were killed and more than thirty ships destroyed off Okinawa in the spring of 1945.
In an attempt to avoid an invasion of the Japanese home islands, the Americans had mounted a massive bombing campaign, in which more than two hundred and fifty planes would attack a single target, dropping nearly two thousand tons of bombs at the firebombing of Tokyo in March 1945 had killed around one hundred thousand people. Despite this destruction, the Allies feared that a land invasion of Japan would still be necessary to end the war.
At the Imperial Palace in Tokyo, Japanese emperor Hirohito was unaware of the new American weapon, but he had been informed of the Potsdam Declaration . Hirohito and his government refused the document’s surrender terms. On August 6, the United States dropped an atomic bomb on Hiroshima, Japan.
In Moscow, news of the American nuclear attack motivated Stalin to enter the war against Japan, so on August 9, the Soviets launched Operation August Storm and attacked the Japanese in China. Three days later a second bomb was dropped on Nagasaki. Faced with annihilation, Japan surrendered on August 15. The Second World War was over.
As millions sang and danced in Allied cities around the world, Allied officials moved ahead with their postwar plans. At Nuremberg , the Allies held war crimes trials for captured Nazi leaders. In the first phase of the trials between November 1945 and October 1946, twenty-two Nazis were tried in front of an international military tribunal . Twelve were sentenced to death, three were acquitted, and the others received various prison sentences. In a series of subsequent proceedings, lasting until early 1949, almost two hundred Nazis were tried before U.S. military tribunals; twenty-four received death sentences, fifty-six were acquitted or released, and one hundred and seven went to prison.