On August 14, 1945, Japan surrendered and World War II was over. American policymakers have argued that the atomic bombs were the precipitating cause of the surrender. Historical studies of the Japanese decision, however, reveal that what the Japanese were most concerned with was the Soviet Union's entry into the war. Japan surrendered with the understanding that the emperor system would be retained. The United States agreed to do what President Truman had been advised to do before the bombings: it signaled to the Japanese that they would be allowed to retain the emperor. This has left historians to speculate that the war could have ended without either the use of the two atomic weapons on Japanese cities or an Allied invasion of Japan.
The US Strategic Bombing Survey concluded that, even without the use of the atomic bombs, without the Soviet Union entering the war and without an Allied invasion of Japan, the war would have ended before December 31, 1945, and, in all likelihood, before November 1, 1945. Prior to the use of the atomic bombs on Hiroshima and Nagasaki, the United States was destroying Japanese cities at will with conventional bombs. The Japanese were offering virtually no resistance. The United States dropped atomic bombs on a nation that had been largely defeated and was trying to surrender at the time of the bombings.
Despite strong evidence that the atomic bombings were not responsible for ending the war with Japan, most Americans, particularly those who lived through World War II, believe that they were. Many World War II-era servicemen who were in the Pacific or anticipated being shipped there believed that the bombs saved them from fighting hard battles on the shores of Japan, as had been fought on the islands of Iwo Jima and Okinawa. What they did not take into account was that the Japanese were trying to surrender, that the United States had broken the Japanese codes and knew they were trying to surrender, and that, had the United States accepted their offer, the war could have ended without the use of the atomic bombs.
Most high-ranking Allied military leaders were appalled by the use of the atomic bombs. General Eisenhower, the Supreme Commander of Allied Forces Europe, recognized that Japan was ready to surrender and said, "It wasn't necessary to hit them with that awful thing." Gen. Hap Arnold, commander of the US Army Air Corps, pointed out, "Atomic bomb or no atomic bomb, the Japanese were already on the verge of collapse."
Adm. William Leahy, Truman's chief of staff, put it this way: "The use of this barbarous weapon at Hiroshima and Nagasaki was of no material assistance in our war against Japan. The Japanese were already defeated and ready to surrender. In being the first to use it, we adopted an ethical standard common to barbarians of the Dark Ages. Wars cannot be won by destroying women and children."
What Truman had described as "the greatest thing in history" was actually, according to his own military leaders, an act of unparalleled cowardice, the mass annihilation of men, women and children. The use of the atomic bombs was the culmination of an air war fought against civilians in Germany and Japan, an air war that showed increasing contempt for the lives of civilians and for the laws of war.
The end of the war was a great relief to those who had fought for so long. There were nuclear scientists, though, who now regretted what they had created and how their creations had been used. One of these was Leo Szilard, the Hungarian émigré physicist who had warned Einstein of the possibility of the Germans creating an atomic weapon first and of the need for the United States to begin a bomb project. Szilard had convinced Einstein to send a letter of warning to Roosevelt, which led at first to a small project to explore the potential of uranium to sustain a chain reaction and then to the Manhattan Project, which resulted in the creation of the first atomic weapons.
Szilard did his utmost to prevent the bomb from being used against Japanese civilians. He wanted to meet with President Franklin Roosevelt, but Roosevelt died on April 12, 1945. He next tried to meet with the new president, Truman, but Truman sent him to Spartanburg, South Carolina, to talk with his mentor in the Senate, Jimmy Byrnes, who was dismissive of Szilard. Szilard then tried to organize the scientists in the Manhattan Project to appeal for a demonstration of the bomb rather than immediately using it on a Japanese city. The appeal was stalled by Gen. Leslie Groves, the head of the Manhattan Project, and did not reach President Truman until after the atomic bombs were used.
The use of the bomb caused many other scientists to despair, as well. Albert Einstein deeply regretted that he had written to President Roosevelt. He did not work on the Manhattan Project, but he had used his influence to encourage the start of the American bomb project. Einstein, like Szilard, believed that the purpose of the US bomb project was to deter the use of a German bomb. He was shocked that, once created, the bomb was used offensively against the Japanese. Einstein would spend the remaining ten years of his life speaking out against the bomb and seeking its elimination. He famously said, "The unleashed power of the atom has changed everything except our modes of thinking, and thus we drift toward unparalleled catastrophe."