Pacific War

The Pacific War was the setting in which the atomic bomb ceased to be merely a weapon under construction and became an imminent instrument of policy. Its final months brought together mass civilian destruction, the collapse of the Manhattan Project’s original rationale after Germany’s surrender, and decisions made amid sharp differences in what officials and scientists knew. The war’s end did not close those questions: Hiroshima and Nagasaki turned them into enduring arguments about responsibility, nuclear secrecy, and the public memory of the bomb.

Total war and the fading rationale

As Harry S. Truman moved into the White House, the war in Europe was nearly won, while the Pacific conflict approached its bloodiest climax. On the night of March 9–10, 1945, 334 B-29 aircraft dropped napalm and high explosives on Tokyo. The resulting firestorm killed an estimated 100,000 people and burned out 15.8 square miles of the city. Raids continued; by July, all but five of Japan’s major cities had been razed, and hundreds of thousands of Japanese civilians had been killed. The campaign made the scale of the war’s existing violence impossible to separate from debate over a still more destructive weapon.

That violence was reported openly in American newspapers. J. Robert Oppenheimer later recalled that Henry L. Stimson had found it appalling that the heavy loss of life in the Tokyo air raids had prompted no protest. The concern, as Oppenheimer recounted it, was not simply whether the raids should continue, but what it meant for a country when such destruction went unquestioned. The atomic bomb therefore entered a public and ethical landscape already marked by attacks on cities, even as the decisions about its use remained concentrated among senior officials.

On April 30, Adolf Hitler died by suicide; eight days later, Germany surrendered. At Los Alamos, Emilio Segrè’s first reaction to the news was that the project had come too late. Many there had regarded defeating Hitler as the sole justification for building the bomb. With that rationale gone, doubts arose in private discussions, even when they did not appear in official reports. The change exposed a widening distance between the weapon’s original purpose and the war in which it was now likely to be used.

Competing efforts to shape the decision

Leo Szilard, who had earlier urged Franklin D. Roosevelt to begin an atomic-weapons program, now tried repeatedly to prevent the bomb’s use. He warned that an atomic demonstration could precipitate an arms race with the Soviet Union. After Roosevelt died before Szilard could meet him, Szilard sought an appointment with Truman and wrote to Oppenheimer that, without a clear policy to avoid such a race, using the bomb against Japan was unwise. Oppenheimer did not reply. After another failed effort to halt use of the weapon, Szilard worked to establish a public record that a vocal minority of Manhattan Project scientists had opposed using it against a civilian target.

On May 31, Oppenheimer attended a meeting of Henry L. Stimson’s Interim Committee, which advised the secretary of war on atomic policy. The meeting did not decide whether the bomb should be used against Japan; that question was treated as effectively settled and under White House control. The committee nevertheless discussed the weapon’s far-reaching consequences. Oppenheimer and other scientists heard Stimson describe it not merely as a new weapon but as a revolutionary change in humanity’s relation to the universe, capable of becoming a Frankenstein or of helping secure global peace.

The committee’s discussion also exposed a conflict over sharing information with the Soviet Union. George C. Marshall considered whether Russian scientists might be invited to witness a test, while James F. Byrnes objected that such access might lead Stalin to demand entry into the atomic project. Oppenheimer had argued against prejudging the Russian response, and the scientists understood that the bomb’s underlying physics could not remain secret indefinitely. Byrnes instead pressed for faster production and research to preserve American superiority. The committee accepted that position in its minutes, while leaving unresolved the contradiction between an effort to stay ahead and the risk that doing so would drive a Soviet arms race.

What decision-makers knew—and what Los Alamos did not

Oppenheimer later said that the scientists did not know enough about Japan’s military position to judge whether surrender could be achieved by other means. In particular, he did not know that intercepted and decoded Japanese communications, known as Magic, showed that the government was seeking acceptable terms. On May 28, John J. McCloy urged that the demand for unconditional surrender be dropped; Joseph C. Grew gave Truman similar advice. Japanese officials’ central concern was retaining their emperor and a form of government.

Further warnings and alternatives reached Truman in June and July. William D. Leahy wrote that Japan might surrender on acceptable terms. McCloy advised Truman to clarify that Japan could retain its emperor and to warn that the United States possessed a terrifying weapon it would use if Japan did not surrender. Dwight D. Eisenhower later recalled telling Stimson at the Potsdam Conference that an atomic attack was unnecessary because Japan was ready to surrender. Truman’s diary also recorded a Japanese appeal for peace and his expectation that the Soviet Union’s entry into the war would help bring Japan to terms.

The first planned invasion of the Japanese home islands was not scheduled before November 1, 1945, and many advisers expected the war to end sooner, either through Soviet intervention or a change in surrender terms. Truman and Byrnes, however, wanted the war ended before the Soviet Union entered it. Byrnes opposed clarifying the surrender terms on domestic political grounds; in that context, atomic use offered another way to end the war before Soviet involvement. Oppenheimer, isolated at Los Alamos, knew neither about the intercepted messages nor about the arguments over surrender terms and Soviet entry. The disparity between what he knew and what officials in Washington were weighing is central to the uncertainty surrounding the scientists’ endorsement of military use.

The bomb’s aftermath and its public memory

After the Trinity test, Oppenheimer recalled the Bhagavad-Gita as he watched the cloud rise, remembering its line, “Now I am become death, the destroyer of worlds.” The recollection later became one of the most enduring public frames for the bomb. It stood alongside the immediate reactions of those present and, later, the physical evidence brought back by observers from Hiroshima and Nagasaki.

In October, Robert Serber and Philip Morrison returned with the first group of scientific observers. Morrison described severe burns across the streets near the Hiroshima blast and deaths that followed days or weeks after people had crawled from damaged homes. Serber recalled telephone poles charred on the sides facing the Nagasaki explosion, and a horse whose hair was burned from one side of its body. When Serber described the animal as happily grazing, Oppenheimer reprimanded him for making the bomb sound benevolent. Morrison’s account of Hiroshima emphasized the transformation wrought by a single bomb: a city of 300,000 turned into a burning ruin in the time it took a rifle bullet to cross it.

Those reports affected people at Los Alamos, including Oppenheimer and Katherine (Kitty) Oppenheimer. Morrison’s account left one listener unable to sleep; others gathered to try to comprehend what had happened. Scientists began arguing that nuclear energy could not simply be left in the hands of military officers and political leaders. Oppenheimer also came to describe the wartime mobilization as a ruthless exploitation of existing knowledge that had stopped physics rather than advanced it. The weapon’s accomplishment thus appeared to him not only as a human catastrophe but as a distortion of the scientific work that had made it possible.

The Pacific War remained a point of reference in later disputes over nuclear strategy. In 1949, Oppenheimer and the General Advisory Committee argued that a thermonuclear weapon capable of destroying hundreds of square miles would risk becoming a weapon of genocide, and that refusing to build one might reopen arms-control negotiations. In 1951, he helped give priority to tactical weapons in the Project Vista analysis as an alternative to plans for massive attacks on cities, though that choice also risked making nuclear weapons more usable in battle. His later public recollections kept the wartime decision in view: in a 1965 television documentary he recited the Bhagavad-Gita passage, and he said that talks to halt nuclear proliferation should have begun the day after Trinity. In this way, the Pacific War persisted in the book not only as the setting for atomic use, but as the unresolved measure against which later policy and remembrance were judged.