The Pacific Theater and the Atomic Bomb


All belligerents in World War II sought to develop powerful and devastating weaponry. As early as 1939, German scientists had discovered how to split uranium atoms, the technology that would ultimately allow for the creation of the atomic bomb. Albert Einstein, who had emigrated to the United States in 1933 to escape the Nazis, urged President Roosevelt to launch an American atomic research project, and Roosevelt agreed to do so, with reservations. In late 1941, the program received its code name: the Manhattan Project. Located at Los Alamos, New Mexico, the Manhattan Project ultimately employed 150,000 people and cost some $2 billion. In July 1945, the project’s scientists successfully tested the first atomic bomb.

In the spring of 1945, the military began to prepare for the possible use of an atomic bomb by choosing appropriate targets. Suspecting that the immediate bomb blast would extend over one mile and secondary effects would include fire damage, a compact city of significant military value with densely built frame buildings seemed to be the best target. Eventually, the city of Hiroshima, the headquarters of the Japanese Second Army, and the communications and supply hub for all of southern Japan, was chosen. The city of Kokura was chosen as the primary target of the second bomb, and Nagasaki, an industrial center producing war materiel and the largest seaport in southern Japan, was selected as a secondary target.

The Enola Gay, a B-29 bomber named after its pilot’s mother, dropped an atomic bomb known as “Little Boy” on Hiroshima at 8:15 a.m. Monday morning, August 6, 1945. A huge mushroom cloud rose above the city. Survivors sitting down for breakfast or preparing to go to school recalled seeing a bright light and then being blown across the room. The immense heat of the blast melted stone and metal, and ignited fires throughout the city. One man later recalled watching his mother and brother burn to death as fire consumed their home. A female survivor, a child at the time of the attack, remembered finding the body of her mother, which had been reduced to ashes and fell apart as she touched it. Two-thirds of the buildings in Hiroshima were destroyed. Within an hour after the bombing, radioactive “black rain” began to fall. Approximately seventy thousand people died in the original blast. The same number would later die of radiation poisoning. When Japan refused to surrender, a second atomic bomb, named Fat Man, was dropped on Nagasaki on August 9, 1945. At least sixty thousand people were killed at Nagasaki. Kokura, the primary target, had been shrouded in clouds on that morning and thus had escaped destruction. It is impossible to say with certainty how many died in the two attacks; the heat of the bomb blasts incinerated or vaporized many of the victims (Figure).

Photograph (a) shows a massive mushroom cloud created by an atomic bomb. Photograph (b) shows the ruins of Hiroshima, with only the shell of a domed building left standing among the rubble.
According to estimates, the atomic bombs dropped on Hiroshima and Nagasaki (a) together killed anywhere from 125,000 to over 250,000 people. The so-called Genbaku (A-Bomb) Dome, now the Hiroshima Peace Memorial, was the only building left standing near the Hiroshima bomb’s hypocenter (b).

Visit the Atomic Bomb Museum site to read the accounts of survivors Hiroshi Morishita and Shizuko Nishimoto.

The decision to use nuclear weapons is widely debated. Why exactly did the United States deploy an atomic bomb? The fierce resistance that the Japanese forces mounted during their early campaigns led American planners to believe that any invasion of the Japanese home islands would be exceedingly bloody. According to some estimates, as many as 250,000 Americans might die in securing a final victory. Such considerations undoubtedly influenced President Truman’s decision. Truman, who had not known about the Manhattan Project until Roosevelt’s death, also may not have realized how truly destructive it was. Indeed, some of the scientists who had built the bomb were surprised by its power. One question that has not been fully answered is why the United States dropped the second bomb on Nagasaki. As some scholars have noted, if Truman’s intention was to eliminate the need for a home island invasion, he could have given Japan more time to respond after bombing Hiroshima. He did not, however. The second bombing may have been intended to send a message to Stalin, who was becoming intransigent regarding postwar Europe. If it is indeed true that Truman had political motivations for using the bombs, then the destruction of Nagasaki might have been the first salvo of the Cold War with the Soviet Union. And yet, other historians have pointed out that the war had unleashed such massive atrocities against civilians by all belligerents—the United States included—that by the summer of 1945, the president no longer needed any particular reason to use his entire nuclear arsenal.