The Atomic Bombings of Hiroshima and Nagasaki: The Selection of the Target Summary

  • Last updated on November 10, 2022

In August 1945, the US military used two atomic bombs against the Japanese cities of Hiroshima and Nagasaki. Intended to show Allied military dominance and the futility of a continued war effort by the Japanese, the bombings leveled large parts of the cities and killed more than one hundred thousand people, military and civilian alike. By this time, US air raids had been dropping firebombs throughout much of Japan for months, and intense ground fighting was going on in parts of the Pacific. US leaders realized that defeating Japan would require immense human and economic resources from countries already exhausted by years of war. They hoped to use the devastating force of newly developed atomic weapons to force a rapid end to the war and avoid a lengthy invasion of Japan. Part of the process for achieving this aim, as described in this excerpt, was finding bombing targets that were both strategic and accessible.

Summary Overview

In August 1945, the US military used two atomic bombs against the Japanese cities of Hiroshima and Nagasaki. Intended to show Allied military dominance and the futility of a continued war effort by the Japanese, the bombings leveled large parts of the cities and killed more than one hundred thousand people, military and civilian alike. By this time, US air raids had been dropping firebombs throughout much of Japan for months, and intense ground fighting was going on in parts of the Pacific. US leaders realized that defeating Japan would require immense human and economic resources from countries already exhausted by years of war. They hoped to use the devastating force of newly developed atomic weapons to force a rapid end to the war and avoid a lengthy invasion of Japan. Part of the process for achieving this aim, as described in this excerpt, was finding bombing targets that were both strategic and accessible.

Defining Moment

World War II began in Europe in 1939, but the United States resisted joining the conflict until the Japanese air attack on the US naval base at Pearl Harbor, Hawaii, in December 1941. Although the United States focused many of its resources during its early period of involvement on a strategy to achieve victory in Europe, US sentiment against the Japanese was extremely high throughout the war due to the attack on Pearl Harbor. Fighting against Japanese forces in the Pacific was extremely intense and quite bloody. Beginning in 1942, US troops sought to resist the Japanese in the Philippines, a strategic island nation in the Pacific. But they were largely unsuccessful. In one instance, harsh Japanese treatment of thousands of US prisoners of war in the Philippines resulted in so many casualties that it became known as the Bataan Death March. Japan's aggressive strategies and willingness to employ extreme tactics made it difficult for the United States and its allies to gain a foothold in the region.

As the war in Europe began to turn decisively in favor of the Allies, however, the United States began to recommit to the Pacific theater. US forces began to capture small islands such as Guam from Japanese control in 1944. Troops under General Douglas MacArthur managed to take back control of much of the Philippines from the Japanese in early 1945. From these sites across the Pacific, the US military was able to conduct a series of air raids against mainland Japanese cities. Air raids had been used to great effect by both sides in the war in Europe, and the US campaigns echoed some of the strategies of these earlier efforts; flyers varied tactics and targets in order to surprise the enemy and to cause the most damage possible and had no qualms about using weapons that affected both military and civilian installations. One common air bombing target, for example, were military complexes surrounded by workers' homes. Leaders believed that targets of this nature damaged the Japanese capability to wage war by both eliminating industrial prowess and weakening the morale of the people who were sustaining the war effort. Airplanes equipped with firebombs were particularly devastating. In a single US firebomb attack on Tokyo in March 1945, called Operation Meetinghouse, some one hundred thousand civilians perished.

By the time Allied scientists working on the Manhattan Project perfected the atomic bomb in July 1945, a precedent for using weapons against both military and civilian targets in Japan was already set. Political and military leaders also wanted to achieve a quick victory to stop human and economic resource depletion and to bolster US morale. President Harry S. Truman authorized the atomic bombing of Hiroshima, and this first bombing took place on August 6.

Author Biography

Published by the US Army in the June of 1946, this analysis of the bombings of Hiroshima and Nagasaki drew on research and commentary by numerous military and scientific groups, including the Special Manhattan Engineer District Investigating Group, the US Strategic Bombing Survey, the British Mission to Japan, and the Joint Atomic Bomb Investigating Group. In May 1945, US secretary of war Henry L. Stimson had organized a special committee to study possible applications of the atomic bomb and make recommendations for its usage. Known as the Interim Committee, this group included representatives from the Truman administration, branches of the military, and the Manhattan Project; some of the atomic bombs' main developers, including J. Robert Oppenheimer and Enrico Fermi, contributed to the deliberations. The Interim Committee briefly considered advising against the use of the atomic bomb or suggesting that it be detonated away from a populated area as a demonstration of its power. These strategies were quickly rejected, however, and the committee members turned their attention to identifying ideal military targets. This excerpt from the overall US Army report focuses mostly on the recommendations made by these groups.

Historical Document

Some of the most frequent queries concerning the atomic bombs are those dealing with the selection of the targets and the decision as to when the bombs would be used.

The approximate date for the first use of the bomb was set in the fall of 1942 after the Army had taken over the direction of and responsibility for the atomic bomb project. At that time, under the scientific assumptions which turned out to be correct, the summer of 1945 was named as the most likely date when sufficient production would have been achieved to make it possible actually to construct and utilize an atomic bomb. It was essential before this time to develop the technique of constructing and detonating the bomb and to make an almost infinite number of scientific and engineering developments and tests. Between the fall of 1942 and June 1945, the estimated probabilities of success had risen from about 60% to above 90%; however, not until July 16, 1945, when the first full-scale test took place in New Mexico, was it conclusively proven that the theories, calculations, and engineering were correct and that the bomb would be successful.

The test in New Mexico was held 6 days after sufficient material had become available for the first bomb. The Hiroshima bomb was ready awaiting suitable weather on July 31st, and the Nagasaki bomb was used as soon after the Hiroshima bomb as it was practicable to operate the second mission.

The work on the actual selection of targets for the atomic bomb was begun in the spring of 1945. This was done in close cooperation with the Commanding General, Army Air Forces, and his Headquarters. A number of experts in various fields assisted in the study. These included mathematicians, theoretical physicists, experts on the blast effects of bombs, weather consultants, and various other specialists. Some of the important considerations were:

A. The range of the aircraft which would carry the bomb.

B. The desirability of visual bombing in order to insure the most effective use of the bomb.

C. Probable weather conditions in the target areas.

D. Importance of having one primary and two secondary targets for each mission, so that if weather conditions prohibited bombing the target there would be at least two alternates.

E. Selection of targets to produce the greatest military effect on the Japanese people and thereby most effectively shorten the war.

F. The morale effect upon the enemy.

These led in turn to the following:

A. Since the atomic bomb was expected to produce its greatest amount of damage by primary blast effect, and next greatest by fires, the targets should contain a large percentage of closely-built frame buildings and other construction that would be most susceptible to damage by blast and fire.

B. The maximum blast effect of the bomb was calculated to extend over an area of approximately 1 mile in radius; therefore the selected targets should contain a densely built-up area of at least this size.

C. The selected targets should have a high military strategic value.

D. The first target should be relatively untouched by previous bombing, in order that the effect of a single atomic bomb could be determined.

The weather records showed that for five years there had never been two successive good visual bombing days over Tokyo, indicating what might be expected over other targets in the home islands. The worst month of the year for visual bombing was believed to be June, after which the weather should improve slightly during July and August and then become worse again during September. Since good bombing conditions would occur rarely, the most intense plans and preparations were necessary in order to secure accurate weather forecasts and to arrange for full utilization of whatever good weather might occur. It was also very desirable to start the raids before September.

Document Analysis

One goal of the US Army's report on the atomic bombings of Hiroshima and Nagasaki was to address common questions about relevant strategy and effects, including the choice of targets. This section of the report briefly lays out the consideration given to the target and explains the reasoning behind the selection of Hiroshima and Nagasaki, neither of which were among Japan's most populated cities nor main government centers. Instead, factors ranging from geographic location to climate to architecture shaped the strategic decisions.

The report emphasizes that the need for extensive research and testing made the use of the nuclear weapon impracticable before August 1945. It then summarizes the considerations used to select the bombing targets. The targets had to be accessible to US airplanes carrying the weapons, for example, and located near enough to other suitable sites to allow for the mission to be adjusted should weather impede the planned bombing.

Several characteristics made both Hiroshima and Nagasaki strategically suitable. Hiroshima was untouched by US firebombs; therefore, “the effect of a single atomic bomb could be determined” there as a result. The city housed a large number of military units, and its center contained the “closely-built frame buildings” that military planners rightly estimated “would be most susceptible to damage by blast and fire.” Nagasaki was an industrial and shipping hub that had experienced only a handful of firebombing raids. Although Nagasaki was a secondary target, conditions led bombers to choose the site when the primary target, the city of Kokura, was too clouded for a visual approach.

The report closes by summarizing the constraints on the selection of sites and the timing of the raids. As it had been with the decision to bomb Nagasaki rather than Kokura, weather proved a major factor. Tokyo, as the Japanese capital and largest population center, may have seemed like the most natural strategic target. In order to address any readers who would have preferred this target to be selected for bombing, the report specifically points out that climatic records showed a long history of poor visibility likely to make a bombing there a challenge. Weather also influenced the decision to conduct the bombings in early August, as conditions in September were expected to pose greater challenges to visibility and ground weather. The report, therefore, emphasizes that the decision of when and where to bomb was influenced as much by physical factors as by political ones.

Essential Themes

In the short term, the site selection had significant consequences for the targeted cities and for the country of Japan as a whole. Sizeable portions of both Hiroshima and Nagasaki were destroyed by the force of the atomic detonations and the fires that raged in their wakes; the immediate destruction in Nagasaki was somewhat mitigated by the surrounding mountains, which absorbed the blast waves. The casualties and destruction led to considerable public outcry among the Japanese people, many of whom blamed their own government's aggressive history and refusal to surrender as grounds for the atomic attacks. Combined with the Soviet declaration of war on Japan on August 9, Japan's position after the bombings was untenable, and it agreed to the Allies' terms of surrender.

Hiroshima and Nagasaki faced a daunting task in rebuilding. The bombings destroyed basic infrastructure such as electricity and made transportation routes impassible. Residents of the cities temporarily evacuated while dangerous levels of radiation decreased and supply lines could be established. Reconstruction went on for years, even as some residents of the cities endured illnesses resulting from the intense radioactive exposure they experienced when the bombs were dropped. Unquestionably, the nuclear attacks changed the physical and psychological characteristics of both cities in lasting ways.

As time went on, some of the more ephemeral considerations mentioned in the report came into play on an international scale. The use of the atomic bomb in places relatively untouched by early aerial bombing, and where the psychological and physical effects could thus be most keenly felt, for example, meant that people around the world could readily grasp the bomb's immense destructive power. Political and military leaders in the decades that followed naturally wished to avoid having a similar attack take place on their own soil, and everyday citizens who learned of the bomb's effects feared experiencing such an attack themselves. A significant segment of the global population also came to oppose the use of nuclear weaponry against any target, due to its hugely devastating and irreversible consequences.

Bibliography and Additional Reading
  • Hersey, John. Hiroshima. New York: Knopf, 1946. Print.
  • Hogan, Michael J., ed. Hiroshima in History and Memory. New York: Cambridge UP, 1996. Print.
  • Kort, Michael. Columbia Guide to Hiroshima and the Bomb. New York: Columbia UP, 2007. Print.
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