21. Heroes and Villains from World War II: The Atomic Bomb and Defeating Japan (1938–1945)

My Name is J. Robert Oppenheimer: Scientific Director of Los Alamos

I was born in New York City in 1904 into a family that valued education, art, literature, and careful thought. From childhood, I was fascinated by the natural world. Minerals first captured my attention, but eventually I became consumed by questions far smaller than any stone I could hold: What is matter made of? What laws govern the invisible world inside the atom? I studied at Harvard and later traveled to Europe, where I worked among some of the greatest physicists of my generation. The new science of quantum mechanics was transforming our understanding of nature, and I wanted to stand at its frontier.

Becoming an American Physicist

When I returned to the United States, I taught physics at the University of California, Berkeley, and the California Institute of Technology. I was not primarily an experimental physicist; my strength was theoretical physics—the mathematics and ideas that allowed us to predict what experiments might reveal. During the 1930s, however, science could not remain separated from politics. Hitler rose in Germany, Jewish scholars were driven from their universities, and many brilliant European scientists fled to Britain and America. Then came a discovery with frightening possibilities: nuclear fission. The nucleus of an atom could be split, releasing tremendous energy.

The Fear of a German Bomb

When war consumed Europe, physicists understood what nuclear fission might mean. If a chain reaction could be controlled, it might produce energy. If it could be made extraordinarily rapid, it might produce an explosion of unprecedented power. Germany possessed excellent scientists, and we did not know how far its atomic research had progressed. The possibility that Hitler's government might obtain such a weapon could not simply be ignored. The United States therefore assembled an enormous secret undertaking that became known as the Manhattan Project.

Los Alamos

In 1942, General Leslie Groves asked me to lead the laboratory where the bomb itself would be designed. We established it at Los Alamos, New Mexico, on an isolated mesa surrounded by mountains and desert. Scientists arrived from across America and Europe. Hans Bethe, Enrico Fermi, Edward Teller, Richard Feynman, and many others became part of an extraordinary concentration of scientific talent. Our challenge was no longer simply theoretical. We had to transform equations written on blackboards into a weapon that would actually function.

Building the Impossible

Two different atomic bombs emerged from our work. One used uranium-235 and became known as Little Boy. The other used plutonium and required an extraordinarily difficult implosion mechanism in which explosives surrounding a plutonium core had to detonate with remarkable precision. That weapon became Fat Man. Elsewhere, Oak Ridge produced enriched uranium while Hanford manufactured plutonium. Los Alamos brought these efforts together. The project was science, engineering, industry, and military organization operating on a scale I had never imagined.

The Morning the Desert Turned to Light

Before dawn on July 16, 1945, we gathered in the New Mexico desert for the Trinity test. Rain and lightning had swept across the area. Then, at 5:29 in the morning, the device exploded. The darkness vanished beneath an enormous flash. A fireball climbed upward, followed by the great cloud that would become one of the defining images of the twentieth century. Years later, I recalled a line from the Bhagavad Gita: "Now I am become Death, the destroyer of worlds." At that moment, however, we were also scientists watching an experiment succeed. The weapon worked.

Hiroshima and Nagasaki

Germany had already surrendered, but the Pacific War continued. American forces had suffered terrible casualties at Iwo Jima and Okinawa, and preparations were underway for a possible invasion of Japan. The decision to use the bombs belonged to President Harry Truman and the American government, not to me. On August 6, 1945, Little Boy was dropped on Hiroshima. Three days later, Fat Man devastated Nagasaki. Japan soon accepted surrender. The war that had killed millions across the world was finally coming to an end, but another age had begun.

What We Had Created

After the war, I became one of America's most prominent scientific advisers and eventually chaired the General Advisory Committee of the Atomic Energy Commission. I argued for international control of atomic energy and opposed rushing directly into development of the hydrogen bomb. During the tensions of the Cold War, my political associations and positions brought suspicion upon me. In 1954, after a highly controversial security hearing, my security clearance was revoked. I continued teaching, writing, and speaking about science until my death in 1967.

Fear That Nazi Germany Might Get There First (1940) - Told by Oppenheimer

In December 1938, German chemists Otto Hahn and Fritz Strassmann conducted experiments with uranium and discovered results they could not adequately explain. Their former colleague Lise Meitner, a brilliant Jewish-born physicist who had fled Nazi Germany's annexation of Austria, and her nephew Otto Frisch correctly interpreted what had happened: the uranium nucleus had split. Frisch soon called the process nuclear fission. To physicists, this was astonishing. Splitting an atom's nucleus released an extraordinary amount of energy. Almost immediately another question appeared: could one splitting nucleus release neutrons that split others, creating a self-sustaining chain reaction?

The Scientists Hitler Drove Away

There was a bitter irony in Germany's position. Adolf Hitler's racial policies had driven many outstanding scientists from Germany and Nazi-controlled Europe. Albert Einstein had left Germany after Hitler came to power. Leo Szilard, a Hungarian Jewish physicist who had already considered the possibility of a nuclear chain reaction, also fled. Edward Teller and Eugene Wigner left Europe for America, while Enrico Fermi departed Fascist Italy after receiving the 1938 Nobel Prize; his wife, Laura, was Jewish. These refugees understood European science intimately. They also understood the governments from which they had escaped. When news of nuclear fission spread, they did not see only an exciting scientific discovery. They saw a possible weapon.

What If Germany Built It First?

Germany possessed respected physicists, uranium resources in occupied Europe, and a sophisticated scientific tradition. Werner Heisenberg, one of the world's leading theoretical physicists, remained in Germany and became involved in its wartime nuclear research. We did not know how far the Germans would go or whether an atomic bomb was actually practical. That uncertainty was precisely the problem. Imagine Hitler possessing a bomb capable of destroying the center of London—or perhaps someday an American city. We could not simply assume that German scientists would fail.

Einstein Receives a Warning

Leo Szilard understood that American political leaders needed to hear about the danger. Working with Eugene Wigner and later Edward Teller, he approached Albert Einstein during the summer of 1939. Einstein's fame gave the warning a political weight that most physicists could never command. Szilard helped draft a letter that Einstein signed on August 2, 1939, addressed to President Franklin D. Roosevelt. It explained that uranium might make possible extremely powerful bombs and warned that Germany had taken steps concerning uranium from Czechoslovakian mines.

A Letter Reaches the President

Economist Alexander Sachs personally delivered the letter's warning to Roosevelt in October 1939, after Germany had already invaded Poland and begun the European war. Roosevelt responded by establishing an advisory committee on uranium. At first, America's atomic effort was modest. Nuclear physics was still filled with unanswered questions. Scientists had to determine whether a chain reaction was possible, how suitable uranium isotopes could be separated, and whether enough fissile material could ever be manufactured to create a bomb.

The Evidence Grows

During 1940 and 1941, the scientific case became stronger. Researchers in Britain concluded through the MAUD Committee that an atomic bomb might actually be practical and urged serious development. In America, scientists studied uranium-235 while research into the newly discovered element plutonium opened another possible path toward a weapon. The question was changing. We were no longer asking merely whether an atomic bomb belonged to the realm of theoretical possibility. We were beginning to ask whether one could be built soon enough to matter in this war.

America Enters the Race

Then came December 7, 1941. Japan attacked Pearl Harbor, and the United States entered World War II. Germany declared war on America days later. Scientific research was now inseparable from national survival. During 1942, the American atomic program accelerated dramatically. Enrico Fermi's team constructed Chicago Pile-1 beneath the stands of the University of Chicago's Stagg Field. On December 2, they achieved the world's first controlled, self-sustaining nuclear chain reaction. Something that had existed largely in calculations and laboratory experiments was now demonstrably real.

Scientists Flee Hitler and Bring Their Knowledge - Told by Oppenheimer

By the time I gathered scientists at Los Alamos, Hitler had already committed one of the greatest strategic blunders imaginable. Nazi Germany had inherited one of the finest scientific traditions in the world, yet its racial laws and political persecution drove brilliant minds from German universities and across Europe. Many were Jewish. Others opposed fascism or fled countries threatened by Nazi expansion. They carried something Hitler could not confiscate at a border: knowledge. Eventually, some of that knowledge would become part of the Allied effort to build the atomic bomb.

Leo Szilard Sees the Possibility

Leo Szilard was born in Budapest and possessed one of those restless minds that seemed always several steps ahead. After Hitler came to power in 1933, Szilard left Germany for Britain and eventually moved to the United States. Even before nuclear fission was discovered, he had imagined the possibility of a nuclear chain reaction. When scientists learned in 1939 that uranium atoms could split and release neutrons, Szilard immediately understood the frightening implication. Those neutrons might split additional atoms, releasing still more neutrons and energy. Szilard helped persuade Albert Einstein to warn President Roosevelt that Germany might attempt to build an atomic weapon.

Teller and Wigner Escape Hungary

Edward Teller and Eugene Wigner were also Hungarian-born Jewish physicists who left an increasingly dangerous Europe. Wigner became one of the important figures in reactor theory and helped design the nuclear reactors that would produce plutonium for the Manhattan Project. Teller joined us at Los Alamos and worked on atomic-bomb calculations, although his imagination was already reaching toward an even more powerful possibility: a weapon based on nuclear fusion. These men did not arrive in America as Germans captured after the war. They had chosen to leave Europe before or during the conflict and then contributed voluntarily to the Allied scientific effort.

Hans Bethe Becomes My Theoretical Chief

Hans Bethe had been born in Strasbourg when it belonged to the German Empire. His mother was Jewish, and Nazi racial laws cost him his university position after Hitler came to power. Bethe left Germany and eventually settled in the United States. When I needed someone to lead the Theoretical Division at Los Alamos, I chose him. It was an excellent decision. Bethe possessed both extraordinary mathematical ability and the discipline necessary to organize difficult scientific work. His division calculated what would happen during the incredibly brief moments when an atomic bomb's nuclear chain reaction raced toward explosion.

Enrico Fermi Leaves Fascist Italy

Enrico Fermi's escape was different. He was Italian, not German, and already one of the world's greatest experimental physicists. Mussolini's government adopted antisemitic racial laws in 1938, threatening Fermi's family because his wife, Laura, was Jewish. That same year Fermi traveled to Stockholm to receive the Nobel Prize in Physics. Instead of returning permanently to Italy, the family continued to the United States. Four years later, beneath the stands of the University of Chicago's Stagg Field, Fermi directed Chicago Pile-1. On December 2, 1942, his team achieved the world's first controlled, self-sustaining nuclear chain reaction. The atomic age had moved from theory toward engineering.

The Refugees Become an Allied Advantage

These were only some of the European scientists who strengthened Allied research. The movement of scientists across the Atlantic created an extraordinary concentration of knowledge in Britain, Canada, and the United States. At Los Alamos, accents from across Europe mixed with those of American-born physicists. We argued over equations, explosives, neutron behavior, metallurgy, and bomb design. The irony was impossible to miss: persecution intended to purify Nazi-controlled Europe had helped send scientific talent directly into the nations fighting Hitler.

Not Operation Paperclip

There is an important distinction students should understand. These wartime émigré scientists were not the same as the Germans brought to the United States through Operation Paperclip. Paperclip developed after Nazi Germany's defeat in 1945, when the United States recruited German scientists and engineers, including Wernher von Braun and members of his rocket team. Their expertise became especially important to American missile and space programs. Some had troubling or serious connections to the Nazi regime and its wartime system.

The scientists who helped create the Manhattan Project's bombs had a different story. Szilard, Teller, Wigner, Bethe, Fermi, and others had reached the Allied world before the war ended, often because fascist governments had threatened their careers, freedom, or families.

Hitler's Scientific Gift to His Enemies

History contains strange reversals. Nazi Germany frightened us into believing that Hitler might obtain an atomic bomb first, while Nazi persecution simultaneously drove gifted scientists into the Allied camp. Germany ultimately did not come close to producing an operational atomic weapon during the war. We did not know that while we were working.

My Name is General Leslie R. Groves: Director of the Manhattan Project

I was born in Albany, New York, in 1896, the son of an Army chaplain. Military life was familiar to me from childhood, and I eventually entered the United States Military Academy at West Point, graduating in 1918. I became an officer in the Army Corps of Engineers. I learned early that large projects are not completed by good intentions. They require organization, discipline, resources, competent people, and someone willing to make decisions.

Building for War

Before the Manhattan Project, I supervised major military construction as the United States prepared for World War II. Among the projects under my authority was construction of the Pentagon. It was an enormous undertaking, exactly the sort of assignment that taught me how to coordinate contractors, engineers, government officials, supplies, money, and deadlines. In wartime, delay could be as dangerous as failure.

A Secret Assignment

In September 1942, I was placed in charge of what became the Manhattan Engineer District—the Manhattan Project. The objective was extraordinary: develop an atomic bomb before our enemies could. Germany had outstanding physicists and had discovered nuclear fission before the war. We did not know precisely how advanced the German atomic program was. That uncertainty was enough. If such a weapon could be built, the United States could not afford to finish second.

Choosing Oppenheimer

One of my most important decisions was selecting J. Robert Oppenheimer to direct the scientific laboratory at Los Alamos. He was not the obvious military choice. He had limited administrative experience and associations that concerned security officials. But I believed he possessed something more important: he understood the physics, knew the scientists, and could bring strong personalities together. I approved him despite the objections. A commander must sometimes choose the person capable of accomplishing the mission rather than the person whose paperwork is most comfortable.

Building a Secret Industrial Empire

The Manhattan Project became much larger than a laboratory in New Mexico. At Oak Ridge, Tennessee, enormous facilities worked to separate uranium-235. At Hanford, Washington, reactors produced plutonium. At Los Alamos, scientists designed the weapons. Factories, laboratories, mines, railroads, electrical systems, and military units were connected to a project so secret that many workers did not know what they were helping create. At its height, the enterprise employed more than 100,000 people and cost roughly $2 billion in wartime dollars.

Trinity

On July 16, 1945, we tested the plutonium implosion design in the New Mexico desert. The test was called Trinity. I watched from a bunker as years of work came down to a single moment. When the device exploded, the desert was illuminated by a tremendous flash and the shock wave rolled outward. For the scientists, it was an astonishing scientific achievement. For me, it answered the essential military question: the weapon worked. Now it could be used.

Selecting the Targets

Even before Trinity, military officials and scientists had studied potential Japanese targets. Hiroshima, Kokura, Niigata, and Kyoto were among those considered at various stages. Kyoto was eventually removed from consideration after Secretary of War Henry Stimson strongly opposed attacking the culturally significant city. Hiroshima remained a major target because of its military importance, size, and relatively limited previous bombing damage, which would make the effects of the new weapon easier to assess. These were grim calculations, but we were fighting a war in which cities throughout Europe and Asia had already suffered terrible destruction.

The Bombs Are Used

On August 6, 1945, the uranium bomb Little Boy was dropped on Hiroshima. Three days later, the plutonium bomb Fat Man was dropped on Nagasaki after clouds and smoke prevented the mission from bombing its primary target, Kokura. The destruction was enormous. At nearly the same time, the Soviet Union entered the war against Japan. Within days, Japan announced that it would surrender. The Manhattan Project had fulfilled the military purpose for which it had been created.

America's Secret Industrial Empire (1942–1945) - Told by General Leslie Groves

When I took command of the Manhattan Engineer District in September 1942, I was not being asked simply to supervise a laboratory. The United States intended to build an entirely new industry before our enemies could understand what we were doing. Scientists believed an atomic bomb might be possible, but theories and equations would not win the war. We needed factories, electrical power, laboratories, construction crews, transportation, security, and enormous quantities of materials. Most important, we needed all of it quickly—and secretly.

Three Secret Cities

The project eventually centered on three remarkable locations. Oak Ridge, Tennessee, would produce enriched uranium. Hanford, Washington, would manufacture plutonium. Los Alamos, New Mexico, would design and assemble the weapons themselves. Each site had a different purpose, but all three had to work together. We selected isolated locations where we could obtain land, electricity, water, transportation, and enough distance from major population centers to maintain security.

Oak Ridge alone became an extraordinary industrial complex. Its facilities used several methods to separate uranium-235 from the much more common uranium-238. The enormous K-25 gaseous-diffusion plant became one of the largest buildings constructed under one roof at the time. Another facility, Y-12, used electromagnetic separation. The amount of electricity required was tremendous, but the Tennessee Valley Authority provided access to the power we needed.

Creating Plutonium at Hanford

In Washington State, along the Columbia River, we built the Hanford Engineer Works. Here the challenge was different. Rather than separating naturally occurring uranium-235, reactors would transform uranium into plutonium that could later be chemically separated and used in a bomb. The site required huge reactors, chemical-processing facilities, cooling water, electrical systems, and communities for the workers constructing and operating them.

Nothing quite like it had existed before. We were building industrial-scale nuclear reactors while nuclear science itself was still young. Engineers sometimes had to design machinery before scientists had completely settled how the underlying process would work. Construction and research therefore moved forward simultaneously. Waiting until every uncertainty disappeared was not an option.

Oppenheimer's Laboratory in the Desert

The material produced at Oak Ridge and Hanford would be useless unless someone could transform it into functioning weapons. For that job, we established a laboratory on an isolated mesa at Los Alamos, New Mexico. I selected J. Robert Oppenheimer as its scientific director.

Los Alamos attracted an extraordinary collection of physicists, chemists, mathematicians, engineers, explosives specialists, and military personnel. Their task was to solve the problems of bomb design. Eventually, they developed two different approaches: a relatively straightforward uranium gun-type weapon and a far more complicated plutonium implosion weapon.

A Nation Working Without Knowing Why

The Manhattan Project ultimately employed roughly 130,000 people at its peak, yet only a small fraction understood the entire mission. A worker at Oak Ridge might operate equipment every day without knowing what the material being produced would eventually become. Construction workers erected enormous buildings without being told their ultimate purpose. Secretaries typed reports containing only the information necessary for their jobs. Soldiers guarded facilities whose true mission they might not know.

We operated on the principle of compartmentalization. People were generally told what they needed to perform their duties and little more. Even Vice President Harry Truman was not fully informed about the atomic project before becoming president. Maintaining secrecy across an enterprise of this size was one of our greatest organizational challenges.

Two Billion Dollars Hidden in a War

By the end of the war, the Manhattan Project had cost approximately $2 billion in 1940s dollars—an enormous sum, equivalent to tens of billions in modern purchasing power depending on the comparison used. Much of that money did not go into the bombs themselves. It paid for industrial plants, towns, laboratories, electrical systems, reactors, raw materials, research, and an immense workforce.

Congress provided the necessary wartime funding while only a small number of legislators knew exactly what the project was building. We were creating an industrial empire hidden inside an even larger global war.

From Factories to a Flash in the Desert

By 1945, the pieces were finally coming together. Oak Ridge was producing enriched uranium. Hanford was supplying plutonium. Los Alamos was turning those materials into weapons. On July 16, 1945, we tested the plutonium implosion design at Trinity in the New Mexico desert. The explosion proved that the vast system we had constructed could accomplish its purpose.

Los Alamos: Turning Atomic Theory into a Weapon - Told by Oppenheimer

In the spring of 1943, scientists began gathering on an isolated mesa in northern New Mexico for an assignment unlike anything attempted before. I had been chosen to direct the laboratory at Los Alamos. General Leslie Groves wanted secrecy, speed, and results. I wanted the finest scientific minds we could assemble. Somewhere between his military demands and our blackboards filled with equations, we had to transform nuclear fission from an extraordinary discovery into an actual weapon.

A Laboratory Behind the Fence

Los Alamos became a strange wartime community. Hans Bethe directed theoretical work. Robert Bacher supervised experimental physics. George Kistiakowsky became crucial to our explosives program. Enrico Fermi arrived later and contributed his remarkable understanding of nuclear reactions. Richard Feynman was still a young physicist, yet already displayed the restless intelligence for which he would become famous. Scientists lived with their families behind guarded gates while letters were censored and our location was concealed from much of the outside world.

We knew why we had been brought together. The possibility of a German atomic bomb remained an important motivation during much of the project. We could not know with confidence how advanced Germany's nuclear work was, and so our assignment carried an unmistakable urgency.

The Uranium Bomb

One path toward the bomb appeared relatively straightforward. If enough uranium-235 could be obtained, two subcritical pieces could be rapidly brought together to form a supercritical mass. A nuclear chain reaction would then multiply with extraordinary speed.

The resulting weapon became Little Boy. Its design used a gun-type mechanism to drive one piece of uranium into another. We had considerable confidence that the concept would work, so the completed uranium bomb was never tested in a full nuclear explosion before Hiroshima. The greater difficulty was obtaining enough uranium-235. That responsibility fell largely to the enormous enrichment facilities at Oak Ridge, Tennessee.

Plutonium Gives Us a Crisis

Plutonium initially seemed to offer another route using a similar gun-type design. Then measurements of reactor-produced plutonium revealed a serious problem. It contained more plutonium-240 than expected, producing spontaneous neutrons at a rate that could cause a gun-type plutonium weapon to begin its chain reaction too early. Instead of the enormous explosion we wanted, the weapon might partially destroy itself before reaching its full potential.

It was one of the project's most dangerous technical setbacks. A design on which we had spent valuable time was no longer practical. We had plutonium coming from Hanford, but we needed an entirely different way to use it.

The Implosion Problem

The solution was implosion. Instead of firing one piece of material into another, we would surround a plutonium core with carefully arranged conventional explosives. When detonated, those explosives had to produce an inward-moving shock wave that compressed the plutonium rapidly and symmetrically into a supercritical state.

That sentence makes the task sound considerably easier than it was. Explosive waves do not naturally behave with perfect symmetry. If one section moved inward too quickly or another too slowly, the core could deform and the weapon could fail. We developed explosive lenses that shaped the detonation waves and worked on electrical detonators capable of firing with extremely precise timing. Experiments failed. Designs changed. Arguments filled meeting rooms. Then we tested again.

The Bomb Takes Shape

By 1944, Los Alamos reorganized much of its effort around solving the implosion problem. Mathematicians calculated shock waves. Chemists studied plutonium. Metallurgists struggled with a metal whose properties were remarkably complicated. Explosives experts refined the lenses. Physicists calculated how neutrons would behave during the few millionths of a second in which the nuclear reaction developed.

Gradually, the impossible began to look possible. The uranium design evolved toward Little Boy. The plutonium implosion design became the weapon later called Fat Man. Yet unlike Little Boy, we could not simply trust the implosion weapon to work. It was too complicated. We would have to test it.

Germany Surrenders

Then the purpose that had originally driven many of us changed. Allied investigators were discovering that Germany's atomic program had been far behind ours. Nazi Germany surrendered in May 1945, but our bombs were nearing completion and the war against Japan continued.

That produced uncomfortable discussions among scientists. Some believed using the bomb could end the Pacific War quickly. Others questioned whether Japan should first receive a demonstration or warning. Leo Szilard and other scientists raised objections and sought greater consideration of the consequences. The Franck Report, written by scientists at the Metallurgical Laboratory in Chicago, warned about the political and international dangers of beginning the atomic age by using the weapon without prior demonstration.

Trinity: The World's First Atomic Explosion — July 1945 - Told by Oppenheimer

Before dawn on July 16, 1945, I stood in the New Mexico desert waiting to learn whether years of secret work would succeed in a fraction of a second. Around us stretched the Jornada del Muerto, the "Journey of the Dead Man," an isolated desert basin chosen for the first full-scale test of an atomic weapon. On a steel tower roughly 100 feet high sat the device we called the Gadget. Inside it was a plutonium core surrounded by an intricate implosion system. If our calculations were correct, we were about to release energy from the atomic nucleus on a scale no human being had ever witnessed.

The Problem We Had to Solve

Our plutonium weapon was far more complicated than the uranium design that became Little Boy. Reactor-produced plutonium could not reliably be used in the simpler gun-type design because spontaneous neutrons could begin the reaction too soon. We therefore had to compress a plutonium core almost perfectly from every direction using precisely shaped conventional explosives. If the explosive lenses or detonators fired unevenly, the core might fail to achieve the necessary supercritical state. Months of calculations and experiments had brought us here, but no one had ever tested the complete system in a nuclear explosion.

Waiting Under a Storm

The test was originally planned for around 4:00 in the morning, but thunderstorms moved across the desert. Rain fell, lightning flashed, and General Leslie Groves worried about radioactive material being carried by unfavorable weather if the test proceeded. We waited.

I was tense. Years later, Groves remembered that I seemed extremely nervous and exhausted. Some scientists had jokingly taken bets on the explosive yield. Enrico Fermi even prepared a simple experiment involving scraps of paper to estimate the strength of the blast from the movement of the air. Beneath the humor was genuine uncertainty. We believed the device would work, but science does not surrender its answer simply because one desperately wants it.

5:29:45 A.M.

At 5:29:45 in the morning, the countdown reached zero. The desert became light.

For an instant, the flash was brighter than anything I had ever experienced. Even observers miles away felt its intensity. A tremendous fireball formed where the tower had stood and expanded upward. Seconds later came the shock wave, followed by the great rising cloud that would become inseparable from the atomic age. Fermi dropped his scraps of paper and watched how far the blast moved them. Instruments recorded what human senses could only struggle to comprehend.

The explosion produced a yield of roughly 21 kilotons of TNT. The steel tower was effectively destroyed, and the intense heat fused desert sand and other materials into a glassy substance later called trinitite.

The Scientists React

Reactions around me varied. Some men shouted. Others laughed or shook hands. Years of extraordinary pressure had ended in success. George Kistiakowsky, who had worked so hard on the explosive system, came to me after the test; our implosion design had functioned.

For a scientist, there was undeniable exhilaration in seeing theory, mathematics, chemistry, metallurgy, and engineering come together successfully. We had attempted something that only a few years earlier had seemed almost unimaginable. But the celebration could not entirely conceal what we had demonstrated.

A Line from Ancient India

People often associate that morning with words I later recalled from the Bhagavad Gita: "Now I am become Death, the destroyer of worlds." I did not announce those words dramatically as the bomb exploded; the famous recollection came years afterward when I described what passed through my mind.

Another passage was also associated with my memory of Trinity: "If the radiance of a thousand suns were to burst at once into the sky..." Ancient language seemed better suited than ordinary scientific vocabulary to describe what we had witnessed. Our equations could explain the reaction. They could not easily explain the feeling of standing before it.

A Message for Truman

The Trinity test also had immediate military and political consequences. President Harry Truman was at the Potsdam Conference in Germany with Allied leaders when news of the successful test reached him. The United States no longer possessed merely an experimental program. It possessed a functioning atomic weapon.

Japan was still fighting. American planners were preparing for possible invasion. The Soviet Union was preparing to enter the Pacific War. Decisions about how the atomic bomb would be used were moving rapidly toward their conclusion.

The Atomic Age Begins

When the sun rose over New Mexico that morning, the landscape looked much as it had before. Mountains still surrounded the desert. The sky eventually cleared. Men packed equipment, examined instruments, and began studying the results. Yet the world was not the same.

My Name is Harry S. Truman: President of the United States

I was born in Lamar, Missouri, in 1884 and grew up in Independence. I was not born into wealth or national importance. I worked on my family's farm, held ordinary jobs, and learned that responsibility generally comes before recognition. When America entered the First World War, I served as an artillery officer in France. Commanding men under fire taught me something I carried into politics: when the responsibility is yours, you make the decision and accept the consequences.

A Missouri Politician

After the war, I entered business and then politics. My first business failed, leaving me with debts I worked for years to repay. Eventually, I served as a county judge and then, in 1934, Missouri voters elected me to the United States Senate. During World War II, I became known nationally for leading a Senate committee investigating waste and mismanagement in America's enormous defense program. I believed the government owed taxpayers results, especially when American soldiers were risking their lives overseas.

Suddenly President

In 1944, Franklin D. Roosevelt selected me as his vice-presidential running mate. I had been vice president for only eighty-two days when Roosevelt died on April 12, 1945. Suddenly, I was President of the United States. The war in Europe was nearing its end, but the fighting against Japan remained fierce. Then Secretary of War Henry Stimson told me about an undertaking of extraordinary secrecy: the United States was developing an atomic bomb.

The War Against Japan

By the summer of 1945, Germany had surrendered, but Japan had not. American forces had fought costly battles at Iwo Jima and Okinawa, and military planners were preparing for a possible invasion of the Japanese home islands. No one could know precisely how many lives such an invasion would cost, but we expected bitter resistance. My responsibility was to end the war as quickly as possible while considering the lives of American servicemen and the consequences of every available course of action.

A Weapon Unlike Any Other

On July 16, 1945, while I was attending the Potsdam Conference, the first atomic device was successfully tested in New Mexico. The message I received told me that the experiment had succeeded beyond expectations. We now possessed a weapon capable of destroying much of a city with a single bomb. The Allies issued the Potsdam Declaration calling upon Japan to surrender or face "prompt and utter destruction." Japan did not immediately accept those terms.

Hiroshima

On August 6, 1945, an American B-29 dropped the atomic bomb Little Boy on Hiroshima. The city contained important military facilities and troops, but it was also filled with civilians. The destruction was immense. I announced to the American people that an atomic bomb had been used and warned Japan that further attacks could follow if its leaders refused to surrender. From Washington, the objective seemed clear: force an end to a war that had already consumed millions of lives.

Nagasaki and Soviet Entry

Japan still had not surrendered when the Soviet Union declared war on Japan and attacked Japanese forces in Manchuria. On August 9, another American atomic bomb, Fat Man, was dropped on Nagasaki after the mission could not attack its primary target, Kokura. Japan's leaders now faced atomic destruction, Soviet intervention, conventional bombing, blockade, and the possibility of invasion. Emperor Hirohito intervened in the divided Japanese government, and Japan announced its acceptance of surrender on August 15.

The War Ends

On September 2, 1945, representatives of Japan formally surrendered aboard the USS Missouri in Tokyo Bay. World War II was over. My presidency, however, was only beginning. I soon faced an expanding confrontation with the Soviet Union, the reconstruction of Europe, the creation of NATO, recognition of Israel, the Berlin Airlift, and eventually the Korean War. At home, I ordered the desegregation of the armed forces and fought a difficult election campaign in 1948 that nearly everyone expected me to lose. I won.

Truman Learns About the Bomb and the War Approaches - Told by Truman

On April 12, 1945, I was summoned to the White House. Eleanor Roosevelt met me and told me that President Franklin Roosevelt was dead. I asked whether there was anything I could do for her. She answered, "Is there anything we can do for you? For you are the one in trouble now." She understood immediately what had happened. After only eighty-two days as vice president, I had become President of the United States while the largest war in history was still being fought.

A Secret Roosevelt Had Barely Shared

The next day, Secretary of War Henry Stimson began telling me about an immense secret undertaking. Soon I learned more from General Leslie Groves and others. The United States was attempting to construct an atomic bomb. I had known almost nothing about the Manhattan Project as vice president, despite the tremendous resources devoted to it.

Now the responsibility for what happened next belonged to my administration. I did not yet know whether the weapon would work. But I understood what I was being told: if successful, this bomb might possess destructive power unlike any weapon previously used.

Iwo Jima Shows the Price of Victory

The Pacific War gave me little reason to expect Japan's defeat would come easily. The Battle of Iwo Jima had ended only weeks before I became president. Nearly 7,000 Americans were killed and roughly 20,000 wounded during the fighting. Almost all of the approximately 21,000 Japanese defenders were killed or captured, with relatively few surviving as prisoners.

Those figures mattered. Japan's forces had demonstrated that they could defend small islands with extraordinary determination. Our soldiers and Marines were advancing toward the Japanese home islands, and each step seemed to become more costly.

Okinawa Becomes a Warning

Then came Okinawa. The battle lasted from April into June 1945 and became one of the bloodiest campaigns of the Pacific War. American forces suffered more than 12,000 dead, with tens of thousands more wounded or otherwise counted among casualties. Japanese military deaths were vastly higher, and enormous numbers of Okinawan civilians also died. Kamikaze attacks struck American ships repeatedly.

If Okinawa was a preview of fighting on the Japanese home islands, an invasion could be terrible. Our military was therefore preparing Operation Downfall, the planned invasion of Japan. Operation Olympic would attack Kyushu in late 1945, followed by Operation Coronet against the Tokyo region in 1946 if necessary. Casualty estimates varied greatly, and later claims about exact numbers became controversial, but nobody advising me expected an invasion to be cheap.

What Was Japan Thinking?

Japan's leaders also knew their situation was deteriorating. American submarines and aircraft had devastated shipping. Cities were being destroyed by conventional bombing. Food and fuel were increasingly scarce. Yet the Japanese government remained divided over surrender.

Some officials hoped the Soviet Union, which had not yet entered the Pacific War against Japan, might help mediate an end to the conflict. Japan sent diplomatic messages exploring Soviet mediation. But its leaders had not agreed to accept the Allied demand for surrender, and powerful military figures still hoped that inflicting enormous casualties during an American invasion might produce more favorable terms.

The Americans could read many Japanese diplomatic communications through intercepted and decoded messages. We therefore knew that peace maneuvering existed, but we also knew that Japan's government had not yet accepted our terms.

A Message from New Mexico

In July, I traveled to Potsdam, outside Berlin, to meet Winston Churchill and Joseph Stalin. Germany had surrendered, but Europe was devastated and difficult questions about the postwar world were already emerging. Then, on July 16, scientists in New Mexico tested the first atomic device.

The message reaching us was deliberately guarded, but its meaning became clear: the experiment had succeeded spectacularly. The weapon worked. I now possessed another possible means of ending the war.

At Potsdam, I also spoke with Stalin about Soviet entry into the war against Japan. The Soviet Union had previously agreed to enter the Pacific conflict after Germany's defeat, and Stalin indicated that the Soviets intended to fulfill that commitment.

The Potsdam Declaration

On July 26, 1945, the United States, Britain, and China issued the Potsdam Declaration. We called upon Japan to surrender and warned that refusal would result in "prompt and utter destruction." The declaration promised that Japan would not be destroyed as a nation, but militarism would be eliminated, occupied territories would be taken away, war criminals would face justice, and Allied forces would occupy Japan until peaceful government was established.

The declaration did not explicitly guarantee the future position of Emperor Hirohito. That issue mattered greatly inside Japan and remained one of the complications surrounding surrender. Japan did not accept the declaration.

The Decision Moves Closer

By the end of July, several paths were converging. We could continue conventional bombing and blockade. We could await Soviet entry into the war. We could invade Japan. We could attempt to use the atomic bomb, whose power had now been demonstrated at Trinity. These possibilities were not considered in complete isolation from one another; military planning continued on several tracks simultaneously.

Where Would the Atomic Bomb Be Used? (Summer 1945) - Told by Groves

By the spring of 1945, the Manhattan Project was approaching the point when our work might become an operational weapon. My responsibility was no longer limited to building the bomb. The Army also had to determine how it could be used if the President authorized it. That meant confronting a grim question: if we had only a small number of atomic bombs, where would we drop them?

The Target Committee Meets

Beginning in April 1945, a Target Committee composed of military officers and scientists met to examine possible Japanese targets. Among the cities considered during the process were Hiroshima, Kyoto, Kokura, and Niigata. The committee examined military and industrial importance, geography, city size, surrounding terrain, and the likelihood that bombing conditions would allow the weapon's effects to be observed.

This was not simply a search for the largest city. Tokyo had already suffered catastrophic destruction from conventional incendiary bombing, particularly the March 9–10 raid. For the atomic bomb, planners wanted a target where the effects of this new weapon could be clearly measured. That meant cities that had not already been heavily destroyed could receive greater consideration.

Why Hiroshima Rose to the Top

Hiroshima possessed several characteristics that attracted military planners. It was an important military center containing the headquarters of Japan's Second General Army and other military facilities. It was also a transportation and communications center connected to Japan's war effort.

Its physical characteristics mattered as well. Hiroshima was a substantial urban area surrounded partly by terrain that planners believed could influence the blast. Much of the city remained relatively undamaged by previous bombing. If an atomic bomb exploded there, its destructive effects could be assessed more clearly than in a city already covered in ruins.

But Hiroshima was not merely a military installation. It was a living city filled with civilians. That fact was understood.

Kyoto Creates a Battle Inside Washington

Kyoto became one of the most controversial proposed targets. Militarily and industrially, planners considered it significant, and its large urban area made it suitable for assessing the bomb's effects. I believed there were reasons for keeping it on the target list.

Secretary of War Henry Stimson strongly disagreed. Kyoto had been Japan's imperial capital for centuries and remained one of the nation's most important cultural and religious centers. Stimson feared that destroying it would create enormous bitterness among the Japanese people and damage America's ability to build a peaceful relationship with Japan after the war.

The disagreement continued through the spring and summer. Stimson repeatedly pressed his case at the highest levels of government. Ultimately, Kyoto was removed from the atomic target list.

Kokura and Niigata

Kokura was another important possibility because it contained the Kokura Arsenal, a significant military-industrial complex. Niigata was considered because of its industrial facilities and port. Target lists changed as planners evaluated operational conditions and as Kyoto was removed.

The final operational planning placed Hiroshima, Kokura, Niigata, and Nagasaki among the designated targets, although weather and other conditions would determine what happened during an actual mission. The bomb crews needed alternate targets because cloud cover could make visual bombing impossible.

That contingency would later become enormously important. On August 9, Kokura was the primary target of the second atomic-bomb mission. Clouds and smoke obscured the aiming point, and the aircraft eventually proceeded to its secondary target: Nagasaki.

Why Leave Potential Targets Undamaged?

One of the most uncomfortable aspects of the planning was the desire to understand what the new bomb could actually do. Certain potential atomic targets were therefore protected from ordinary bombing attacks so that, if struck by an atomic bomb, the damage could be more clearly evaluated.

To military planners, this provided information about a weapon whose effects were still uncertain. To later generations, it raises an obvious ethical problem. A city was simultaneously a military target, a scientific opportunity to measure destruction, and the home of tens or hundreds of thousands of human beings. Those realities existed together.

My Name is Tsutomu Yamaguchi: Survivor of Hiroshima and Nagasaki

I was born in Nagasaki, Japan, in 1916. I became an engineer and worked for Mitsubishi Heavy Industries, designing oil tankers during a time when Japan was at war across Asia and the Pacific. By 1945, our country had been battered by bombing, shortages, and years of conflict. I had a wife and young son in Nagasaki, and more than anything, I wanted to return safely to them.

A Business Trip to Hiroshima

In the summer of 1945, my work took me to Hiroshima for several months. On August 6, my assignment was nearly finished. I was preparing to leave the city when I realized I had forgotten an important personal item and turned back. It was shortly after eight in the morning when I noticed an American aircraft high above. Then I saw something descending from it. Suddenly, there was an extraordinary flash in the sky.

The Sun Fell Upon Hiroshima

The light was unlike anything I had ever seen. I was thrown by the force of the explosion, my body badly burned and my eardrums injured. When I regained awareness, the familiar city around me had become almost unrecognizable. Buildings were broken apart. Fires spread through the ruins. Injured people wandered through smoke and darkness. I did not yet understand what weapon had struck us. I knew only that Hiroshima had been transformed in an instant.

Escaping a Destroyed City

I spent that night in an air-raid shelter. Despite my injuries, I was determined to return home. The next day, I searched for a way out of Hiroshima and eventually boarded a train. That a train could still carry survivors away from such destruction seemed almost impossible. I traveled toward Nagasaki burned, bandaged, exhausted, and carrying memories that I could scarcely explain.

Home in Nagasaki

When I reached my family, even my wife initially had difficulty recognizing me because of my burns and bandages. Yet I had survived, and I believed the worst was behind me. On August 9, only three days after Hiroshima, I reported to my workplace. I tried to explain to my supervisor that a single bomb had destroyed almost an entire city. The idea sounded unbelievable. How could one weapon possess such power?

The Flash Came Again

While I was describing Hiroshima, another brilliant flash filled the sky. Nagasaki had been struck by a second atomic bomb. Once again came the blast, shattered glass, collapsing structures, smoke, and destruction. I had survived Hiroshima only to experience the same terrible weapon again in my own city. My wife and child also survived. Later I learned that my wife had gone out searching for medicine for my burns; circumstances surrounding that journey helped place her and our son where they could survive the explosion.

Living After the Bombs

Survival did not mean that the danger had ended. I suffered from burns, fever, illness, and other effects associated with radiation exposure. Like many survivors, I carried physical and emotional consequences for years. I returned to work and eventually lived a long life, but Hiroshima and Nagasaki never truly disappeared from my thoughts. They remained with me in memories of ruined streets, injured people, and the terrible light that arrived without warning.

Hiroshima and Nagasaki: Aug 6 &Aug 9, 1945 - Told by Truman and Yamaguchi

Harry S. Truman: By August 1945, I faced a Japan that had been badly weakened but had not surrendered. American forces had suffered heavily at Iwo Jima and Okinawa, conventional bombing had devastated Japanese cities, a naval blockade was tightening, and plans for an invasion of the home islands continued. The atomic bomb offered another possibility: strike Japan with such overwhelming force that its leaders would accept surrender before an invasion became necessary. No president before me had possessed such a weapon. Now I had to govern in a world where one existed.

August 6: Hiroshima

Harry S. Truman: Early on August 6, the B-29 Enola Gay approached Hiroshima carrying the uranium bomb called Little Boy. Hiroshima was an important military headquarters and communications center, but it was also a city filled with civilians. At approximately 8:15 in the morning, the bomb was released and exploded above the city. A single aircraft had delivered a weapon with an explosive yield of roughly 15 kilotons of TNT. Much of Hiroshima was devastated.

Tsutomu Yamaguchi: I was there. I had been in Hiroshima on business for Mitsubishi Heavy Industries and was preparing to return home to Nagasaki. That morning, I saw an American aircraft high in the sky. Then came an intense flash. I instinctively threw myself toward the ground before the blast struck. The force hurled me through the air. My face and arm were badly burned, my hearing was damaged, and when I could understand my surroundings again, the city I had known had become something almost beyond recognition.

A City of Fire

Tsutomu Yamaguchi: Smoke rose everywhere. Buildings had collapsed or burned. Injured people moved through the ruins searching for water, medical treatment, and relatives. I made my way toward an air-raid shelter and eventually found coworkers who had also survived. Hospitals and aid stations faced numbers of casualties no city could have prepared to treat. Doctors and nurses were themselves among the dead and injured.

Many survivors did not yet understand another danger. People who appeared to have escaped the worst burns later developed fever, weakness, bleeding, hair loss, and other illnesses associated with radiation exposure. In those first hours, however, we did not have the knowledge or language to explain what was happening.

Washington Announces a New Weapon

Harry S. Truman: Later that day, I announced that the United States had used an atomic bomb. I described Hiroshima as an important Japanese military base and warned Japan that continued refusal to surrender could bring further destruction. From the American government's perspective, the purpose was to shock Japan's leadership into ending the war.

But the bomb did not immediately produce a surrender. Japan's leadership remained divided. Some leaders sought a way to end the conflict while important military figures resisted accepting the Allied terms. Meanwhile, events were moving quickly beyond Hiroshima.

The Soviet Union Enters the War

Harry S. Truman: Late on August 8 by European time, the Soviet Union declared war on Japan, and Soviet forces launched a massive offensive against Japanese forces in Manchuria beginning August 9 local time. Japan had hoped Moscow might help mediate an end to the war. That possibility disappeared.

Japan was now confronting several crises at once: Hiroshima had been destroyed by an unknown new weapon, the Soviet Union had entered the war, American conventional attacks continued, and another atomic bomb was ready.

August 9: The Bomb Comes Again

Tsutomu Yamaguchi: Somehow, I escaped Hiroshima. Despite my burns and bandages, I traveled by train back to Nagasaki. On August 9, I reported to Mitsubishi and tried to explain to my supervisor what had happened. I told him that one bomb had destroyed Hiroshima. The claim seemed almost impossible. Then, at approximately 11:02 that morning, the room was filled with another brilliant flash.

The plutonium bomb called Fat Man had exploded over Nagasaki.

Kokura had been the mission's primary target, but clouds and smoke interfered with the bombing run. The aircraft continued to Nagasaki. Once again I found myself beneath an atomic attack, only three days after surviving Hiroshima.

Nagasaki Burns

Tsutomu Yamaguchi: Nagasaki's hills limited some of the blast compared with Hiroshima, but the destruction around the explosion was still enormous. Buildings disappeared. Fires spread. Tens of thousands of people were killed, many immediately and others from their injuries and radiation effects.

My wife and infant son survived as well. I later learned that my wife had been away from our home obtaining ointment for my burns when the bomb exploded. The injuries I carried from Hiroshima had indirectly affected where she was when Nagasaki was struck.

I had survived the atomic bomb twice. At the time, survival did not feel like a historical distinction. It meant finding my family and trying to remain alive.

Two Views of the Same Days

Harry S. Truman: From Washington, we saw military maps, intelligence reports, casualty estimates, invasion plans, and a Japanese government that had still not surrendered. I believed the atomic bombs could help bring the war to a rapid conclusion and prevent the terrible casualties expected from continued fighting and invasion.

Tsutomu Yamaguchi: From the ground, there were no maps. There were people. There were burned bodies, destroyed homes, desperate families, overwhelmed medical workers, and survivors who could not understand why people who had escaped the explosion were becoming sick. Both perspectives belong to the history.

On August 6 and August 9, 1945, humanity learned that a single aircraft carrying a single weapon could devastate a city. Within days, Japan would surrender. But the debate over why Japan surrendered, whether both atomic bombings were necessary, what alternatives existed, and how those decisions should be judged would continue long after the fires of Hiroshima and Nagasaki had gone out.

Japan Surrenders: The Bombs, Soviet Intervention, and the Emperor's Decision (August–September 1945) - Told by Harry S. Truman

By August 1945, I knew Japan was losing the war, but losing a war and agreeing to surrender are not the same thing. American submarines had devastated Japanese shipping. Our aircraft were destroying cities and industries. Japan faced severe shortages of fuel and other resources, while our forces prepared for a possible invasion of the home islands. Then, within a few extraordinary days, three shocks struck Japan's leaders: Hiroshima was destroyed by an atomic bomb, the Soviet Union entered the war, and Nagasaki was struck by a second atomic bomb. To understand Japan's surrender, you must understand all of them.

Hiroshima Changes the War

On August 6, the uranium bomb Little Boy exploded over Hiroshima. Japan's leaders received reports describing destruction unlike anything previously caused by a single aircraft. We announced publicly that the weapon was an atomic bomb and warned that additional destruction would follow if Japan continued fighting.

Yet there was no immediate surrender. Japan's Supreme Council for the Direction of the War remained divided. Some leaders understood that the situation was becoming hopeless, while military hardliners resisted surrender on the terms offered by the Allies. Japan still had large forces and was preparing to make an American invasion enormously costly.

The Soviet Door Slams Shut

Japan had also been quietly seeking Soviet assistance in obtaining a negotiated end to the war. That strategy depended upon the Soviet Union remaining neutral in the Pacific conflict. It did not.

On August 8, the Soviet Union declared war on Japan. Beginning on August 9 in Asia, Soviet forces launched a massive offensive against Japan's Kwantung Army in Manchuria. Soviet troops also moved against Japanese positions elsewhere in northeast Asia and later into territories such as southern Sakhalin and the Kuril Islands.

For Japan, Soviet entry created a strategic disaster. The government could no longer hope Moscow might serve as an intermediary with the Allies. Japan now faced powerful enemies attacking from both east and west.

Then Came Nagasaki

On August 9, while Japan's leaders struggled with the Soviet attack and the destruction of Hiroshima, another atomic bomb was used. The plutonium weapon Fat Man exploded over Nagasaki after the American bomber had been unable to attack its primary target, Kokura.

The combination was staggering. Within approximately three days, two Japanese cities had suffered atomic attacks, and the Soviet Union had entered the war. Japan's military situation had been deteriorating for months, but suddenly the country's leaders had to consider the possibility that additional cities could be destroyed while Soviet armies advanced across Japanese-held territory. Still, Japan's leadership could not agree.

Six Men Divided Three Against Three

The key Japanese council was effectively deadlocked. Some officials favored accepting the Potsdam terms if the imperial institution could be preserved. Others wanted additional conditions, including restrictions concerning occupation, disarmament, and war-crimes proceedings.

The division became so serious that Emperor Hirohito took the unusual step of personally intervening. During an imperial conference in the early hours of August 10, he supported ending the war. Japan communicated that it was prepared to accept the Potsdam Declaration provided the emperor's sovereign position was not prejudiced.

Our reply did not provide the unconditional guarantee some Japanese leaders wanted. We stated that the emperor's authority would be subject to the Supreme Commander for the Allied Powers and that Japan's ultimate form of government would be established according to the freely expressed will of the Japanese people.

The Emperor Decides Again

Even after receiving the Allied response, disagreement continued inside Japan. On August 14, Emperor Hirohito again intervened in favor of accepting surrender.

That did not mean everyone was willing to obey. During the night of August 14–15, a group of Japanese officers attempted a coup. They sought to prevent the emperor's recorded surrender message from being broadcast and hoped to continue the war. The attempt failed.

At noon on August 15 in Japan, the emperor's recorded voice was broadcast to his people. Most Japanese citizens had never heard their emperor speak before. Using formal language, Hirohito announced that Japan would accept the Allied terms. He referred to the enemy's use of a "new and most cruel bomb," while also describing the broader war situation as having developed unfavorably. The fighting was coming to an end.

Why Did Japan Surrender?

People have argued ever since about which event finally broke Japan's resistance. The atomic bombs were enormously important. Soviet intervention was also a devastating strategic and diplomatic blow. Conventional bombing, blockade, shortages, military defeats, and fear of invasion had already weakened Japan severely. Internal disagreements delayed the decision until the emperor intervened.

History becomes misleading when we force all of this into one simple explanation.

From my position as President, I believed the atomic bombs helped bring the war to a rapid conclusion. From Tokyo, however, Japanese leaders were confronting several disasters simultaneously. Hiroshima, Soviet intervention, Nagasaki, military collapse, blockade, and the emperor's decision all belonged to those final days.

The War Finally Ends

On September 2, 1945, representatives of Japan boarded the USS Missouri in Tokyo Bay. General Douglas MacArthur presided over the ceremony while representatives of the Allied powers watched. Japanese Foreign Minister Mamoru Shigemitsu signed on behalf of the Japanese government, and General Yoshijiro Umezu signed for the Imperial General Headquarters. The Second World War was formally over.

The Atomic Age Begins: Survivors, Occupation, Nuclear Weapons, and the Debate That Never Ended (1945–Beyond) - Told by Tsutomu Yamaguchi

I survived Hiroshima on August 6, 1945, returned home to Nagasaki, and survived another atomic bomb three days later. When Japan announced its surrender, the war was ending, but for those of us who had been beneath the bombs, August 1945 was not an ending. We were only beginning to understand what had happened to our bodies, our cities, and our world. The explosions lasted seconds. Their consequences would continue for generations.

The Mysterious Sickness

In the days and weeks after the bombings, survivors suffered illnesses that were initially difficult for many people to understand. Some who had escaped the immediate blast developed fever, weakness, bleeding, hair loss, infections, and other symptoms. Doctors gradually confronted the effects of radiation exposure in addition to burns, trauma, and malnutrition. I suffered severe burns and later became dangerously ill.

Those exposed to the atomic bombings became known as hibakusha, meaning explosion-affected people. Survival itself could bring new hardships. Some hibakusha later experienced increased risks of leukemia and certain cancers, while many also faced discrimination because others incorrectly feared radiation sickness might be contagious or hereditary.

Cities Rise from the Ruins

Hiroshima and Nagasaki had lost enormous numbers of people. By the end of 1945, estimates commonly place Hiroshima's deaths at around 140,000 and Nagasaki's at around 70,000, although exact totals remain uncertain. Those numbers include people killed immediately and others who died during the following months.

Yet people returned. Streets were cleared. Homes, schools, hospitals, businesses, and transportation systems were rebuilt. Hiroshima eventually became internationally associated with peace and nuclear disarmament. Nagasaki rebuilt as well, while preserving reminders of what had occurred. The cities refused to remain only monuments to destruction. They became living communities again.

Japan Under Occupation

After surrender, Japan entered an entirely different period. Allied occupation forces arrived under General Douglas MacArthur as Supreme Commander for the Allied Powers. Japan was disarmed and demilitarized, war-crimes trials were conducted, political institutions were reformed, and a new constitution took effect in 1947. Its Article 9 renounced war as a sovereign right of the nation and rejected maintaining war potential, though Japan later developed Self-Defense Forces.

Our country also had to confront the destruction caused by years of warfare. Japan itself had suffered terribly in 1945, but Japanese forces had also inflicted enormous suffering throughout China, Korea, Southeast Asia, the Pacific, and elsewhere. Rebuilding Japan could not erase that wider history.

The Secret Does Not Remain American

Anyone who imagined the United States would permanently possess the atomic bomb alone was soon proven wrong. In August 1949, the Soviet Union successfully tested its first atomic device. The American nuclear monopoly had lasted only four years.

Then the weapons became vastly more powerful. The United States tested its first full-scale thermonuclear device in 1952, and the Soviet Union developed thermonuclear weapons as well. Britain, France, China, and eventually other nations acquired nuclear arsenals. Bombs thousands of times more powerful than the explosive weapons of earlier wars became part of international strategy.

Hiroshima and Nagasaki were no longer merely Japanese memories. They were warnings about what another world war might become.

Could the Bombings Have Been Avoided?

Historians have debated the decision ever since. President Truman and many American officials argued that using the bombs helped end the war rapidly and avoided an invasion of Japan that could have produced enormous American and Japanese casualties. Supporters of the decision also point to Japan's fierce resistance, demonstrated at battles such as Iwo Jima and Okinawa, and the unwillingness of important Japanese military leaders to surrender even in August 1945.

Other historians have asked whether Japan might have surrendered without two atomic attacks. They examine Soviet entry into the war, Japan's attempts to seek Soviet mediation, the possibility of modifying surrender terms concerning the emperor, continued blockade and conventional bombing, or demonstrating the atomic bomb away from a populated city. Historians continue to disagree about how practical or effective these alternatives would have been.

The debate is not settled by pretending the evidence points in only one direction.

My Life After Two Bombs

For many years, I did not make my experiences the center of my public life. I returned to work, raised my family, and lived with the physical and emotional consequences of what I had witnessed. Later, I began speaking more openly about nuclear weapons. In 2009, the Japanese government officially recognized me as a survivor of both Hiroshima and Nagasaki.

I spoke before the United Nations in 2006 and called for the abolition of nuclear weapons. I had no theory to offer more powerful than experience. I knew what an atomic bomb did because I had stood beneath one twice.