The Manhattan Project

The Birth of the Atomic Bomb in the Words of Its Creators, Eyewitnesses, and Historians


Edited by Cynthia C. Kelly

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On the seventy-fifth anniversary of the first atomic bomb, discover new reflections on the Manhattan Project from President Barack Obama, hibakusha (survivors), and the modern-day mayors of Hiroshima and Nagasaki.

The creation of the atomic bomb during World War II, codenamed the Manhattan Project, was one of the most significant and clandestine scientific undertakings of the 20th century. It forever changed the nature of war and cast a shadow over civilization. Born out of a small research program that began in 1939, the Manhattan Project would eventually employ nearly 600,000 people and cost about $2 billon ($28.5 billion in 2020) — all while operating under a shroud of complete secrecy.

On the 75th anniversary of this profoundly crucial moment in history, this newest edition of The Manhattan Project is updated with writings and reflections from the past decade and a half. This groundbreaking collection of essays, articles, documents, and excerpts from histories, biographies, plays, novels, letters, and oral histories remains the most comprehensive collection of primary source material of the atomic bomb.



The Manhattan Project Seventy-Five Years Later

When future generations look back on the twentieth century, few events will rival the harnessing of nuclear energy as a turning point in world history. The 75th anniversary of the Manhattan Project is an opportune occasion to reflect upon the top-secret effort that enabled the Allies to end World War II, but also introduced a major new force in human affairs. As early as 1944, Danish physicist Niels Bohr predicted that atomic weapons could become “a perpetual menace to society.”

This edition of The Manhattan Project adds a section drawn from interviews taken since 2007. In these, Manhattan Project veterans share diverse reflections on the use of the atomic bombs, and Hiroshima and Nagasaki survivors recount their experiences. Also included are the opinions of former United States and Soviet leaders. In the words of Mikhail Gorbachev, the world is “sitting on a nuclear powder keg.”

This new preface traces the efforts to preserve the places and significant properties of the Manhattan Project. Having authentic first-of-a-kind facilities, equipment, and other artifacts is essential to preserving this complex history. As Richard Rhodes, Pulitzer Prize–winning author of The Making of the Atomic Bomb, has said, “When we lose parts of our physical past, we lose parts of our common social past as well.” The following tells the story of how critical Manhattan Project properties were salvaged and a national historical park created.

Twenty-five years ago, 50 wooden structures where the world’s first atomic bombs were designed stood deep inside the Los Alamos National Laboratory’s property. The buildings were abandoned in the 1950s and few people even knew they existed.

In 1997, colleagues in the Department of Energy (DOE) alerted me that all of the remaining Manhattan Project properties owned by the laboratory were slated for demolition. While the laboratory was required to mitigate the loss with documents and photographs, preservation was not considered an option.

Given their historic significance, the Advisory Council on Historic Preservation agreed to investigate. On November 5, 1998, Council members visiting Los Alamos were struck by the simplicity of the one-story wooden structures located on the “V-Site” where the atomic age was born. As architect Bruce D. Judd commented, the humble V-Site properties were “monumental in their lack of monumentality.” However, laboratory officials explained that Congress appropriated funds to demolish, not restore, them. Without other funds, the properties were doomed.

Fortunately, the White House Millennial Project had convinced Congress to provide $30 million to preserve Federal properties significant to America’s history that were in danger of being lost. After a government-wide competition, two Save America’s Treasures grants were awarded for DOE properties in 1999: $700,000 for the V-Site properties at Los Alamos and $320,000 for the Experimental Breeder Reactor–I in Idaho.

The catch was that the grant funds had to be matched with non-Federal funds. Raising a million dollars became my next mission, prompting me to leave the government after twenty-five years. The first step was to launch the Atomic Heritage Foundation (AHF), a tax-exempt non-profit dedicated to preserving and interpreting the history of the Manhattan Project.

Richard Rhodes became AHF’s first board member. Rhodes opened doors to Senators Pete Domenici and Jeff Bingaman of New Mexico and drew enthusiastic crowds to AHF’s events. Eventually, AHF raised the necessary funds for the Save America’s Treasures projects. In 2006, the humble structures of the V-Site were restored and quickly became a touchstone for the Los Alamos National Laboratory.

The restoration of the properties at Los Alamos raised questions about what other Manhattan Project properties should be preserved. What about the B reactor at Hanford, Washington, which produced the first plutonium, or the K-25 plant at Oak Ridge, Tennessee, which produced enriched uranium? Tasked with producing a report for Congress, AHF convened a series of public meetings around the country in 2003. The meetings included federal, state and local officials, Manhattan Project veterans, historical societies, and members of the public. For the first time, the public discussed the possibility of establishing a national historical park for the Manhattan Project.

For over a decade, the Congressional delegations from New Mexico, Washington, and Tennessee were instrumental in the success of the legislation for a new park. In 2003, Senators Maria Cantwell of Washington and Jeff Bingaman of New Mexico introduced legislation requiring a “special resource study.” With bipartisan, bicameral support, Congress passed the legislation in September 2004. Despite an official policy of “no new parks,” President George W. Bush signed it.

In 2011, the long-awaited study from the National Park Service (NPS) recommended creating a Manhattan Project National Historical Park with units at Los Alamos, Oak Ridge, and Hanford. For the next three years, AHF led a broad national coalition with representatives from the Manhattan Project communities, the National Parks Conservation Association, and the National Trust for Historic Preservation.

Congressman Doc Hastings, who represented Hanford, was an important champion for the legislation in the House. However, an initial attempt at passage failed in 2012 as opponents raised fears that the park would simply celebrate nuclear weapons. Two years later, Hastings managed to tuck the bill inside the mammoth National Defense Authorization Act, which then passed Congress on December 12, 2014.

News of the legislation to create a Manhattan Project park unsettled officials in Hiroshima and Nagasaki, Japan, who feared that the National Park Service’s interpretation would not address the impact of the atomic bombs on Japan. In May 2015, AHF met with the Mayors of Hiroshima and Nagasaki in New York City to assure them that the Park Service intended to tell the whole story, including “what happened under the mushroom cloud.”

In November 2015, the park became official, a joint enterprise between the Department of Energy and the National Park Service. The Department of Energy would continue to own and maintain its Manhattan Project properties. As the nation’s storyteller, the Park Service would interpret the history for the public.

Just four years old, the park is a work in progress. Currently, public access to many of the Manhattan Project properties is restricted because of national security or safety issues. Funding constraints have made it difficult for the Park Service to launch the park expeditiously. However, NPS is making steady progress, working with local museums, historical societies, educators, and nonprofit organizations to engage visitors in learning about the “Secret Cities” and the dawn of the nuclear age.

The Atomic Heritage Foundation has focused on creating extensive online resources. AHF’s main website ( has hundreds of articles and primary source documents on the history of the Manhattan Project and its legacy. Profiles of 14,000 Manhattan Project veterans enable family members to research their relative’s role.

The “Voices of the Manhattan Project” website ( has over 600 oral histories, fully transcribed and searchable. The collection has dozens of fascinating recordings with top-echelon Manhattan Project leaders, including J. Robert Oppenheimer and General Leslie Groves, taken by Stephane Groueff in 1965. Another 80 interviews with a cross-section of Hanford employees were captured by S. L. Sanger in 1986. The collection has another 100 interviews recorded by Pulitzer Prize–winning historians Martin J. Sherwin and Richard Rhodes.

Finally, AHF has taken over 350 interviews from Nobel laureates, members of the Special Engineer Detachment, women scientists, African Americans, Native Americans, and downwinders. The “Voices of the Manhattan Project” site is a treasure trove for journalists, scholars, TV and radio producers, museums, students, and the public.

AHF’s “Ranger in Your Pocket” website ( provides access to hundreds of short, two- to five-minute audio/visual programs. Each program addresses an aspect of work or daily life using first-hand accounts. Visitors can access these programs on their smartphones and tablets as they walk down Bathtub Row at Los Alamos or tour the B Reactor at Hanford, for example. These resources have also been widely used by teachers in classrooms and by museums.

Section Ten of this new edition of The Manhattan Project features selections from AHF’s oral history collection. Readers can see the full transcripts and listen to or watch the interviews online. Manhattan Project veterans share their personal reflections on the decision to drop the atomic bombs. Survivors from Hiroshima and Nagasaki describe the horrific devastation and their lifelong suffering. As Mayor Taue of Nagasaki explains, “The atomic bomb survivors’ first and foremost wish is that no one in this world will ever experience what they have gone through.”

The Manhattan Project’s legacy continues as we navigate the perils of nuclear weapons in the twenty-first century. Former U.S. government officials George Shultz, William S. Perry and Sam Nunn warn that the threat of nuclear war is still with us seventy-five years later. Beatrice Finn, who received the 2017 Nobel Peace Prize, calls on nations to choose “the end of nuclear weapons over the end of us!”

Please enjoy the diverse, thought-provoking contributions in this seventy-fifth anniversary edition of The Manhattan Project.

Preserving the Manhattan Project

Cynthia C. Kelly

President, Atomic Heritage Foundation

Decades before the Manhattan Project unleashed the world’s first atomic bomb, the possibility of harnessing the enormous energy inside an atom captured the imaginations of scientists. On September 12, 1933, while crossing the street in London, Hungarian physicist Leo Szilard realized the possibility of a nuclear chain reaction. Five years later, on December 21, 1938, two German scientists split the uranium atom. Word spread quickly as physicists from Britain, France, Italy, Russia, and the United States rushed to duplicate the experiment. The race to develop an atomic bomb had begun.

This book chronicles the top-secret Manhattan Project, the U.S. effort to develop, test, and use an atomic bomb in World War II, and the enduring legacy it has left. The story is told through first-hand accounts, oral histories, and contemporary documents, as well as commentary by leading historians and political leaders.

Albert Einstein’s letter of August 2, 1939 warned President Franklin D. Roosevelt that Germany may have an atomic weapon program. In March 1941, British scientists urged Americans to develop such a weapon “with the highest priority.” Still more time elapsed as the American effort slowly materialized. It was not until September 1942 that hard-driving General Leslie R. Groves took charge, wasting no time to select personnel, production sites and set ambitious schedules to produce an atomic bomb.

Why did the Manhattan Project succeed despite long odds? The Army Corps of Engineers’ dynamo General Groves and scientific director J. Robert Oppenheimer, scientific director of the laboratory at Los Alamos, New Mexico, were a formidable pair. With Roosevelt’s backing, Groves enlisted America’s leading industrial firms to construct and operate the vast facilities needed to produce the ingredients for the bomb. Oppenheimer recruited a “galaxy of luminaries,” Nobel laureates and promising young physicists, engineers, and other scientists, many of them refugees from Nazi-dominated Europe.

Over 125,000 people, most in their twenties and thirties, worked on the top-secret Manhattan Project. Through a variety of selections, the book portrays life in the Manhattan Project with its youthful exuberance and unrelenting intensity. From university professors to high school girls, members of the newly created Special Engineer Detachment to construction laborers of all sorts, people worked around the clock, living in “alphabet” houses, makeshift construction camps, barracks, and trailers.

General Groves was, among other things, the architect of an intelligence revolution that took security measures to unprecedented heights. Because of strict security procedures, the vast majority of Manhattan Project employees only learned what they had been working on after the first bomb was dropped on August 6, 1945. However, as comprehensive as the security measures were, they were not totally effective as several spies infiltrated the project. Soviet scientists and leaders working on their atomic bomb took advantage of the information that the espionage provided.

Concerned scientists debated among themselves the moral and ethical implications of using an atomic bomb. In June and July 1945, over 150 scientists signed petitions to the Secretary of War Henry Stimson and to President Harry Truman recommending against its unannounced military use against Japan. While these recommendations did not prevail, many scientists accurately predicted a nuclear weapons arms race and formulated proposals for international controls to try to prevent it.

On the morning of August 6, 1945, the first atomic bomb, Little Boy, was dropped from the B-29 bomber, the Enola Gay, over Hiroshima. Statements by President Truman and Secretary of War Stimson initiated an avalanche of radio announcements and newspaper articles in the United States and around the world. The American public was relieved that the long and costly war was over and initially supported the decision to drop the bomb by an overwhelming majority of 85 percent.

As news about the full effects of the atomic bomb on Hiroshima and Nagasaki gradually reached the American public, support began to wane. A year after the bombings, John Hersey gave an immediacy to the human toll and destruction of Hiroshima in an influential article in The New Yorker. As the Cold War arms race increased the possibility of a nuclear holocaust, world leaders struggled to establish controls to prevent disaster. The problem and the debate continue today as illustrated by recent statements by former U.S. government officials and former Soviet Union President Mikhail Gorbachev.

The Atomic Heritage Foundation is a nonprofit organization dedicated to preserving the history of the Manhattan Project and its legacy through publications, oral histories, documentary films and the physical properties of the Manhattan Project. While most of the Manhattan Project properties have been lost, a handful of important properties remain at each major site.

In 2004, under bipartisan leadership, Congress provided an opportunity to reassess the fate of these remaining properties. The National Park Service is studying whether to create national Manhattan Project Historical Park sites at Los Alamos, New Mexico; Hanford, Washington; and Oak Ridge, Tennessee; and other significant sites.

Collaborative efforts with both public and private partners have saved several of the threatened properties. At Los Alamos, a Save America’s Treasures grant matched with non-federal funds provided the means to restore the humble “V-Site” properties where the Trinity test bomb was assembled and the modest cottage where J. Robert Oppenheimer and his family lived. At Hanford, Congress provided funds to restore the B Reactor and the M. J. Murdock Charitable Trust awarded the Atomic Heritage Foundation a grant for multimedia interpretative exhibits. At Oak Ridge, the Atomic Heritage Foundation, Partnership for K-25 Preservation and other state and local partners are working to preserve the north end of the mile-long K-25 gaseous diffusion plant, previously slated for demolition.

Over the next decade, you may be able to visit one or more national historical park sites for the Manhattan Project and tour some of the once top-secret facilities that changed the course of world history. Meanwhile, please visit our website at and immerse yourself in The Manhattan Project.

Cynthia C. Kelly

President, Atomic Heritage Foundation

A Great Work of Human Collaboration

By Richard Rhodes

No other story resonates quite like the story of the Manhattan Project. When I wrote my history The Making of the Atomic Bomb, I thought of it as the tragic epic of the twentieth century: Humankind invents the means of its own destruction. But the discovery of how to release the enormous energies latent in the nuclei of atoms has led to a world where world-scale war is no longer possible. Is that tragedy, or cause for celebration?

Nuclear power came out of the Manhattan Project as well, the first major source of energy not derived directly or indirectly from sunlight. I suppose there are those who would consider that development a tragedy, but as energy transitions go, it’s been orders of magnitude cleaner and safer than its predecessors, coal and oil, and now nuclear power appears poised to contribute to slowing global warming.

Yet neither of these outcomes was intentional. A few scientists suspected they might follow. Most of the military and civilian leaders who knew of the secret program to develop atomic bombs, from President Franklin D. Roosevelt and Prime Minister Winston Churchill on down, had more immediate concerns. Their desperate purpose, for which they were prepared to spend billions of dollars and divert precious materials and manpower from the immediate war effort, was to master the military technology of nuclear fission before Nazi Germany—as evil an empire as ever laid claim to the earth—succeeded in doing so. As it turned out, of course, Germany had hardly begun a bomb research program, and once the Soviet Union mastered the technology, after 1949, the new weapons proved unusable. Maybe the proper genre for the Manhattan Project story is irony, not tragedy.

Either way, it was epic in scope, in numbers of people and scale of investment and construction; epic as well in its daring transfer of physical and chemical processes directly from the laboratory to the huge enrichment and separation facilities at Oak Ridge, Tennessee, and Hanford, Washington. I can think of no other major new technical process that has been industrialized in so short a time—testimony to how dangerous the new weapons were understood to be, capable even of turning defeat into victory if it came to that.

Fortunately, it didn’t come to that. It came instead to a decision, more controversial now than it was in the summer of 1945, to use the first two bombs against Japanese cities in the hope of shocking the Japanese into surrender before the invasion of their home islands, scheduled for November, took an even greater toll of American and Japanese lives. That decision is discussed here by experts; I would only remind you that destroying Japanese cities with firebombing—destruction fully as total as the atomic bombings brought—had been underway for months, and that Hiroshima and Nagasaki would already have been burned out by August 1945 had they not been removed from the U.S. Air Force’s target list. The moral decision to use terror bombing against civilian populations had been made two years earlier, in Europe, and it was fully implemented in Japan in the last months of the war, until only cities with less than 50,000 population (excluding those on the atomic bombing target list) remained untouched.

These hard choices and decisions, following as they did from a great, and in the long run humane, work of human collaboration, are much of what gives the Manhattan Project story its almost mythic resonance. Harnessing the military technology of nuclear fission required genius, sacrifice and unremitting hard work, from digging ditches and hanging iron, to inventing new ways to detonate explosives, to figuring out how to remove a large strategic bomber from the immediate vicinity of a falling atomic bomb before the damned thing goes off.

Fewer and fewer of those who participated in the work remain alive to recall it to us face to face. To honor them and to preserve their memories, the Atomic Heritage Foundation, Cindy Kelly and her colleagues, have brought together here a rich sampling of their eyewitness accounts as well as of reconstructions by historians and even a fictional re-creation or two. I hope this memorial anthology revitalizes for you a time that was tragic, ironic and epic, all three, but most of all intensely human, and compelled from the beginning not by malice or hatred but by hope for a better world.

RICHARD RHODES is the author of 22 books, including novels and works of history, journalism, and letters. His newest, published in October 2007, is the third volume in his nuclear history, Arsenals of Folly: The Making of the Nuclear Arms Race. His The Making of the Atomic Bomb won a Pulitzer Prize, a National Book Award, and a National Book Critics Circle Award.

Section One

Explosive Discoveries and Bureaucratic Inertia

Explosive Discoveries and Bureaucratic Inertia

“Physicists had known for forty years that enormous energy was locked up in the atom. Here at last was a way to release it. [German scientist] Otto Hahn brooded on the probable military applications of the discovery and seriously considered suicide.”


Decades before the Manhattan Project, the possibility of harnessing the enormous energy inside an atom captured the imaginations of scientists and the public who foresaw a source of unlimited energy as well as enormously destructive new weapons. In 1914, novelist H. G. Wells envisioned an atomic bomb that would produce a continual radioactive explosion in The World Set Free. For Hungarian physicist Leo Szilard, the novel triggered his fascination with unleashing the energy within an atom. In 1933 while crossing the street in London, Szilard realized the possibility of a nuclear chain reaction.

Five years later, scientists still did not know which elements would create a chain reaction. Then by accident, Otto Hahn and Fritz Strassmann were able to split apart uranium atoms in Nazi Germany on December 21, 1938. Within weeks, Lise Meitner and her nephew Otto Frisch explained this physical phenomenon as “fission” of the uranium nucleus. Word spread quickly as physicists from Britain, France, Italy, Russia, and the United States rushed to duplicate the experiment by bombarding uranium with neutrons. The race to develop an atomic bomb had begun. In August 1939 Albert Einstein warned President Franklin D. Roosevelt that Germany could already have an atomic weapon underway.

Fear that Hitler would be the first to develop and use the atomic bomb galvanized the United States and Britain to invest in making an atomic bomb. More than a hundred scientists who had fled Nazi Europe joined the American and British efforts. In 1940, two such refugees in Britain, Otto Frisch and Rudolph Peierls, warned that if Germany had an atomic bomb, “No shelters are available that would be effective.… The most effective reply would be a counter-threat with a similar bomb.” In July 1941, the British MAUD report concluded that creating an atomic bomb was both feasible and urgent.

The United States was slow to embrace the undertaking. Even Vannevar Bush, President Roosevelt’s closest scientific advisor, was skeptical of the “wild notions” of atomic bombs. But by spring 1942 the compelling reports of James Chadwick and other British scientists prevailed. Bush became an ardent advocate as he told Secretary of War Henry Stimson, “Nothing should stand in the way of putting this whole affair through to conclusion, on a reasonable scale, but at the maximum speed possible.” The following selections trace the scientific discoveries on the eve of war, the compelling case for creating an atomic bomb made by British scientists, and the period of indecision that led up to the launching of the Manhattan Project.

Thinking No Pedestrian Thoughts

Eccentric Hungarian physicist Leo Szilard spent many hours thinking in the bathtub. But perhaps his most significant scientific insight occurred while he was crossing the street in London in 1933. As told here by Richard Rhodes, Szilard had just stepped off the curb when he realized the possibility of a nuclear chain reaction.

From The Making of the Atomic Bomb


In London, where Southampton Row passes Russell Square, across from the British Museum in Bloomsbury, Leo Szilard waited irritably one gray Depression morning for the stoplight to change. A trace of rain had fallen during the night; Tuesday, September 12, 1933, dawned cool, humid and dull. Drizzling rain would begin again in early afternoon. When Szilard told the story later he never mentioned his destination that morning. He may have had none; he often walked to think. In any case another destination intervened. The stoplight changed to green. Szilard stepped off the curb. As he crossed the street time cracked open before him and he saw a way to the future, death into the world and all our woe, the shape of things to come.

Szilard was not the first to realize that the neutron might slip past the positive electrical barrier of the nucleus; that realization had come to other physicists as well. But he was the first to imagine a mechanism whereby more energy might be released in the neutron’s bombardment of the nucleus than the neutron itself supplied.

There was an analogous process in chemistry. Polanyi had studied it. A comparatively small number of active particles—oxygen atoms, for example—admitted into a chemically unstable system, worked like leaven to elicit a chemical reaction at temperatures much lower than the temperature that the reaction normally required. Chain reaction, the process was called. One center of chemical reaction produces thousands of product molecules. One center occasionally has an especially favorable encounter with a reactant and instead of forming only one new center, it forms two or more, each of which is capable in turn of propagating a reaction chain.


  • "It's both a wonderful service to history and a fascinating book to read."—Walter Isaacson, author of Einstein: His Life and Universe and Leonardo Da Vinci
  • "The definitive anthology on the Manhattan Project."—Gregg Herken, author of Brotherhood of the Bomb
  • "A wonderful addition to the literature on the development of the atomic bomb. This rich anthology... enhances our knowledge of the formative years of the nuclear era and underscores the perils we still face."—Kai Bird, co-author of the Pulitzer Prize-winning American Prometheus

On Sale
Jul 7, 2020
Page Count
544 pages