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Restricted Data

The History of Nuclear Secrecy in the United States

The first full history of US nuclear secrecy, from its origins in the late 1930s to our post–Cold War present.

The American atomic bomb was born in secrecy. From the moment scientists first conceived of its possibility to the bombings of Hiroshima and Nagasaki and beyond, there were efforts to control the spread of nuclear information and the newly discovered scientific facts that made such powerful weapons possible. The totalizing scientific secrecy that the atomic bomb appeared to demand was new, unusual, and very nearly unprecedented. It was foreign to American science and American democracy—and potentially incompatible with both. From the beginning, this secrecy was controversial, and it was always contested. The atomic bomb was not merely the application of science to war, but the result of decades of investment in scientific education, infrastructure, and global collaboration. If secrecy became the norm, how would science survive? 

Drawing on troves of declassified files, including records released by the government for the first time through the author’s efforts, Restricted Data traces the complex evolution of the US nuclear secrecy regime from the first whisper of the atomic bomb through the mounting tensions of the Cold War and into the early twenty-first century. A compelling history of powerful ideas at war, it tells a story that feels distinctly American: rich, sprawling, and built on the conflict between high-minded idealism and ugly, fearful power. 

An audiobook version is available.

528 pages | 12 halftones, 7 line drawings, 3 tables | 6 x 9 | © 2021

History: American History, Military History

History of Science

Physical Sciences: History and Philosophy of Physical Sciences

Political Science: Diplomacy, Foreign Policy, and International Relations


"It's a stunning achievement: a historical exercise that documents not just all the things we cannot know but all the things we only thought we couldn't know, and which Wellerstein's dogged research has dug out."

London Review of Books

"In Restricted Data, Wellerstein has drafted one of the finest blueprints of our national security apparatus by focusing on nuclear weapons, its deepest cogs and wheels. He reveals the wiles, machinations, and ruses of physicists who first kept the secrets of the nucleus. He uncovers the prevarications, leaks, and conspiracies of the officers and bureaucrats who held those physicists to account. He has found a peephole into a stadium where the most important games are played. . . . Wellerstein asks brilliant questions that reach to the heart of what secrecy and science and security mean. . . . Wellerstein takes the reader down the long path to understand what nuclear secrecy meant, guiding the reader through the subject's many tangles."

Los Angeles Review of Books

"Groundbreaking. . . . The best writers make the familiar seem foreign, challenging assumptions about a state of affairs we take for granted. It might seem obvious that building the most powerful weapon in the world, a device that could end human civilization, requires extreme secrecy. Yet Wellerstein peels back the layers of the nuclear onion to reveal a rich debate about what should be kept secret and why. . . . Wellerstein's book is compelling and frightening as it confronts the reader with the confounding questions that scientists and government officials faced when trying to decide what information should be withheld." 


"Secrecy was a defining aspect of the creation of the atomic bomb and, 75 years later, nuclear secrecy remains a feature of American democracy. In Restricted Data, Alex Wellerstein examines the health of democracy in the face of big science, big government, and big weapons."


"Wellerstein draws on a voluminous body of documentary research. . . . One of the great ironies of Restricted Data is that none of this research involved information that is currently secret. Though Wellerstein is clearly well versed in the art of filing Freedom of Information Act requests, he has no security clearance and professes not to want one. That a book of such calibre and depth can nevertheless be written is a testament both to Wellerstein's scholarship and to one of the book's central contentions: knowledge, once created, is very hard to keep secret."

Physics World

"Based on interviews and years of tireless spadework in government archives, the present book showcases [Wellerstein's] talents as a researcher and a skillful writer of narrative and analysis. One of Restricted Data's many strengths is its reconstruction of the work of those inside the state who debated, designed, and performed the day-to-day bureaucratic practices of secrecy. The effect is one of demystification."

Physics Today

"Restricted Data informs the present as much as the past. . . . The history of US nuclear secrecy is messy and fraught—all of which makes for delicious, if at times disturbing, reading."

Bulletin of the Atomic Scientists

“Fascinating, truly fascinating, and readable, and I do mean readable.”

Ploughshares Fund, Press the Button podcast

"One might suppose that nuclear secrecy is merely incidental to the larger history of nuclear weapons, but Wellerstein demonstrates that the subject is rich and dynamic and consequential enough to merit a history of its own. . . . Wellerstein is not just an accomplished historian who has done his archival homework, he is also a lively storyteller. And he leavens his narrative with surprising observations and insights. . . . [He] does an outstanding job of explaining how we got where we are today, and his analysis will help inform where we might realistically hope to go in the future. Restricted Data is bound to be the definitive work on the history of nuclear secrecy."

Federation of American Scientists

"The scope of Wellerstein's thought-provoking book spans the scientific origins of the atomic bomb in the late 1930s all the way through the early 21st century. Each chapter chronicles a key shift in how the US approach to nuclear secrecy gradually evolved over the ensuing decades—and how it still shapes our thinking about nuclear weapons and secrecy today."

Ars Technica

"An impressive and innovative monograph. . . . Restricted Data is not just a detailed chronicle of the ongoing secrecy versus anti-secrecy debate, but a profound, well researched and fluently written reflection on American social history since the Second World War, with multiple lessons to be learned."

Engineering & Technology

"An extremely detailed study."

Inference: International Review of Science

"A coherent and convincing account of the evolving ambitions and control of systems of information concerning nuclear knowledge in diverse political and social arenas, based on an impressive, wide-range corpus of primary and secondary sources, as is demonstrated by the abundance and finesse of the endnotes and bibliography. . . . The book provides meaningful insights for STS scholars, especially around the questions of the relationship of science and technology with military and national defence, laws and rights, and power and governance."


“We cannot understand our present political circumstances without knowing the origins and development of the US state secrecy apparatus. It has—for the most part—been a redacted chapter in American history books, a deficiency that historian Alex Wellerstein has boldly and capably set out to remedy in Restricted Data: The History of Nuclear Secrecy in the United States.”

Science for the People

"I’ve long believed that wrongful secrecy about our nuclear policies has endangered the survival of civilization. In Restricted Data, Wellerstein shows us how the dawn of the American atomic age ushered in a new era of state secrecy that became permanently embedded in US governance and culture. It’s a haunting look at the hidden mechanics of America’s top-secret nuclear program, and it asks vital questions about what happens when government secrecy becomes routine—and what it means for a global public left in the dark. My answer: catastrophic risk. It’s a monumental work."

Daniel Ellsberg, author of The Doomsday Machine: Confessions of a Nuclear War Planner

"How much do you know about nuclear weapons? How much don't you know? In this sweeping, insightful, and utterly original history, Wellerstein recasts the nuclear age as a fundamental struggle about controlling knowledge. He convincingly shows how everything about these weapons was, from even before their existence, tied up with a system of secrecy that has since expanded far beyond the atomic domain. Essential reading."

Michael D. Gordin, author of Red Cloud at Dawn: Truman, Stalin, and the Birth of the Atomic Monopoly

"Official secrecy is the ultimate form of government regulation, and Restricted Data explores the management of secrets about weapons that can literally destroy the world. As Wellerstein demonstrates, for the past eighty years the demands of the military have often conflicted with the needs of a democratic society. Wellerstein is one of the great nuclear historians of our time. This book is fascinating, essential reading not only for what it tells us about the origins and workings of America’s national security state but also for what it reveals about the nuclear dilemma we still face today: freedom or the illusion of safety."

Eric Schlosser, author of Fast Food Nation and Command and Control

"Wellerstein's imaginative and perceptive retelling of the history of America’s nuclear weapons will revolutionize conventional thinking and scholarship. Understanding how nuclear secrecy was often used to keep the American public ignorant—rather than America’s adversaries—goes a long way toward explaining a Cold War arsenal of thirty-one thousand nuclear weapons that made no strategic sense. Restricted Data should be read by every concerned citizen, and President Biden should make it required reading for his national security team."

Martin J. Sherwin, author of Gambling with Armageddon: Nuclear Roulette from Hiroshima to the Cuban Missile Crisis

"This book tackles a big and important subject—nuclear secrecy—and illuminates its history with a wealth of new detail. Wellerstein provides a long, sweeping overview of secrecy in the nuclear age, tracking its evolution from the pre-World War II discovery of fission to the present. He surveys a vital topic through the mastery of difficult archival sources and assembles a coherent, compelling narrative."

Peter Westwick, author of Stealth: The Secret Contest to Invent Invisible Aircraft

"It is difficult to do justice to the richness, capaciousness, and elegance of Wellerstein’s analysis in a short review... But by the tale’s end, in an exceptionally thoughtful and enlightening conclusion, not only does the reader fully understand how nuclear secrecy can be historicized and periodized—one also grasps that 'there has never been a simple, singular thing called nuclear secrecy.' And this is the best possible book you could read about it."


Table of Contents

Introduction: The terrible inhibition of the atom

Part I. The Birth of Nuclear Secrecy
1—The road to secrecy: Chain reactions, 1939–1942
2—The “best-kept secret of the war”: The Manhattan Project, 1942–1945
3—Preparing for “Publicity Day”: A wartime secret revealed, 1944–1945

Part II. The Cold War Nuclear Secrecy Regime
4—The struggle for postwar control, 1944–1947
5—“Information control” and the Atomic Energy Commission, 1947–1950
6—Peaceful atoms, dangerous scientists: The paradoxes of Cold War secrecy, 1950–1969

Part III. Challenges to Nuclear Secrecy
7—Unrestricted data: New challenges to the Cold War secrecy regime, 1964–1978
8—Secret seeking: Anti-secrecy at the end of the Cold War, 1978–1991
9—Nuclear secrecy and openness after the Cold War

Conclusion: The past and future of nuclear secrecy

Archival sources and abbreviations
Books and monographs


On the morning of August 6, 1945, the White House issued a press release that would change the world. In an instant, the existence of a vast scientific project was revealed, as well as the fruits of its labor: a “new and revolutionary” weapon, which had destroyed Hiroshima, Japan. “It is an atomic bomb,” the statement explained. “It is a harnessing of the basic power of the universe.” And prior to that moment of revelation, even the fact that the United States was interested in creating such a weapon, much less had actually created, tested, and now deployed it, had been “Top Secret,” the improper release of which could be, in principle, punished by death.
Nuclear weapons have always been surrounded by secrecy, and the American atomic bomb was born secret. From the moment that scientists first conceived of its possibility, through the massive undertaking that was its actual creation, there were efforts to control the spread of nuclear information, including the newly discovered scientific facts that made them possible. This desire for control was born out of fear. For the first scientists working on the American atomic bomb, it was a fear of a dread enemy—Nazi Germany—using said information to build their own weapons. Later, the fears shifted, as officials worried that a premature announcement of the new weapon would lessen its psychological value against the Japanese, and potentially threaten the success of the project itself. Though this secrecy emerged from fears that were originally very specific to the context of World War II, it was easily adapted to the new fears that followed, as new enemies emerged: the Soviet Union, the People’s Republic of China, North Korea, even non-state nuclear terrorists. And far more diffuse and varied fears would also promote this desire for control, with consequences ranging from the mundane (diplomatic difficulties) to the apocalyptic (global thermonuclear war).
But from the beginning, the desire for nuclear secrecy contained contradictions and complications. The scientists who had made the bomb, and had become enmeshed in its secrecy, were frequently wary. Some had supported the secrecy entirely, because they too shared the fears that motivated it. But many felt the secrecy, even if it had been necessary, was stifling. And as the war’s end grew close, new questions, and new worries, entered into their minds.
The atomic bomb was a product of science and industry, yet the fundamental principles it was based on were well known to scientists prior to the outbreak of war. How could a fact of nature be rendered effectively into a state secret, if any scientist, in any laboratory, in any country, could replicate and rediscover it? Military plans, conceived in the mind of a soldier, can be kept secret indefinitely, but can facts of physics and chemistry?
Many scientists and policymakers further asked whether science should be kept secret at all, and whether attempting to do so could be counterproductive for security. The atomic bomb was not merely the application of science to war, but the result of decades of investment in scientific education, infrastructure, and global collaboration. Secrecy, according to many of the scientists who worked under it, stifled scientific advance. If secrecy were made the norm, would science thrive, or even survive? Which would serve the nation’s security more, keeping things secret, or racing forward as fast and as openly as possible?
And the same science that allowed for the creation of nuclear weapons also appeared to offer up the possibility of cheap, abundant, and clean energy generation, among other civilian benefits. Would the fears of military uses of the atom override the hopes of its peaceful applications?
Secrecy had been a defining aspect of the work to create the atomic bomb, but would it be its future? The aforementioned White House press release about the Hiroshima attack, toward the end, addressed these questions, but left them deliberately unanswered. “It has never been the habit of the scientists of this country or the policy of this Government to withhold from the world scientific knowledge,” it explained, and noted that under normal circumstances, everything about the work would be released. But the “present circumstances” of the world—one war ending, an uneasy international situation unfolding—meant that the means of producing the atomic bomb had to be kept secret, at least for now. There would be, the statement explained, “further examination” of the question, in order to protect the nation, and indeed the rest of the world, from “the danger of sudden destruction.”
The totalizing, scientific secrecy that the atomic bomb appeared to demand was new, unusual, and very nearly unprecedented. It was foreign to both American science and American democracy, and its compatibility with either has always been an area of dispute. But the circumstances of the bomb’s creation, and the bomb itself, seemed to mandate the period of secrecy be extended, to avoid an existential risk. And that nuclear secrecy has continued, in evolving but ever-present forms, to our present day. We now find ourselves over seven decades after the end of World War II, and some three decades since the collapse of the Soviet Union, and nuclear weapons, nuclear secrecy, and nuclear fears show every appearance of being a permanent part of our present world, to the degree that for most it is nearly impossible to imagine it otherwise.
This book is a history of nuclear secrecy in the United States, from the first moments that the atomic bomb was seen as a realistic possibility in the late 1930s, through our present moment in the early twenty-first century. It is the story of how a large and varied group of people— scientists, administrators, military officers, politicians, lawyers, judges, journalists, activists, and the broader public—grappled with the question of whether nuclear knowledge should be regarded as something that needed to be controlled, and how many of the fruits of their discussions, policies, and interventions shaped the American national security state that endures to this day. The singular motif that reappears throughout this work is that of tension. The bomb may have been born in secrecy, but that secrecy was always controversial and always contested.
The concerns about the compatibility of science and secrecy were always joined by concerns about the compatibility of secrecy and democracy. The United States has, since its eighteenth-century origins, enshrined Enlightenment ideals of openness and freedom of speech in its core institutions. These ideals have never been treated as absolutes, but they have come with real legal, political, and rhetorical power. In practice, this has meant that while secrecy has flourished in the post–World War II American context, it has never been unlimited in its scope, even with a threat as seemingly expansive and existential as the global development of nuclear weapons.
It has also meant that secrecy reform and nuclear policy have always been in tension with democratic desires. The physicist J. Robert Oppenheimer, who had done much to create both the weapons and their secrecy, referred to the difficulty of public deliberation as the “terrible inhibition of the atom,” and it was both a badge and burden to be borne by those with access to the secrets. The secrecy, many like Oppenheimer believed, ultimately contorted American policymaking, and left the American public dangerously ignorant of the evolving national and world situation
These tensions, between the ideals of science and secrecy on the one hand, and of desires for openness and security on the other, are what make the history of nuclear secrecy in the United States unpredictable, surprising, and, at times, bizarre. In one telling example (discussed at length in chapter 3): while the United States may have been the first country to make an atomic bomb, it was also the first country to release a technical history of the atomic bomb, only days after its first use, and it did so in the interest of both improving democratic discourse and preserving further secrecy. That such a document could be created at all, rendering into plain and unified discussion the work of the Manhattan Project that had been previously enshrouded with code words and a “need to know” compartmentalization, is strange enough by itself, and no other country has done anything similar since. But that the top scientific, military, and political representatives on the project would all agree to its utility, and lobby to the President personally for its release only days after the Nagasaki attack, is a remarkable example of the ways in which secrecy and revelation are not only paired, but can serve many different ideologies and institutional goals.

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