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Restricted Data: The History of Nuclear Secrecy in the United States

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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 rich, sprawling, and built on the conflict between high-minded idealism and ugly, fearful power. 

528 pages, Hardcover

First published January 1, 2021

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About the author

Alex Wellerstein

3 books18 followers
Alex Wellerstein is a historian of science at the Stevens Institute of Technology who studies the history of nuclear weapons. He is the creator of NUKEMAP.

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Displaying 1 - 30 of 34 reviews
Profile Image for Mark.
1,239 reviews145 followers
September 19, 2022
The announcement on August 6, 1945 that an atomic bomb had been dropped on Hiroshima was not just a statement of the success of the Manhattan Project, but of the efforts to keep their development of it secret from the rest of the world. The scope of this success was all the more remarkable given the tens of thousands of people involved with it and the enormous amount of money and materiel required to turn the bomb from theory into reality. Not only did this deter an arms race, it magnified the shock effect of such a weapon and may have helped to end the war sooner as a result.

In the decades that followed, the secrecy associated with atomic weapons became accepted by most people as both necessary and wise. This has the effect, though, of obscuring the novelty of such secrecy at that time. As Alex Wellerstein makes clear, government secrecy was far from the norm in the United States prior to the 1940s, and the Manhattan Project did much to change this. Wellerstein’s book provides a detailed account of the emergence of this regime of secrecy and how it became an embedded part of American nuclear culture.

As Wellerstein explains, nuclear secrecy was a product of fear. This fear predated even the effort to build the bomb, as scientists such as Leo Szilard debated during the 1930s whether to censor themselves rather than to promote the development of such a destructive technology. While this broke down in the absence of any effective enforcement mechanism, it probably aided their willingness to accept a government-imposed secrecy regime, especially given that the goal of such an effort was to keep the secrets of the atom bomb out of the reach of a Nazi regime that many of them had fled.

This acceptance was tested sorely by the procedures that developed around the Manhattan Project. Under the direction of Leslie Groves, secrecy was maintained through a combination of isolation and compartmentalization. By locating the massive engineering works and design efforts in remote locations and restricting knowledge solely to what people needed to know in order to do their jobs, Groves hoped to limit the possibility of leaks that would alert the Germans and Japanese to their efforts. While Wellerstein considers the boast that the Manhattan Project was “the best kept secret of the war” to be more hyperbole than reality, he does regard it as successful in its primary goal of keeping the development of atomic weapons a secret from the Axis powers.

The onset of the Cold War served to justify the continuation of this secrecy regime. Though Wellerstein acknowledges that some degree of nuclear secrecy during the postwar was inevitable, he notes that there were alternatives to what developed. The focus throughout was on the control of knowledge: specifically, the details of the bombs’ designs and the techniques for processing the enriched uranium and plutonium needed to construct them. Revelations about Soviet espionage erased any lingering doubts about the need for such secrecy, and they also had the effect of making knowledge about the bomb seem as much of a threat to national security as the bomb itself.

While this regime was strained by peaceful nuclear initiatives (such as President Dwight Eisenhower’s “Atoms for Peace” program) and hostility towards the limitations it imposed on research into nuclear fusion, it largely remained in place until the 1970s, when it came under assault from the post-Watergate hostility towards government secrecy. As part of the new wave of anti-secrecy efforts, a small but determined number of students and peace activists sought to expose the major secrets of nuclear weaponry, most notably the design of the hydrogen bomb. In this they faced a government unprepared for the oblique approach they adopted, which treated the censorship of a submitted article as confirmation that the details were correct. This turned the question of nuclear secrecy from one of freedom of research into one of freedom of speech, which the government found much more difficult to restrict. Though the constrained efforts to maintain nuclear secrets, it did not completely defeat them as the persistence of such efforts down to the present-day attests.

Wellerstein’s book is a superb study of an important dynamic in American public life that is too often taken for granted. In it he manages the difficult task of finding a new angle on a familiar subject and using it as stepping stone to a much wider examination than seems possible. This allows him to shed light on how something that was seen as truly unusual became the norm, not just in the realm of nuclear weapons development but across a wide range of American public life. It is for this reason why this is a book that should be read not just by those interested in the history of the atomic bomb or of the development of nuclear technology, but anyone who is fascinated by government secrets more generally and how they came to be so closely guarded.
Profile Image for Michael Burnam-Fink.
1,674 reviews290 followers
September 19, 2022
A longer review will follow, but Restricted Data is a close look at the practice of American nuclear secrecy. These days, we take the whole complex of classification as a fact of nature, much like the fissile possibilities of U-235. But of course, classification is whole artificial, a political system born out the Manhattan Project. And while classification may seem simple, a wall between the open ordinary world and the official secrets of the states, the reality is anything but simple.

The first regime of nuclear secrecy was purely voluntary. Leo Szilard recognized the military power of his idea of a self-sustaining nuclear reaction, and assigned the patent to the British royalty. As fascism role in Germany, he embarked on a not very successful campaign to halt publication on fission research. While pre-war activity could be tracked by who stopped publishing, the barriers to the bomb were primarily logistical. Only the United States could afford the expense of isotope separation and then bomb design. Classification in the Manhattan project was a system of compartmentalization, designed mostly to protect against leaks, and penetrated in key places by Soviet spies like Klaus Fuchs.

The category of Top Secret was actually invented for the Manhattan Project. Where the story gets weird is that immediately after the bombings of Hiroshima and Nagasaki, a concerted press effort from popular articles to the technical Smythe report discussed the bomb, create a world where some facts were public and others denied. The category of "Restricted Data" related to anything about science that could be used to make an atom bomb, basic scientific facts rather than the military secrets of defense plans and names of spies.

Since 1945, the story has been one of unwinding of secrecy, with categories of civilian nuclear science around power plants, and activist efforts to reconstruct the Teller-Ulam hydrogen bomb configuration from publicly available data in the 1970s. Modern nuclear non-proliferation is based on control of material: uranium ore and centrifuges, rather than control of knowledge. But even so, the world of nuclear secrecy is vast, a black monolith in a supposedly democratic state. Thinking about nuclear secrecy reveals many paradoxes.
Profile Image for Steve.
385 reviews1 follower
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November 28, 2021
Fear is the word. Oh, what happens when fear is allowed to permeate public policy, which causes me to think that any time we suspect government acting under the umbrella of fear we must be very, very suspicious, if not default to immediate criticism. The secret shroud around nuclear research, the subject of this work, emerged just prior to our entry to WWII at the suggestion of investigating scientists themselves. The intensity of our secret state, which then grew like a mushroom cloud, has since ebbed and flowed through the years and has naturally served to advance agendas other than those publicly promoted.
Keeping the bomb secret from people who doubted the wisdom of spending thousands of millions of dollars on physics projects may have been more important to the success of the Manhattan Project than keeping the bomb secret from the Germans. A Nazi atomic effort did not have the power to stop the American work in its tracks—only Congress could do that.
This book felt balanced, thorough, and comprehensive, allowing a solid understanding of the emergence and subsequent maintenance of our security state. Professor Wellerstein does note that while we may find our national secrecy policies objectionable, most, if not all, nuclear states provide little to no insight into their programs. There’s an awful lot of grey between the black and white of this tale.
Profile Image for Kathryn Huff.
Author 1 book17 followers
August 22, 2023
I loved this book and I recommend it to everyone in the nuclear energy field. Even quite a while after reading it, I think about it often in my work at the intersection of nuclear energy technology and policy. It's entertaining, based in solid facts, and framed in key questions regarding the foundational philosophical tension between open science and nuclear information control.
Profile Image for Nick Black.
Author 2 books879 followers
January 6, 2022
had several answers to long-wondered questions, most particularly "what are the redacted portions of i.i.rabi's response at the oppenheimer security hearings" (spoiler: "super bombs", an incredibly underwhelming reveal; i'd always hoped for something like "antimatter chunks" or "neural disruptors" or "penguins that run around with spears"). no mention of carey sublette, somewhat surprising. weird that i had to go to the bibliography to find out footnote 151 referenced Mills' the seventh power; like, why not just give me the title there, as opposed to "a widely-reviewed novel"? pretty solid.

also, the only person outside of Barroso to make explicit the link between inertial confinement fusion papers and essential verification of Sublette's ablation hypothesis.
Profile Image for Isaac Weiss.
10 reviews
May 24, 2025
I've been meaning to read this one for a long time and I'm glad that I did! As someone who did not grow up during the cold war, this book does an excellent job of looking at the world of nuclear secrecy and its effects on public (and private) policy in the United States. Highly recommend this book to anyone and everyone!

Also have to make note that it was nice to hear Arthur Compton get mentioned a lot. #GoScots!
Profile Image for Craig Werner.
Author 17 books216 followers
October 7, 2022
Densely detailed study of the complexities and contradictions of U.S. policy on keeping nuclear research secrete. There's a fundamental tension between the claims of the military and business interests that's never been anything resembling resolved.
Profile Image for Gert.
65 reviews1 follower
July 30, 2021
Wow! What a detailed and erudite piece of work. So obvious when reading that this subject is not simply Mr. Wellerstein's "field of scientific research", it is clearly his passion. A pleasure to read and I learned a lot from it.
42 reviews1 follower
May 12, 2022
It's hard to imagine any discussion of nuclear weapons without the word "secret" coming up at some point. Indeed, the advent of nuclear weapons created the security regime that, in the United States at least, remains with us today. This book chronicles how it all came about. It's a history of the atomic age, but with a difference. It is often said that secrecy is incompatible with a free society, and with science. Neither is actually true. For all their talk about sharing information, scientists also partake in secrecy to protect the primacy of their work, because there is neither fame nor fortune in being the second to discover something.

Alex Wellerstein is a professor of Science and Technology Studies at the Stevens Institute of Technology. His passion is nuclear secrecy - the cloak of secrecy that surrounds the design, development and history of nuclear weapons. This was the subject of his doctoral. That it took ten years to appear in book form makes me feel a little better about mine. Like many before and since, he has been intrigued and captivated by the mysterious world of the nuclear arsenal. This passion comes across in his engaging prose, familiar to readers of his blog, which is a good port of call for all the latest information on nuclear technology. One can obtain a security clearance and enter the mysterious world, but once you do that the mystery becomes a secret, and you can't tell anyone.

This book explains why the secrecy is fundamentally flawed, but also how and why it still carries on regardless, cognisant of its own contradictions. Wellerstein examines the impact of security, but it remains elusive and hard to pin down. Did espionage and security breaches help the Soviet Union and other nations like India and Israel develop their own nuclear weapons? Certainly; but the extent of the impact is hard to measure. This book provides a roller coaster ride through three quarters of a century of security that many will find interesting, engaging and entertaining.
649 reviews7 followers
July 24, 2021
This history of nuclear secrecy in the United States highlights the clear competing goals: liberty and security. Wellerstein questions how useful the secrecy is (e.g. even if the Soviets hadn't had spies, secrecy probably wouldn't have slowed down their nuclear program much), and points out the cost to liberty is real (e.g. it pretty much aborted industrial laser fusion). That's where he spends most of the book. But at the same time, he does acknowledge the competing good - we really don't want other powers using nuclear weapons. In the end, he doesn't attempt any recommendations.

Perhaps this imbalance is a flaw in his book, but perhaps it's inherent in the story he's trying to tell. The characters in the story of American nuclear secrecy are the American government and American citizens who interact with it in some way - which usually means opposing it. Maybe there's enough information to tell the story of foreign nuclear programs, but that's a different story barely interacting. And, terrorists' nuclear efforts are clearly unknown. At least with the story of computer security, you can talk about successful hacks. But thankfully, there've been no nuclear wars to talk about.

All in all, I'm not sure I got much from this book. I'm glad the story is told, but the only conclusion I drew is that the whole national security establishment really is a new post-WWII creation - apparently, the whole concept of classified information originated in the war. That might be a regrettable thing, but is the alternative any better? I'm reminded of Heinlein's chilling 1941 short story "Solution Unsatisfactory," where it turns out a worldwide dictatorship is the only way to stop nuclear proliferation... and our narrator can't think of any better ideas. Wellerstein - though, thankfully, we're in a world where nuclear weapons are harder to make than in that story - doesn't even attempt to think of alternatives.
Profile Image for Ash Jogalekar.
26 reviews80 followers
August 7, 2023
With its culture of open debate and dissemination, science would seem intrinsically opposed to secrecy. So it was unsurprising that a severe conflict would arise with the discovery of nuclear energy and the building of nuclear weapons in which ivory tower scientists would be forced to contend with making the results of their work secret. The resulting dilemmas, political debates, issues of personal loyalty and disloyalty and in fact the very nature of scientific discovery are the subject of Alex Wellerstein's deeply researched and scholarly book, "Restricted Data".

Using a handful of examples drawn from World War II and the Cold War including Robert Oppenheimer's infamous security clearance hearing, John Aristotle Philips's theoretical design of a nuclear bomb using publicly available sources and Howard Morland's celebrated court case dwelling on his controversial article on the details of the hydrogen bomb in Progressive magazine, Wellerstein deftly unpacks the regime of nuclear secrecy and challenges to it that have enveloped the development of nuclear weapons since their very beginnings and the constant tussle between government officials and common citizens to uncover nuclear secrets.

The book is also a meditation on the very nature of secrecy, and Wellerstein applies lessons drawn from nuclear weapons to biological and medical research, lessons that are all too relevant in our age of engineered viruses and pandemics. Neither dismissing the need for secrecy nor celebrating its blanket uses, Wellerstein makes it clear that there are good questions here and no easy answers. A revealing read.
576 reviews10 followers
February 8, 2022
"Along with the presidential statement to be released after the use of the bomb, a separate, longer statement was prepared by the office of the Secretary of War. It was to be released some time later to fill in the gaps that would inevitably be left by the pithy presidential release. Drafted by Arthur Page in late June, it covered detailed policy decisions that led to the building of the bomb, including the names of people involved, filling out ten pages of text. This statement was also reviewed by a battery of readers, including members of the British delegation, in order to satisfy the requirements of the Quebec Agreement of 1943, in which the United States and Britain agreed not to disclose information on the project to third parties without mutual consent. A final version of the presidential statement was sent by Stimson to Truman by a cable on July 31, 1945, noting that the use of the weapon was imminent. Truman immediately cabled back his assent: 'Release when ready but not sooner than 2 August.' This approval of the press release is the closest thing we have to a positive written order by Truman to use the bomb. It highlights the importance that 'Publicity' had within the project that his positive assent was never requested for the use of the bomb, only the press release about it."
21 reviews
January 20, 2025
A very good insight into the secrecy question around nuclear technology. Nuclear secrecy is a strange subplot to the scientific study itself, and the book does a very good job of explaining how the existing regime began and developed over time. My qualm is particularly with the way the book traverses time; it spends extensive time on the early days of nuclear development, but then becomes repetitive and a bit more sparse as it reaches more recent decades. Some of that is undoubtedly down to the relative lack of availability of source information given the secrecy regime itself.

But some of it is, I think, missed opportunity; the book doesn’t spend nearly as much time as I think it could have going into the way the secrecy system developed in other areas and comparing it to nuclear secrecy, and discussed how U.S. secrecy developed while other states developed their own weapons, programs, and secrecy systems. This subject is touched on, but only hardly, and I think that changes how effective the book is in discussing the overarching nuclear secrecy regime itself, making the first half invaluable but the second half seem less complete and detailed. Still, a great read for anyone curious about this system and the stories related to early development of the nuclear bomb itself.
2,112 reviews18 followers
February 7, 2022
(Audiobook) (2.5 stars) This book is about the US nuclear program in the US. Or, more directly, the struggle to balance secrecy and scientific advancement in the history of the program. It goes back to the start of the Manhattan Project, and the challenge the scientists faced in following government guidelines, but also scientific principles. It was not an easy balance, and there were plenty of errors/pratfalls and massive leaks. It did not get any easier as the Cold War evolved. Between foreign actors and government infighting, it was a wonder that anything remained classified and that anything ever got done. We are still trying to determine if such classifications are effective, or how it could be made more effective.

Overall, there is good history there, but the subject matter delves quickly into legalize and government bureaucratic infighting, which is not always the greatest in story-telling. If you work in that field or are studying the history of the Cold War, perhaps it is worth the time, but otherwise, I might not spend a lot of time with this one.
Profile Image for Lojicholia .
173 reviews1 follower
July 22, 2024
This is a dense book on the history of two things: the design of nuclear weapons and the classification of their associated data. I personally took away a fair amount of learning from the cases and reasoning as to how we got here, and it was fascinating to see how we ended up with the secrecy regimes we did. It also was interesting to see the personalities involved: Oppenheimer, of course, but also Teller, Lawrence, Brueckner, all having various impacts at various times (and also interesting to hear that Teller was still having impacts into Clinton’s DOE).

I would say, nuclear weapons aside, this is an incredibly interesting study of the history of control schemes and classification systems for anyone interested in those topics, even if it’s focused mainly on TS-RD and RD more broadly. I don’t often think in terms of “must read,” but certainly think it likely applies here if you’re interested in control schemes, data classification, and the like.
Profile Image for Nick.
572 reviews28 followers
June 23, 2021
As a fan of Alex Wellerstein's Restricted Data blog I picked up his first published book on the topic as soon as it came out. It's a dense read and provides an interesting overview of a topic that's often glossed over in earlier discussions of the bomb: how did the policymakers deal with the revelation of the atomic bomb, and how did they decide what to reveal and what to keep secret? Answering that question, and tracking the evolution of the nuclear secrecy system from Word War II to the War on Terror is the book's objective and I'd say it does a good job of examining how the balance of secrecy and openness have changed with time.

Probably not for a general audience, but people interested in nuclear weapons history or how government operates will find a well-sourced, in-depth discussion.
Profile Image for Eric Johnson.
Author 22 books142 followers
June 10, 2024
What started from the first atomic bomb to the nukes of today, this book covers the complex of security of. While not exhaustive, it does go over most of the secrecy around nuclear weapons in general, regardless of tonnage and the like. What this isn't about is nuclear weapons, effects, and the like. It's merely about the secrecy around such weapons and how it evolved from the first bombs dropped on Hiroshima and Nagasaki. It mainly centers on WWII to the end of the Cold War and that's about it. It's a good book and informative, though it did seem to be nearly exhaustive, making it a well-researched book about the subject. It doesn't go over actual procedures, such as what is classified as "classified" and so on, but gives a good overview of the subject I think.
Profile Image for Jeff Greason.
290 reviews12 followers
June 30, 2023
Interesting history of the origin of nuclear secrecy in the United States and its evolution through to the immediate post-Cold-War era. Sadly it breaks off before the Patriot Act era and I would have been interested to see a similar treatment carrying forward. The author makes an attempt to be reasonably even-handed in the arguments made and how past issues were cast -- not a story of heroes and villians, but a story of how people at the time grappling with the issues cobbled together a patchwork of not-very-successful attempts to deal with knowledge deemed 'dangerous'
Profile Image for Sarah.
892 reviews
May 25, 2024
A great, in-depth examination of nuclear secrecy from before the Second World War and the Manhattan Project all the way up to our current post-9/11 geopolitical world. I wish it had gone further into the current state of secrecy but I can see why the author didn't spend so much time on that. It's fascinating to learn about how the pre-DOE agencies dealt with matters of secrecy, security, and classification. Would recommend to anyone who is keenly interested in the behind the scenes policy work touched on in the Chris Nolan film Oppenheimer.
Profile Image for Trevor Owens.
Author 7 books56 followers
July 7, 2024
I highly recommend this book to anyone interested in the history of the physical sciences or the history of the U.S. federal government. It offers a rich nuanced tour of eighty years of efforts to establish and maintain nuclear secrecy. The story is at points funny and absurd but throughout all of that absurdity, we gain insight into the major challenges that emerge from competing values around freedom of expression, openness in science, and the need to mitigate the massive potential harms that can come from nuclear proliferation.
153 reviews1 follower
November 30, 2021
The early chapters covering the debates on scientific openness and ownership of intellectual property were a slog but the the meticulous research on the history nuclear security state is deeply rewarding.

Profile Image for David.
26 reviews
January 4, 2022
Surprisingly interesting. It may start a little slow, but the story rolls along at a steady in a very logical manner. I found the subject presented well, and I appreciate the effort the author took to research his facts.
This entire review has been hidden because of spoilers.
Profile Image for Justin.
54 reviews
October 31, 2022
Phenomenal book - well researched and even better written. Read for a law review article in writing, but enjoyed it in my free time. Hard to beat Wellerstein’s combo of academic rigor and compelling prose to tell the interesting and complex story of nuclear secrecy.
Profile Image for John.
105 reviews2 followers
February 4, 2023
Nuclear weapons, Cold War, espionage are some of my non-fiction reading interests and Restricted Data scratched that itch quite well. Very interesting history and perspective on secrecy and classification that made me think.
Profile Image for Jeremy Kamp.
9 reviews
February 22, 2022
Very well written and researched book, doesn't get into the technical weeds so most everybody can understand everything in this book.
Profile Image for David Nguyen.
42 reviews1 follower
January 8, 2023
Paired well with the movie Oppenheimer. I always prefer the nonfiction version of history.
Profile Image for Richard Maguire.
14 reviews
February 4, 2023
Not what I thought it was when I set out to read it. I thought this was going to be a discussion of the technologies - instead, it was an interesting history of the secrecy regime itself. Very engaging, very approachable, very interesting.
Profile Image for Sandy.
58 reviews
February 25, 2025
I listened to the audiobook version of this. It was an excellent listen. A bunch of good information that I didn't previously know. If you're interested in the Cold war, this is well worth your time.
Profile Image for S M.
1 review
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May 29, 2025
Presented good information on an interesting topic.

Would have been better with fewer typos, (fewer parentheses), and more in-depth explanations and fleshed-out analyses.
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