I went to the most fascinating lecture about the history of the nuclear bomb last week. I’m not even going to try to shorten my notes. I want to remember it in as much detail as I possibly can. As before, my own post-lecture note interjections are [L: Highlighted like this] (I also highlighted a couple of questions I’d asked during the lecture in the same format).
Nuclear Weapons and Academic Responsibility: A Social Scientist’s Perspective on Nuclear Physics and Ethical Considerations
Peter Wallensteen, Professor Emeritus at the Department of Peace and Conflict Studies, Uppsala University. Head of department, 1972–1999.
10 Dilemmas/Universal Questions
- If Germany gets the bomb, what do we do? Do we make our own?
- Germany stopped. Should we continue?
- We have it. How do we use it? On people?
- How about a purely military target?
- Share information with Soviet Union?
- The Soviets have it. Arm more or less?
- Can you find a military use for nuclear weapons?
- Should all countries have nuclear weapons?
- Create climate for disarmament?
- Basic ethics
1. If Germany gets the bomb, what do we do? Do we make our own?
Answer: YES, make our own.
The beginning
In 1938 – 1939, it is discovered that one can control the breakup of an atom and derive significant energy from the subsequent chain reaction. This discovery was published in one of the leading physics journals in early 1939. All other physics institutions in the world read the journal. There were several leading centers for nuclear physics: Germany, Great Britain, France, and the US.
Everyone realizes we are doing something tremendously important. We can control the process of fission, which generates so much energy that weapons can be produced from it. Immediately, physicists realized this would be possible. The concern is that Germany is as advanced as any of the others in terms of nuclear physics. Why worry? Because Germany has the Nazi regime bent on controlling Europe and heavily focused on armament. What if Germany develops or obtains an atomic bomb? Should we build our own?
Physicists everywhere debated this issue. Many were Jewish refugees from Germany who knew firsthand what was happening there. They decided it was essential to make their own bomb, unwilling to allow Germany to dominate with such a weapon.
Enlisting Einstein’s reputation
They approached Einstein and said, “Albert, we think you need to write to President Roosevelt and explain the situation. You are the only scientist Roosevelt will genuinely listen to.”
Einstein was a well-known pacifist, making this request challenging for him. Eventually, others at Princeton helped him draft a letter, which he sent off. Roosevelt received it, but at that time, the US was not involved in the war. The attitude was isolationist — “We’re making America great in America, nowhere else.”
Los Alamos is born
Many deliberations occurred before the issue entered the political process. The US entered the war in 1941, deciding at that point, “Yes, we shall go for it,” launching the Manhattan Project. It was top secret — Germany must not know — but resources needed to be allocated. US Congress authorized substantial funding for this secret project. They recruited excellent scholars, young people, PhD candidates, and master’s students — anyone skilled in nuclear science. All were recruited and moved to Los Alamos. Robert Oppenheimer led the project.
The project progressed rapidly. Several involved individuals had since described the experience as fantastic. They got to live there with their families, spending their days discussing nuclear physics. Several years were dedicated to seminars aimed at solving the complex problems of building a nuclear weapon. At its peak, a few thousand people resided at Los Alamos. However, producing a nuclear weapon required even more — fission materials, uranium access, and a vast secret network. Ultimately, approximately 100,000 people were involved in various aspects, from uranium miners in the Congo to specialists in the US.
When you bring together many bright young minds, incredible things can happen. The US attempted to monitor Germany’s progress, though it was challenging to track everyone’s activities. It was evident Germany was acquiring essential materials, indicating a nuclear project. By the end of 1944, US intelligence discovered that Germany had stopped its nuclear efforts. US troops had landed in Normandy, Russian forces were advancing from the east, and it was clear Germany was in a difficult position.
2. Germany stopped. Should we continue?
Answer: YES. If not Germany, Japan.
Approx. November 1944.
The entire point is to defeat Germany. If they no longer have the nucelear weapon, then what is the purpose? People are starting to question what’s going on. Some are saying, “The idea behind this was to prevent Germany from having the weapon. If Germany doesn’t have it, we should stop the project.”
This is being debated in Los Alamos. General Groves convinces congress that the project must continue and be funded. He argues they can produce the bomb, and that was the premise under which they received the money — so they have to do it. It’s not a matter for scholars like Oppenheimer to have a guilty conscience over; it’s about the funding.
And, critically… as Germany is about to lose, they must speed up and produce it much sooner than planned. If Germany is destroyed before it’s completed, they will use it on Japan.
[L: This one got me... seemed like originally the plan was to build the bomb for deterrence purposes, but at some point in here the thinking switched to using it on _someone_, and just deciding _who_.]Decision in November 1944 was to continue the project. It proved successful, accelerated, and they kept learning. They conducted the first trial of the bomb in July 1945. By that point, Germany had already capitulated in May, leaving only Japan. Still, the US persisted in producing the weapon, even though Japan appeared likely to lose as well.
Japan was steadily losing territory. The USSR had promised that three months after Germany surrendered, it would enter the war against Japan. Since Germany capitulated on May 8–9, the Soviet Union would likely enter around August 8–9 — needing time to move troops before attacking Japan. That was the situation in July 1945.
Ultimately, the US produced the weapon and confirmed it worked. Scientists were pleased and cheered at the successful test.
Q&A in this section
Q: Germany is about to lose, but their initial objective was not to use it but just to have it… right?
That can be debated. Some thought we shouldn’t actually use it, just have it to balance Germany. That debate comes into play with the Japanese instead. They weren’t really thinking about the actual use - just that if the Germans did it, we needed to do it too. It’s an arms race you get pulled into.
Q: But if Germany were about to lose anyway, why make the bomb faster?
The information is that Germany has given up the project. So only the US is running it now, and the question becomes: should we keep going if Germany is about to lose?
Q: So why proceed, and why so fast, if US are the only ones left?
That’s the logic of the arms race — the logic of the military-industrial complex. You started it, you funded it, you finish it.
Q: Did they know what would happen to people—what it would mean?
Only vague ideas. No details. It was part of this conflict mentality: us versus them. They didn’t think too much about the human cost. You try to forget these are real people.
3. We have it. How to use it? On people?
Answer: YES. On people.
Scientists and scholars start discussing this among themselves, realizing the weapon’s extraordinary power. They saw the first explosion and felt its impact. They know that if you drop it on a city with living people, it will be extraordinarily destructive. Should it be used in some other way?
When we say “we”, we mostly mean the United States.
One opinion is that we should avoid using it on a populated or “valued” target. Perhaps we could detonate the bomb somewhere uninhabited and invite Japanese diplomats or envoys from the emperor to witness its power, thus compelling them to capitulate without actually destroying a city. In the end, however, decision-makers opt against that. Groves and other key players conclude that it must be used on a real target to demonstrate its destructive force, which means killing people.
What kind of target would that be? Maybe it can be used on some people, but… civilians?
4. How about a purely military target?
Answer: NO. We want as much impact as possible.
One idea would be to kill only military personnel — those “involved” rather than innocent civilians.
A target list existed at the time, though it was only disclosed later. Initially, Kyoto was at the top. Kyoto was highly symbolic, being an old imperial city. Destroying it would send a potent message to the Japanese that the U.S. could demolish anything — even culturally sacred sites.
Why was Kyoto removed from the list?
Henry Stimson (Secretary of War) is sometimes said to have honeymooned in Kyoto; another story is that in June he attended a dinner where his niece — who had visited Kyoto — told him how beautiful and significant it was. Supposedly, Stimson returned to his office and moved Kyoto from first place on the list to fourth. Unclear which version of events, if either, is true.
The updated list became:
- Hiroshima
- Kokura
- Nagasaki
Ultimately, the decision was to maximize impact. The White House initially claimed that the targets were purely military, but the lecturer contends Hiroshima was not a military target.
Annual ceremony in Uppsala
Every August 6 in Uppsala, there’s a ceremony where floating candles drift down the river on paper lanterns—mirroring a Japanese tradition. The lecturer helped organize one event and invited the Japanese ambassador, a Hiroshima survivor, who attended in a personal capacity. He shared his story:
His father, a high-ranking imperial official, noticed the Americans had left a few cities untouched, including Hiroshima. Believing it to be “unimportant,” he moved his family there from Tokyo. The ambassador was five years old then.
Hiroshima is mostly flat, crossed by a river. Their new home, near the river, was somewhat sheltered. When the bomb detonated overhead, it destroyed everything on the flat terrain, but their house remained. Burned survivors flocked to the river; his mother tried to help them. That was his enduring memory of Hiroshima.
Preserving cities for bombing
US had deliberately preserved several cities from conventional bombing to demonstrate the nuclear weapon — treating it as a physical experiment. While many other places were bombed with conventional weapons, these chosen cities remained intact to allow clear comparison of the bomb’s effects.
By late 1944 and into 1945, they were already deciding on the target. Hiroshima contained American prisoners of war — 27 died, and their families later sued the U.S., but without recognition.
[L: Q: How much of the decision was 'necessary to end the war' vs. 'we want to see what happens'?]
Decision-makers usually combine multiple reasons. In his memoirs, President Truman stressed that a land invasion would kill many Americans, so forcing a quicker Japanese surrender with the bomb would save U.S. lives. Plans for an autumn 1945 invasion of the Japanese main islands would have been extremely destructive. Many Americans still use the argument that the bomb saved lives.
Nagasaki
Hiroshima’s bomb was one design; a second bomb was prepared a few days later when Japan still hadn’t surrendered. The bomber crew flew to Kokura first, but it was covered by clouds, making it difficult to pinpoint the target. They faced a dilemma: land with a live nuclear bomb or pick another target? They diverted to Nagasaki, found a break in the clouds, and dropped the bomb on August 9.
Circumstances largely determined the ultimate target. Nagasaki had some industry but wasn’t a significant military base.
Afterward, the destruction was immense. A physicist was sent by the emperor to investigate Hiroshima. Japan’s nuclear program was negligible, so at first they didn’t suspect a nuclear bomb. But the investigator concluded the Americans possessed an extremely destructive device and advised the emperor to surrender. Japan had been exploring surrender via Moscow, with conditions such as preserving the emperor’s status. Yet many in the government opposed it — some samurai threatened the investigator.
Before the emperor could act, Nagasaki was bombed. On August 15, Japan surrendered, insisting the emperor remain in place.
For the U.S., the bombs achieved rapid capitulation and were deemed a success. Within weeks, American troops occupied Japan. One priority was visiting Hiroshima and Nagasaki to document the bomb’s effects.
Observations from August 6
In Hiroshima the morning of the bombing, only three planes appeared. Residents, used to huge flights heading to bomb Tokyo, weren’t overly alarmed. One plane carried the bomb, which detonated about 600 meters above ground. The other two dropped instruments by parachute to measure the explosion. These devices were retrieved later — evidence of the experiment-like nature of the attack.
A film called The Day After Trinity interviews scientists involved in the Manhattan Project. One confesses they confirmed the bomb worked exactly as planned… even though it killed about 100,000 people instantly. He struggles with the moral implications while acknowledging the technical success. Seeing it both a remarkable scientific achievement and a moral catastrophe.
By 1945, the world had entered the nuclear age. Now, more than 80 years on,the question is no longer “Should we build it?” but “How do we contain it?”
Q: Why didn’t Japan pursue nuclear weapons afterward?
It’s debated in Japan. Some push for nuclear armament, but the U.S.-imposed constitution limits it. Japanese society is split: peace advocates say, “We’re the only victims of nuclear weapons; we know their horror — why build them?”
Others argue they can’t trust the U.S. and must deter China. The Nobel Peace Prize awarded to survivors reinforced the anti-nuclear viewpoint. Japanese culture can be intricate: it’s somewhat insular and has unique attitudes about these matters.
5. Share information with Soviet Union?
Answer: NO. Do not share.
Do we share information about the nuclear weapon? Should we give it to others or keep it for ourselves? This question arose because, during the war, the U.S. collaborated heavily with the UK, French scholars, and Canada — openly sharing nuclear research. But the USSR was also an ally. Should the Soviets be informed as well? Many believed that would be wise, as it would foster better relations after the war.
Bohr’s conversation with Churchill
One leading physicist at the time, Niels Bohr from Denmark, understood the situation around 1943. Though he was in German-occupied Denmark, he developed a plan for sharing. After escaping through Sweden to London, he had the chance to speak with Winston Churchill. Bohr wanted the UK to share information on the bomb with the Soviets immediately, to build trust postwar. Churchill’s advisors warned that he only read one-page memos, and Bohr insisted on three pages. During their meeting, Churchill stood by a fireplace. After taking Bohr’s three-page memo, he tore off the last page and tossed it into the fire, did the same with the second, and signaled his refusal to share anything with the Russians. Churchill then deemed Bohr unreliable — possibly a Soviet spy — so Bohr lost his access.
Churchill decided they would not share. Whether it was wise is unknown, but by 1949 the Soviets had exploded their own nuke. Many in the U.S. assumed spies must have provided critical information. One suspect worked on the Manhattan Project, but was his intel really pivotal?
Silence spoke volumes
The lecturer described a 1980s “space bridge” teleconference (quite new at the time) linking Tufts University with a university in Moscow. Scholars in Uppsala and others were involved, and the topic was the dawn of the nuclear age. The Russians introduced an elderly scientist who had led the Soviet nuclear weapons program. He recounted approaching Stalin in 1942–43 after noticing that American, British, and Canadian physicists had abruptly stopped publishing their usual research papers. He deduced these scientists had been recruited for a secret project and reported this to Stalin, prompting the Soviet program’s start.
An acquaintance of the lecturer recalled that, at Yale, many familiar faces vanished from physics seminars without explanation. Then he received a letter from the U.S. Department of Energy, summoning him to a place called Los Alamos in New Mexico, forbidding him to say anything about it. He bought a train ticket and told the seller he was going to New Mexico. The ticket clerk said, “Oh, another one—have fun.” So, indeed, a large number of active researchers had suddenly been taken into the Manhattan Project.
During the space bridge, someone asked about Fuchs (a known spy). Did his information truly aid the Soviets? The Soviet scientist said it only confirmed they were on the right track; by that time they’d already begun and had their own program and methodology. When Bohr urged Churchill to inform the Soviets, the Russians already knew something was happening.
Withholding details only fueled suspicions, likely worsening Cold War tensions.
[L: Did not fully grasp 'space bridge' or purpose of the conference - thorough knowledge sharing or symbolic? A strict time limit on statements was mentioned.]By 1949, the Soviets tested their bomb, proving they too had the capacity. Many in the West had predicted it would take them a decade or more, yet it happened far sooner — just four years. This shifted everything: previously only the U.S. had atomic capability, and now the Soviets possessed it, too. The question then became, “What next?”
6. The Soviets Have It. Arm More or Less?
Answer: MORE
If the Soviets have the bomb, do we need more? One physicist in the Manhattan Project proposed a “double bomb” — the first bomb’s explosion igniting a second stage to create a much larger blast: the hydrogen bomb, far more destructive.
Some opposed this, questioning whether it truly helped. Wasn’t the arms race dangerous? Still, the general trend was to build more, although opponents existed.
Opponents
Initially, many opponents were nuclear physicists themselves — people linked to the Manhattan Project who became critical. Albert Einstein was strongly opposed; he had written the letter that helped start it all and now wondered if something could be done to change course. In 1955, they issued the “Russell-Einstein Manifesto”.
Bertrand Russell had won the Nobel Prize for Literature in 1950.
Q: If one bomb is so destructive, why thousands of them?
That’s their point. Isn’t one or two enough? Why 1,000, or 2,000, or 18,000? We’re now down to around 1,000 – 2,000. Opponents argued scientists have a responsibility to reverse this trend. The manifesto was published in July 1955.
Joseph Rotblat’s story during Uppsala visit
The key organizer was Joseph Rotblat, a radiologist who had been part of the Manhattan Project. In November 1944, he had voiced criticism: if the Germans no longer had the project, why continue? He had been immediately removed. He switched focus to studying nuclear weapons’ effects, particularly radiation. He also gathered prominent signatories for the manifesto and won a Nobel Prize in the mid-1990s. He had been invited to Uppsala, where he shared this story:
They had drafted the manifesto with Einstein’s full support, but needed Einstein’s signature. Rotblat sent the document to Einstein. At some point afterwards he boarded a plane in France. Partway through the flight, the pilot announced, “I regret to inform you of sad news: Professor Albert Einstein has died.”
Rotblat assumed Einstein never signed the manifesto and felt despondent. But after landing in Paris and then traveling to London, he found a letter in his mailbox bearing the heading “Institute for Advanced Study, Princeton.” Inside was the manifesto, signed by Einstein — one of his final acts.
Rotblat organized a press conference with Russell and other notables. They made a huge media impact, warning that this arms race was economically, intellectually, and morally untenable. The next step was to organize scientists.
Pugwash movement
This effort led to the Pugwash movement, launched a couple of years later in Pugwash, Nova Scotia (Canada). It provided a meeting place for scholars and scientists from the U.S. and USSR, at a time when Canada was viewed as a safer intermediary — less rigidly anti-communist than the U.S.
The Pugwash movement has been highly influential. Initially, it brought together nuclear physicists from the U.S. and USSR. Today, it has expanded to address nuclear proliferation in Iran, North Korea, and elsewhere, seeking practical ways to avert disaster. It’s an interesting disarmament movement and a direct outcome of the manifesto.
Outcomes included multiple agreements, most notably the Nuclear Non-Proliferation Treaty (NPT), in effect since 1970, preventing new states from developing nuclear weapons.
Alva Myrdal’s negotiation
One key figure in the NPT process was Alva Myrdal, a Swedish negotiator. She and her associates were impressed by the Pugwash approach. The NPT negotiations involved 18 countries — six NATO members, six Warsaw Pact, and six neutral (including Sweden and Mexico). Sweden used its neutral position to champion nuclear disarmament. Myrdal was diplomatically astute. For instance, when discussing a test-ban treaty, the West demanded verification; the Soviets resisted, calling it spying. The Americans suggested seven inspections a year, while the Soviets said they might accept three. Myrdal proposed 35 inspections over seven years (which still averages five a year) without stating it outright. Both sides found it acceptable.
Despite her skill, the major powers — Britain, the U.S., and the USSR — disliked the agreement. The British Prime Minister reportedly said, “We must stop this lady in Geneva.” Stockholm instructed her to stand down, as Sweden was a small country and the big powers opposed her proposals. Still, she was knowledgeable and managed to secure Article 6 in the NPT, requiring nuclear-armed states to work toward general and complete disarmament.
While there were significant developments through the 1970s and 1980s, in the end, the big powers largely controlled the process of nuclear negotiations.
7. Can you find a military use for nuclear weapons?
Answer: Deterrence, primarily.
Some argue that nuclear weapons serve no practical combat purpose. They primarily exist as a deterrent.
Second-strike capacity
The concept of second-strike capacity is central to deterrence. Imagine two countries each with missiles. If Country A launches a first strike and destroys Country B’s missiles on the ground, A “wins.” That’s first-strike capacity — the ability to eliminate the other side’s arsenal preemptively. To counter this, B keeps some missiles on submarines or airplanes, ensuring it can retaliate if its land-based missiles are wiped out. This is second-strike capacity: the power to respond even after a devastating attack.
Because of this, countries maintain missiles on land, in submarines, and on planes, constantly updating their systems to stay one step ahead. Each branch of the military — navy, air force, army — might want its own nuclear weapons, leading to a continued arms buildup. Talks of space-based assets arise too, though Outer Space Treaty members agreed to prohibit stationing nuclear weapons in space.
Strategic vs tactical nuclear weapons
There’s also debate over whether nuclear weapons can be used in an actual war. This leads to the distinction between strategic and tactical nuclear weapons. Tactical nukes are smaller and might be used on a battlefield. Such weapons are particularly worrisome now, given the rhetoric around wars like Ukraine, where there were concerns that Putin might consider using them. At present, he’s not emphasizing that option — he may be waiting for possible political changes elsewhere.
Scientists often argue that deterrence is somewhat more “acceptable” (relatively speaking) than actual wartime use. Tactical nukes, however, can be just as powerful as the bombs used on Hiroshima and Nagasaki.
Q: Does the NPT distinguish between tactical and strategic nuclear weapons?
No.
Q: Is there another treaty that addresses this distinction? How is it managed?
There are some specific treaties on strategic nuclear weapons, notably New START, which is the only remaining agreement limiting such arsenals. It expires in January 2026, and currently there’s no active negotiation to extend or replace it. Everything else — like tactical nukes — remains largely unregulated.
[L: If a state that already has nuclear weapons invests in more tactical nukes, are they breaking the NPT?]
No. The NPT only prohibits new countries from acquiring nuclear weapons; it doesn’t cap existing arsenals. Nations typically label new developments as “modernization,” arguing they aren’t creating new weapons but upgrading old ones. In practice, this can involve faster, stealthier missiles and other innovations.
Q: Do the U.S. and Russia have second-strike capacity in positions that allow for an assured response?
A: That’s essentially how deterrence works. Both countries maintain a “launch on warning” or “retaliation” framework, ensuring neither can be entirely disarmed by a first strike. China, however, has no comprehensive treaty with the U.S. on nuclear arms. North Korea is developing missiles that can reach the U.S. In fact, only a small fraction of nuclear issues is regulated at all. The strongest agreement remaining is the NPT. By next year, that might be the sole major treaty we still have. Meanwhile, states are also pulling out of other arms-control agreements, such as those on landmines and tension-reduction. It’s all increasingly uncertain.
Q: How close are we to having nuclear weapons stationed in space?
A: It’s a big question. We already use satellites heavily for detection and information — vital to second-strike capacity. There’s less talk of placing nukes directly in space, but more about “killer satellites” that can destroy or disable enemy satellites, thereby eliminating vital data. Formerly, President Trump created a “Space Force”, whose exact role is still unclear, but it shows how critical satellites have become. Protecting them, and preventing anti-satellite warfare, has become a significant security concern.
8. Should all countries have nuclear weapons?
Answer: The debate is ongoing.
This issue is central to the Non-Proliferation Treaty (NPT). One reason the NPT was created stems from 1950s concerns that a rearmed Germany, whose wartime scientists were still active, might develop nuclear weapons. Preventing Germany from going nuclear became a key motivation. Germany eventually joined the NPT, which was a major step.
Yet debates continue. France and Britain already had nuclear weapons — should other European nations follow suit for “European deterrence”? Some Nordic countries have questioned whether to rely on the U.S. or to develop their own arsenals. Poland and others face similar dilemmas. The more countries that acquire nuclear weapons, however, the harder it is to maintain control and avert escalation.
[L: Answering this for myself - whether it is in a country's self-interest to _get_ a nuclear weapon, and whether that should be OK - is why I'm here.]9. Create climate for disarmament?
Answer: How?
Can we even do that? Disarmament typically involves scaling down or controlling nuclear weapons. It’s difficult to make progress on this today, yet some older ideas persist, like creating nuclear-free zones or removing especially provocative weapons. One recent attempt is the 2017 TPNW (Treaty on the Prohibition of Nuclear Weapons), signed by around 120 countries. None of the nuclear-armed states signed. Nor did Sweden.
Sweden and the TPNW
Why not? Sweden stated it would stick to the NPT, believing the TPNW somehow contradicts it. Still, the previous Swedish government promised to send observers to TPNW meetings. This was done initially, but not under the current government. The former government also planned to create a Swedish “nuclear knowledge center” for academic research on disarmament. The Swedish Research Council issued a call for proposals; Uppsala University’s proposal won. That led to the establishment of the AMC (Alva Myrdal Center for Nuclear Disarmament) within the department, and this course is part of that initiative.
10. Basic ethics
We must return to fundamental questions about the ethics of being a scientist or scholar. That’s why the reading includes the Uppsala Code of Ethics for Scientists — a concise document resulting from a major project at Uppsala University roughly 40 years ago. At that time, concerns about nuclear weapons and the environment led the rector of the university to ask all faculties to discuss their responsibilities in this nuclear era. A small group formulated an ethics guideline, and the rector requested written feedback from each faculty.
- The Medical Faculty noted that ethical considerations are already integral to their work, especially in training new doctors. Nuclear war would be so destructive as to render medicine ineffective, giving them all the more reason to support prevention.
- The Law Faculty said the code was interesting but unlikely to hold up in court.
- The Theology Faculty wrote a lengthy reply pointing out that codes of ethics had existed throughout Christian history, so this was nothing new to them.
- The Social Sciences Faculty responded with just three lines: “Such a code would be an infringement on academic freedom. We reject it.” The lecturer has debated this point with the author of the response ever since.
According to the lecturer, academic freedom should be paired with responsibility — scholars ought to consider the ethics of their research topics, funding sources, methods, and the impacts of their work. His colleague, however, believes academic freedom must be absolute.
Four decades later, the debate continues. The ethics code remains unchanged, yet the lecturer argues it’s still vital to care about how science and knowledge affect society — and to avoid feeding the same forces that provoke conflict.