Nuclear Museum Logo
Nuclear Museum Logo

National Museum of Nuclear Science & History

Joseph Rotblat’s Interview

Manhattan Project Locations:

Joseph Rotblat was a British-naturalized Polish physicist, 1995 Nobel Peace Prize winner, and founder of the Pugwash Conferences. Rotblat and his friend James Chadwick, discoverer of the neutron, conducted early research on the atomic bomb in England, and both joined the British Mission at Los Alamos working on the Manhattan Project. Rotblat left the Manhattan Project on grounds of conscience in late 1944 when it became clear Germany was not close to developing an atomic bomb—the only scientist to leave the project for moral reasons. In this interview, he discusses his personal and professional relationships with J. Robert Oppenheimer, Niels Bohr, and the Chadwick family. He also provides insight into the intense security measures in place at Los Alamos, as well as the nature of British involvement at the site. Perhaps most intriguing is Roblat’s discussion of his decision to leave Los Alamos, spurred on by his growing concern that the nuclear weapons being created were also meant for the Soviet Union, and his anxiety over a postwar arms race. In a lighter vein, Rotblat also recalls his work as a technical advisor on the 1980 miniseries “Oppenheimer.”

Date of Interview:
October 16, 1989
Location of the Interview:


Martin Sherwin: This is an interview with Professor Joseph Rotblat, R-O-T-B-L-A-T, at his office in London. Well it really was quite a production. Seven hours!

Joseph Rotblat: Yes, oh yes, quite a production.

Sherwin: I thought Sam Waterston played a marvelous part.

Rotblat: Who?

Sherwin: The person who played [J. Robert] Oppenheimer.

Rotblat: Oh, yes, definitely. He played Oppenheimer very well, and I think that the person who played General Groves was really marvelous. At one stage, I came down to the rehearsals and I went into the studio. For a moment, I am back and there, and that he was sitting in his uniform. I could tell there he goes again. Really!

Sherwin: “I have died and instead of going to heaven, I have gone back to Los Alamos.” [Laughter]

Rotblat: Some of these difficulties with what I had with this writer, [inaudible], he is an obstinate man. He had to defer to me on scientific matters. But when it came to the other aspects of Oppenheimer’s life, of course he sent this mass script. 

Sherwin: In print?

Rotblat: Yes. As he wanted to. One interesting thing was, he put in [James] Chadwick, who was a very close friend of mine. You know about Chadwick?

Sherwin: Yes.

Rotblat: He described him as a little man with a tiny moustache and a shabby overcoat. A bit like Columbo, you know, Lieutenant Columbo. Exactly opposite to Chadwick. He was entirely the other way—clean shaven, always immaculately dressed and clothed. So I told him, “Look, this is not Chadwick at all.” We argued and argued about this, because I was concerned about the [inaudible] of my friend.

Sherwin: Of course.

Rotblat: The end result was, he wrote him out completely. That was a [inaudible] to me. So Chadwick does not appear at all.

Sherwin: I did not think that the script was as good as it should have been. I thought that he made the characters very one-dimensional. Kitty was kind of nasty and a drunk when he first came here in the ’30s. Everybody sort of had a label rather than a personality. But nevertheless, it was quite a special kind of production.

Rotblat: I doubt that I have anything that I can add to what you have already researched on Oppenheimer. I knew him not so very well. I only met him for the first time in Los Alamos.

Sherwin: Right.

Rotblat: Afterwards, I saw him on maybe one or two occasions only.

Sherwin: But what I would like to do is to try to recollect as much as we can this morning about your experiences at Los Alamos with respect to Oppenheimer. When did you arrive there?

Rotblat: In January 1944.

Sherwin: Okay.

Rotblat: Yes.

Sherwin: Do you remember the first time you met him?

Rotblat: Yes, it was the day after my arrival. I was coming down from Santa Fe. I was asked to come in and talk to him. He usually liked receiving newcomers who came there. I had sort of a preliminary chat with him at the time, about the usual things, civilities, and then what I planned to do, roughly.

But immediately he struck me as a person, very quick, highly intelligent. I think he had good information. I noticed straightaway that he can take things in almost instantaneously, and he gets the grasp.  If you come to him with an idea, he would immediately see it as a major part of this important thing.

Sherwin: More clearly than the rest of them.

Rotblat: Exactly! You could then present it in a way which is much better than the original was. From this point, he is a genius. I am not surprised that he managed to be such a good director for the laboratory. This is one quality which is most important in a place like Los Alamos, where you had so many people with original ideas, but not always capable to present them in a coherent form. He really could master this. Then of course, I was invited to his house.

Sherwin: Before we talk about that, what was it that you were going to work on at Los Alamos?

Rotblat: At the beginning, it wasn’t quite clear what we should do. The British team arrived, and it was not quite clear how they were going to fit in with the other work going on. Different members of the British team were allocated to different divisions in Los Alamos. I was allocated to the L Division, the cyclotron. The idea which I had was to follow to a certain extent the work which I had been doing before, namely, I had been particular interested in the inelastic scattering of neutrons [inaudible]. 

Part of inelastic scattering, of course, is the emission of gamma rays. One did not know how many gamma rays [inaudible] and how this would affect the overall performance. So it is important to find out how many gamma rays are emitted. So I had to check up on an experiment, which I had tried to make a coincidence between gamma rays and fission, just to make sure that only the gamma rays which accompanied the fission would be recorded.

This was, of course, was the main job which I did. In this division, we had to use the cyclotron for the radiation, but it took me some time to build the apparatus and then to do the experiment.

Sherwin: Did Oppenheimer have any ideas about that?

Rotblat: Well, no, he listened to me. This was not the first week, this was about a week or so afterwards. When I came, we did not go into discussions of my particular project. He let me settle down, to find what going on, to talk to people. It was only about a week or so later that I came to lead the project. I think immediately he saw what was required, what needs to be done.

He got the grasp of it. Really the contrast between him and Niels Bohr, who didn’t understand at all the experiments. When I talked to Niels Bohr, he could not follow at all. Afterwards, when I had [inaudible] I couldn’t understand and I came to Bohr for a possible explanation, and he put it in a very weird explanation. He can be [inaudible]. Then I went to Oppenheimer. He [inaudible] some suggestions which I had to test to know to be correct.

But I think both of these people were theoretical physicists, and yet Bohr had no idea about experiments. But Oppenheimer did have a very good approach to the experimental problem.

Sherwin: I’m actually very interested in this, because I have written some about Bohr. It is my belief—and please tell me if you agree or disagree—that Bohr was a great hero for Oppenheimer. I think that Oppenheimer got many of his ideas about social implications and nuclear weapons and what happens with international relations from Niels Bohr.  

Rotblat: I don’t know this directly, but I am sure this must be the case, because I also had these ideas from Bohr. I know that Bohr liked to talk about them very much. Of course, this is my awakening of the personal responsibility of scientists came out of this, through my conversations with Bohr.

Sherwin: At Los Alamos?

Rotblat: At Los Alamos, yeah. It was the first time that I recognized it. We’d been before in touch by correspondence, but this was the first time I met Niels Bohr. I had the chance to call up these ideas, not only on how they actually worked on the project, but also on the political aspect.

Sherwin: Did you observe any discussions between Oppenheimer and Bohr?

Rotblat: Yes, on rare occasions, we used to meet sometimes in the evenings with different people and discuss political issues—not shop, [inaudible] but mostly political issues. Sometimes Oppenheimer would be there, sometimes Bohr would be there, and occasionally the both of them would be there. But there were lots of people, usually about twenty or twenty-five people, who would come to these talks. Therefore [inaudible].

Sherwin: I am very interested in those talks, which have had a way of sort of disappearing in the interstices of historical memory, because there is no record of them and people just have very vague recollection. Can you recall any specific incidents?

Rotblat: Well, one specific thing which comes to mind is, “What is to be done with Germany after the war?” The idea of dividing Germany—I cannot remember who actually put it forward—but this was [inaudible] generally, people did not think about the division of Germany in East and West.

Yet there, you see already this was put forward and discussed as one way avoiding the menace of the future with another Hitler coming up. This was the suggestion made then. [Inaudible] specifically because I remember clearly, because at that time it looked to me, I still was one of the younger people at the time, among the group, and they turned to me. It was so drastic that it stuck in my mind.

Similar discussions also were about the Far East situation [inaudible.] This is the sort of thing which we would be discussing.

Sherwin: Was there any discussion about the bomb in the post-war period, or the use of the bomb? 

Rotblat: Not very much at these meetings, no. We tried to avoid talking about the immediate sort of things, and were much more general politics. I used to talk to individual people, but not at these discussions, because [inaudible].

The thing which I discussed about the actual site was security. There was Captain [Peer] De Silva, of the intelligence, he was there. I remember particularly one meeting Johnny von Neumann—Silva boasted about the security, and von Neumann said, “I’ll bet you $25 that I shall bring in the scientists into the site and you would not know a thing about it.”

And he took him up on it. He said, “Oh yes, it is impossible.”

Then in about a week we met again, and De Silva said to him, “I have to go throw up, because I looked into it, it is possible.” He admitted it. Of course, you know about the story of the hole in the fence?

Sherwin: Yes, for people going in and out.

Rotblat: Particular Dick Feynman. He used to drive them crazy. He would go in and sign and come around and sign in again. He would go do it a number of times, and never go out.

Sherwin: That one I had not heard about. The one I’ve heard about is that he would open up safes and leave them open.

Rotblat: Oh yes, this is the other part, because also the people used 235 or 238 as a number, because you had three numbers, you had three digits. He would open [inaudible] I do not know exactly. But this business of him—

Sherwin: He used 235, the number?

Rotblat: Our safes had been locked, the combination. It is the first time we had these, and we were asked to put in three digits. So most of the people put in either 235 or 238.

Sherwin: Why?

Rotblat: Because of the uranium.

Sherwin: Oh yes, 235 or 238, of course.

Rotblat: Exactly, yes. So we could remember this sort of thing. [Inaudible] He had to guess what these numbers could be.

I know I told you the story when I was staying with the Chadwicks, and he had twin daughters. And one Sunday, we went out with Lady Chadwick and the twins and myself for a walk. We went through the gate properly, signing out. Chadwick stayed behind to do some work. We had a very long walk and came back along the fence, but you actually could see the Chadwick house quite close.

But to get into it we had to go a longer way to the gate and then back you see there, quite a few miles. Then I noticed if this fence was lifted, if lay down you lay flat on the floor, then you could crawl through. So I suggested to Lady Chadwick, “Maybe we should take this shortcut.” I did it jokingly, because I knew she was very prim and she would never do anything improper.

But she must have been very tired, because she agreed. So each of us in turn, we laid out flat and went through. No sooner were we through, then the jeep came along, the patrol. They were itching, you see, for some action. I could imagine for what had happened if a few seconds earlier, the wife of the head of the British Mission was caught crawling and was shot in the posterior! It was [inaudible] incident there.

Talking about Oppenheimer. Then I used to meet him every other week at the coordinating council. You know about the coordinating council? This is the place where usually only the heads of the sections used to meet. The British team did not have a section, so they gave them a special status. Not all of us had one.

Sherwin: Did [Klaus] Fuchs go to that first meeting?

Rotblat: No, Fuchs did not. But the British people were Chadwick and [Otto] Frisch and myself at the beginning. And then [Rudolf] Peierls joined us also, and Philip Moon. Then one other, yes of course, [James] Tuck came in subsequently and [William] Penney. These are the people who have participated on the British team.

Then of course one could see the genius of Oppenheimer. This was really place that he shone, because he would usually ask somebody to present a case and he would summarize it, and we were waiting for his summary to understand really what was going on.

Sherwin: Do you remember a specific case where you could describe the details of this kind of performance?

Rotblat: I am trying to remember, just because there are so many that came up. Well, some of these things were concerned, for example, with the implosion. It was a very difficult aspect of it. [George] Kistiakowsky would present it with his Russian accent, and Oppenheimer would really summarize it.

Sherwin: I know it was quite a time between when [Seth] Neddermayer sort of thought about the idea, and then figuring out the details. In your recollection, what were the main steps to the perfection of the—?

Rotblat: The main problem was the lens. This was the main issue, whether you get symmetrical lenses was the main issue. Of course, if you didn’t get symmetrical, then the whole thing will blow away and nothing would happen.

Sherwin: Right. So it was an explosive engineering problem?

Rotblat: Very much so, yes.

Sherwin: That is certainly about as far away from Oppenheimer’s specialty—

Rotblat: That is right, and mine too. This is not my field at all. But these are the sort of people, like Kistiakowsky and Penney, G. I. Taylor, who came for a visit from Britain and he was explaining this. In fact, he was the one who wrote in telling [inaudible]. I mean, this is why I say I appreciate Oppenheimer’s summing up, because it made it so clear to me what it was about.

Sherwin: Yeah. That was the great strength of his both the scientific and then administrative.

Rotblat: As the director of a large institution.

Sherwin: Yes.

Rotblat: He certainly was considered to be a semi-god. This is the information which I had in two articles.

Sherwin: Except [Edward] Teller, of course.

Rotblat: Teller was always a difficult person. I knew quite a bit about Teller’s work. Of course, his office was next to mine. Apart from working in the L Division, we also had our offices in the Tech Area. And he and Ulam, Stan Ulam, worked on this project. Stan Ulam being also of Polish origin, like myself, so we became rather friendly, we used to talk a bit. So I knew quite a bit about the work on the Super. But I cannot recollect Teller making any sort of important progress on this at the coordinating council.

Sherwin: Well, I do not think that there was progress. I think as late as 1948, ’49, every time he made a progress report to the Interim Committee, as [Lee] DuBridge once told me, it looked worse and worse, the prospect of whatever design he came in with actually working. Did you have any sense of the relationship between Oppenheimer and Teller?

Rotblat: No. Well, hint. From my talks with Ulam, indirectly rather than directly. As I said, I cannot recollect even Teller making any comments at the coordinating council, it did not come up. And of course at the other meetings I mentioned, it also did not come up.

Privately there would be socials sometimes, in some of the evenings. I had been invited to the Teller’s and to [Hans] Bethe’s, and so on. I used to go out on excursions with them on Sundays, but I do not think that these matters would come out in my presence. I do not think I can really add anything about it.

Sherwin: You said that you had dinner at Oppenheimer’s house occasionally?

Rotblat: I used to come to parties. Only once for dinner.

Sherwin: Okay. Do you remember the occasion?

Rotblat: Of the dinner?

Sherwin: Yeah.

Rotblat: No, I think somebody else was there. I cannot even remember who it was. Mostly it was to introduce me to Kitty [Oppenheimer] and to talk a little bit about—of course I was, remember, the only foreigner, apart from the British. 

Sherwin: At that time, were you still a Polish citizen?

Rotblat: Yes, exactly. You know the story about my citizenship?

Sherwin: I do not think so.

Rotblat: I didn’t describe this in the article, no. It is rather funny.

My intention when I came from Poland for one year to do research. 1939. I worked there for one year. Although we knew the war was going to come up [inaudible] for quite a while, we could not just—we had to live our lives. That is why I accepted this invitation to Chadwick to come there for one year. And I was particularly interested in the cyclotron, because I was hoping to build a cyclotron in Poland afterwards.

So when the war broke out and my stay was prolonged for a few years, I still intended to go back to Poland. Indeed, when I went to Los Alamos, I took everything with me, all my belongings. Of course then my intention was to go directly from the States back to Poland.

In 1943, I suddenly received a visit from a policeman in my digs in Liverpool. He began to ask me some personal data. So I said, “I had given all this information. Why do I need to do it again?”

“Oh, we have to process your naturalization papers.”

I said, “I have not applied for British citizenship.”

He said, “Well, I do not know. I was told to do this. I am doing my job.”

So then I went to Chadwick to ask him what is this all about. It was a complete surprise out of the blue that I had to become a British citizen. So Chadwick then explained to me the reason, which is a very curious reason. He said that the agreement in Quebec between Roosevelt and Churchill on the collaboration for the British team stipulated that only British subjects would take part. The reason why it was stipulated by the Americans was because they had great trust in the British intelligence, the MI-5.

Sherwin: Yeah.

Rotblat: Before giving anybody British citizenship they would have an inquiry and vet the people politically, so that undesirables would not get through. This is why they made that stipulation. Here they would be giving instant citizenship to [inaudible.] So this is how he explained it to me and the reason why. Of course, there were a few foreigners, Frisch, Peierls, and Fuchs. So all these people became overnight citizens.

I refused, because I said my intention was to go back to Poland and I do not want to change. I said, “I like life in England, but still I want to go back to Poland.” 

It took me a while to realize that I wouldn’t be able to join them, as it were. [Inaudible] They left in 1943, and I stayed behind. Two weeks later, two weeks later I received a cable from Chadwick to pack my bags and follow them. Because as soon as he came to Washington, he talked to Leslie Groves about me, and Groves agreed to make an exception in my case and I could come. I was the only one who was actually a Polish citizen.

Sherwin: So it actually not just an Anglo-American project, but it was an Anglo-American-Polish project!

Rotblat: In this sense. It became like this. And at that time, Poland was very much in the news, as it is now. Therefore, certain people wanted to find out a little bit of what is going on. This is why—I imagine for other reasons, too—why I was invited to these social events.

Sherwin: What was your impression of Kitty?

Rotblat: I must say that I was not very favorably impressed by her. She seemed very much aloof. I don’t know, maybe she was drunk at the time. I do not know. It did not occur to me and I never want to attribute the wrong motives to people unless I know it for certain. But during the conversation, she hardly took part. She kept going out. The baby was crying next door, and she kept going out there. But really the conversation was with Oppie and other person who was there, and very little with her.

I met her again at some of these social parties, but hardly ever did I get close to her. She seemed to me to be [inaudible] aloof. I did not realize at the time that she was involved in the Communist Party. I did not learn about it until afterwards.

Sherwin: At the time, of course, she wasn’t.

Rotblat: At our first meeting, she didn’t give too many personal things. On the contrary, she was a haughty person to me, she could be so superior. This is the impression which I got—maybe a wrong impression, but this is the impression which I got of her. But I never got to know her.  

Sherwin: Now in terms of your decision to leave, which you wrote about in the article, I would like to see if I could coax out of you a little more of the texture of that decision. You said Niels Bohr was very important?

Rotblat: Partly, yes, he is just part of the story. I was becoming more and more unhappy about my participation in the project, even without Niels Bohr, for the simple reason that I had begun to realize when I came to Los Alamos the enormity of the project, how much it requires, the enormous manpower required, and the technological resources, to see how much money went into there. Ignoring what was going on in Oak Ridge, Hanford, and Berkeley. There is this enormous effort for the Americans to make the bomb.

I could see that the war was coming to an end in Europe, and still it did not look like the bomb would be finished. We still had to grapple with basic issues like the implosion technique. But it became clear to me that [it was] very unlikely the Germans would make the bomb. I did not believe that the Germans could really produce something at less cost in this time, taking into account their involvement in the war [inaudible] was going on.

 It became clearer gradually that the Germans are not going to make the bomb. The only reason really why I worked on the bomb was because of the fear of the Germans. This is the only reason. I would never have worked otherwise on this. This is quite simple, and no to be swayed, [inaudible] my motivation for work on the bomb was becoming invalid. But it was fortified by two events—well, not quite events. One was an event. This is the remark made by General Groves, which I described.

Sherwin: Yes, would you describe it again, for the tape recorder?

Rotblat: Yes. At that time, it was March of 1944, I was living with the Chadwicks, and Groves prepared to make a visit to Los Alamos. The notification was he would come to the Chadwicks, because he became very friendly with Chadwick and would have dinner. Therefore, I was being a resident in the house, therefore I was also there.

This struck in my mind, the shock of it. We had been talking of a general sort over dinner on sort of things. It came down to the project. All of a sudden, he said, “You realize, of course, that one purpose of this project is to subdue the Russians.” To me it came as a terrible shock, because to me the whole premise of the project was quite different.

Sherwin: Did somebody say something in response to that, do you recall?

Rotblat: No, nothing at all. I was stunned completely. And Chadwick, he used to say very little in any case. He is a very passive person. We went onto something else. I did not react to it, because I was completely stunned. I mean, at that time really the war was still in the balance, and the Russians really carried the whole ground war at that time, before the second front started. This was March of ’44. Everything depended on how the Russians would be able to overcome [inaudible].

Here I am told that what I am doing here is just helping to subdue the Russians. I never got over this shock. It was something that always stayed with me for the rest of the time at Los Alamos.

Sherwin: Did you mention this to anybody?

Rotblat: No, not immediately. I do not think that I mentioned it to anybody because I felt that this was sort of a private meeting, and I did not think that I should tell to with other people what happened in a sort of private setting. I generally don’t like to talk just for the sake of talking. [Inaudible]

Maybe I have mentioned it to one person. One person who I worked with closely was Martin Deutsch. Perhaps you know him?

Sherwin: No.

Rotblat: He is at MIT.

Sherwin: He’s still at MIT?

Rotblat: I think he is still at MIT. I am not sure, I have a feeling that I had mentioned it, because he is the only person about whom I did talk with about some of these matters. Otherwise I did not, not until I came back and I felt that I was free to talk about these matters [inaudible.]

The other thing I mentioned was the conversations with Bohr. He indicated to me that the possibility of an arms race between the United States and the Soviet Union. He had described what the consequences were going to be. This was an eye-opener for me. I had never thought in these terms before. I was single-minded at the time, making the bomb to prevent the Russians from having it was all I—

Sherwin: The Germans?

Rotblat: The Germans, yes. I did not think in the global terms, how it was going to affect the whole strategy in the postwar period.

Sherwin: What you said about your motivation to build the bomb, I think most of the people there would say about their own motivation. That is, they got into the project because of the fear that Germany would build a bomb. Aside from this conversation that you had with Groves, which was unique, it put you in a unique position. Other people also talked to Bohr. Other people also realized that the war was coming to an end. What do you think differentiated you and your decision from others? You talk about your decision to leave. You must have talked about it with Chadwick.

Rotblat: People react to the same series of events in different ways, because what we do is the result of many tiny events which influences us, and therefore makes the differentiation easier. In a large group of people, you are bound to get different reactions. It covers the spectrum. But there’s bound to be somebody who is at one end of the spectrum.

In addition to this as a general observation, I should imagine that the reason why I felt particularly strongly is because of the [inaudible], which I had from the very beginning of the whole idea was also because I felt particularly responsible because I could say that I initiated the work in England, which I did not know about this at the time. This puts me in a special position of special responsibility for it.

It took me months to work out a rationale for my working on the bomb. Because I had thought about it already in 1939, March of 1939, in March when I discovered the emission of neutrons in fission. Immediately, the idea of the possibility of the bomb came to me. But of course, I rejected it. In any case, I had no possibilities at this stage even if I wanted to.

But from the very beginning, I was afraid of the Germans. This sort of kept gnawing me all the time until I moved to England and I did other things. This was still there all the time. Gradually, the fear became stronger as the war became more realistic. Also, I had read something in an article, as I mentioned in this paper, German [inaudible] inNaturwissenschaften, in which at the end he mentioned the possibility of military applications. I could see it from this evidence that some people had been thinking along these lines.

So I had to work out some rationale, and I gradually worked out this rationale of deterrence. But even then, I was not convinced that I should really work. So this was a tumor which had been growing. Difficult to imagine this sort of torture, the mental torture of myself whether I should do something about it or not.

I kept saying, “No, this is not my field, and I am not up to that sort of thing.” Then I had the chance to go to Poland in August ’39 for personal reasons, and I took the opportunity to talk to my professor in Poland.

Sherwin: What was his name?

Rotblat: Wertenstein.

Sherwin: How do you spell that?

Rotblat: W-E-R-T-E-N-S-T-E-I-N.

Sherwin: What is his first name?

Rotblat: Ludwik, L-U-D-W-I-K. He was an extremely good physicist, a very good person and man, and we became very friendly with him and really close to him.

Sherwin: Did he survive the war?

Rotblat: No. Strangely enough, he almost survived the war. In ’44 he managed to escape to Budapest in Hungary. He was hiding there, and then he became sick and he went to get some medicine. He went across the bridge, the Danube. The Russians then began to shell Budapest and then a shot hit him. It was such a shame, he had managed almost to the end of the war. It was a terrible tragedy.

Sherwin: So you spoke to him?

Rotblat: So I spoke to him about this. It was the summertime in August, he was in his dacha, his country house, living there. I went to visit him, and I talked to him about this. At that time, I had my calculations.

Sherwin: This being the possibility of a nuclear bomb?

Rotblat: Exactly, that this could be a possibility.

Sherwin: Right.

Rotblat: I showed him my rough calculations. He looked at them and he pondered a little bit and he said, “Is this something which requires more scrutiny, but for the moment I cannot see anything wrong with your general idea about the possibility.”

Then I talked to him about my mental torture about whether I should go to work on it or not. He sympathized with me, but he said, “It is must be your own conscious.” He would not advise me. I asked him for advice. Of course, now I can see I should not have asked him for advice something which would burden another person. He said, however, that he himself would not work. You see how I got my ideas from people about what I call this sort of responsibility of scientists, through my work with him.

So I left on my own. Then I came back on almost the last train to go through Germany, from Poland to Germany. Two days after I reached Liverpool, war broke out. It was the 1st of September. It was August when I came back, and the 1st of September, war broke out. It was panic, of course. It hit me in many ways. First I thought, “I must try to help Poland.”

So I tried to hitchhike from Liverpool to England, because I had no money at all, to the Polish Embassy and see if I can somehow I can go back. [Inaudible] But I found the Polish Embassy is complete chaos. They asked me for advice on what they should do. So that was completely useless. Then in a week or two, Poland was overrun.

So this was the final thing which clinched it. I could see now that the German might is real indeed, and if they could overrun Poland within a short time, then what was going to stop them? At that time, the Russians were their allies after the pact with Stalin.

Sherwin: Right.

Rotblat: The Ribbentrop and Molotov. 

Sherwin: Yeah.

Rotblat: And of course two days later Britain declared war.

Sherwin: Right.

Rotblat: There was not much [inaudible] in this country, in Britain, right before the war. At the last minute, [inaudible] gone to war. Then at five minutes to eleven on a Sunday, the 3rdof September, I was in the lab. I came back to listen to [Neville] Chamberlain’s broadcast. People were happy, “Oh no, we are not going to war. Oh no, we’ll never go to war.” Then came the broadcast, and he announced that we are at war.

I could not see that Britain would really—I did not foresee Dunkirk. I thought they were trying to make peace, and Germany would then be really supreme. So this was the thing which convinced me that I must overcome my scruples, and then decide to go. But I could not go immediately, because Chadwick was away at the time, fishing somewhere in northern Norway. I had to wait until he came back and I settled my immediate financial affairs.

Then I went to him and suggested to him my plan about work on the bomb. At that time, I said I did not know then what else I think about it. Therefore, I could see the initiative was mine. I could really start it. Certainly I was at that time, the first to start it. Maybe because of this that I felt an extra responsibility, a little bit more than the other people who were recruited by others who [inaudible]. I tried to explain [inaudible] your question as well as I can.

Sherwin: Sure. No, this is very interesting. Were you involved with Frisch and Peierls?

Rotblat: Yes, afterwards. You see, Chadwick was really a person who, if one needed three words, he would use one. And [inaudible] to talk to. He was a very, very close person in personal relations. For some reason he took to me from the very beginning. As soon as I arrived to Liverpool, somehow he became friendly.

I did not realize that I was the only person in the whole department who had ever been to his house in Liverpool. I do not know why he just took to me, but even so he will never [inaudible.] When I put the project to him, he did not mention to me that anybody else was working or not. For a long time, I did not know. I started to work just on my own.

Sherwin: Yeah.

Rotblat: Afterwards, then Frisch and Peierls, independently, in Birmingham.

Sherwin: Right.

Rotblat: This was in 1940.

Sherwin: Right.

Rotblat: Then we began to get to together in the initial MAUD Committee. Then of course it was decided that Frisch being an experimentalist, should come to Liverpool, because most of the experimental work was done at Liverpool. And this is where I got together with Frisch, and we worked very close.

Sherwin: I am going to give you a copy of my book, which I wrote on the Manhattan Project, and I can see that I embarrassingly have missed some vital information.

Rotblat: But it was my fault, because I did not want to talk about this for a long time. I just did not feel that I [inaudible] my life, you know, to talk about it.

Sherwin: Yeah.

Rotblat: It was only when the editors of the Bulletin [of Atomic Scientists] asked me specifically. And in fact John Holdren, one of the Board of Editors, he put some pressure onto me. I asked him to do something else, and he said, “Yes, if you write this article.”

Sherwin: Uh-huh.

Rotblat: So I wrote this article.

Sherwin: Now all of this brings us back to 1945, with a lot more understanding of what was happening. And there are two events here. One is the discovery by the Alsos group that the Germans have not gotten anywhere, and that is in December. But Los Alamos does not hear about that until much later. And then there is of course the German surrender on May 8th. When do you start in your head coming to the conclusion that you are going to go? 

Rotblat: Well, as I said, gradually sort of for several months of 1944, I became increasingly unhappy about my being there, because I could see that the purpose is not really valid. But I still could not be quite sure.

At that time, Chadwick had left Los Alamos, he had already left I think in June, to move to Washington. He became the head of the British Mission in Washington. But he used to come from time to time, he would come to Los Alamos. In October ’44, he came to Los Alamos and as usual we had a session with him. And then he told me that there was now intelligence information that the Germans are not working on the bomb.

Sherwin: In October of ’44?

Rotblat: Yes.

Sherwin: That was even before the Alsos Mission.

Rotblat: Yes, it must have been some information. 

Sherwin: Are you sure about that date?

Rotblat: Of course I am sure.

Sherwin: No, I have to ask, simply because that is something that I did not know, that people knew by October ’44 that the Germans were not working on it.

Rotblat: I think it was the year before that, but I am not certain. The Germans had not been working for some time.

Sherwin: Right.

Rotblat: They never really put themselves properly to it.

Sherwin: Right, but there was no real knowledge of that until the Alsos Mission. 

Rotblat: Well, that mission gave direct evidence.

Sherwin: That’s right.

Rotblat: But intelligence had something before.

Sherwin: Well, it sort of went both ways. I mean, I remember Philip Morrison telling me that up until quite late, he was busy doing calculations trying to figure out whether supplies were being moved here and there.

Rotblat: Yes, they were aware of these. I remember Chadwick in the previous visit to Los Alamos telling me that the Germans are putting up some strange sort of constructions on the coast of Normandy and the Belgian coast.

Sherwin: Was that [inaudible] and the D-Day?

Rotblat: Well we did not know at the time it was [inaudible.]

Sherwin: Right.

Rotblat: He told me that this is what intelligence is showing, that they are putting up these—and the suspicion is that the Germans have prepared a large amount of radioactive materials in their reactors. They’re going to send shells over with radioactive materials into London, to poison London. He asked me to look into this and to see whether it is feasible that they really could cause radioactive damage in London.

So you see with this information, he used to get very high topics in intelligence. He would know these things before other people would know. I then made the calculations, I worked at it, and it seemed to me completely unrealistic, that they could not make really enough material to cause radioactive damage.

I will give you this example that I was in touch with Chadwick about the various events. Of course, other people did not have this information, but you are asking if I am sure about this.

Sherwin: Yes.

Rotblat: I am sure because this was the date. After this discussion, then I decided that I am going to leave. In fact, this is at the point which finally decide for me. I could not forget this.

Sherwin: Right. Okay. I believe you, I just wanted to double-check.

So you had to go to Oppenheimer at some point, then?

Rotblat: No, not at all. Legally, I did not have to go to Oppenheimer, because I was a member of the British team and I was responsible to Chadwick, not to Oppenheimer.

Sherwin: But didn’t you go to Oppenheimer?

Rotblat: Well, yes. I said goodbye to him. But this was after all of the dramatic events, which occurred in between. I told Chadwick about this, and he was not happy about it, clearly. He said, “This is going to cause a great deal of unpleasantness with the Americans,” and I should not leave. It reminded me of the initial discussion I had when I said I am not going to be going at all because of the citizenship.

I caused him trouble. I said [inaudible.] But I told him my reason, although he never agreed with me. Politically, we are not at all on the same wavelengths. We were friendly, and respected each other’s views. So he eventually said, “Yes, and I want you to go and talk to De Silva, because your release has to come from intelligence, you see, and not through Oppenheimer.”

This is when a few days later, he came back and he told me about what De Silva told him about my dossier. They had accumulated an enormous dossier on me, in which they made it out the reason why I decided to go back is because I wanted to go back first to England, then somehow be flown from England across the Polish—Poland was occupied by the Russians [inaudible], drop by parachute, that sort oft thing—all in order to give all the secrets away to the Russians. This is how they gave the reasons why I wanted to go.

They put in some details of that conversation which I had with a young lady in Santa Fe, which could have been really damning. It could have been very bad for me. But fortunately, of course, the conversation was completely wrong; much was a complete invention. But in their zeal, the agent who was listening in, they put in dates and places, but my meetings could put this young lady, who was supposed to be my contact, which I could show directly diaries and other people knowing that it was impossible to have been in these places. I had to indicate it. Then they realized that the whole dossier was just nonsense.

Sherwin: Uh-huh. So they were following you and listening in?

Rotblat: Oh yes, they followed me for months.

Sherwin: Uh-huh. You were dating someone in Santa Fe?

Rotblat: Well, you call it dating, it was not actually dating. No. I was a married man, and I was not dating anybody. It was a long story, but she is really irrelevant to our history here. I was really trying to help somebody, to help a young woman in distress. Very distressed. You see, which I was trying to do. Moreover, I would tell Chadwick each time I went to see the lady.

As far as I am concerned, although formally I committed to that. But here was another thing: since I felt responsible for Chadwick, and he gave me this dispensation, I thought I was all right. I did not realize that all of these stories would come out.

Sherwin: Did you talk to Oppenheimer at all about this?

Rotblat: No, I just went to say goodbye. There was a party given to me. At that stage, I have to mention—although De Silva agreed that the dossier was phony and the accusations against me were completely false, nevertheless, he did not trust me completely, for one thing. He insisted that I must not tell anybody the reason why I wanted to leave.

So Chadwick put another idea, which was partly true, that was that I was very concerned about my wife, whom I had left in Poland. I did not know what was going on for a long time. How can I contact her? Use this.  The official reason given was that I am unhappy about my work, and I am hoping to [inaudible].

Sherwin: Yeah.

Rotblat: This is the official reason, which we gave.

Sherwin: Oh, I see.

Rotblat: But I could not tell the people, to talk about the reason [inaudible] [00:55:38]

Sherwin: I see.

Rotblat: They gave me a party.

Sherwin: Yes. Well, thank you very much.

[End of audio]

Copyright 2005 Martin J. Sherwin. This transcript may not be quoted, reproduced, or redistributed in whole or in part by any means except with the written permission of Martin J. Sherwin. Rights granted to Atomic Heritage Foundation.