The following is a letter on file at the British Public Record Office in London, class number AB1 639. It is marked "secret". It was declassified during the 1980s, but so far as I can make out did not catch the eye of Fuchs's biographers or other intelligence scholars. It is written on the headed paper of the British Supply Council in North America, Washington.
I am grateful for the assistance of Brian Cathcart (author of Test of Greatness: Britain's Struggle for the Atom Bomb) who provided this document to me.
For a brief discussion of Fuchs' see this article.
Last changed 22 September 1998
July 14, 1944
I have now had talks with both Kearton and Fuchs about the future of the New York section and in particular about their own positions. As a result, Kearton will approach Keith and Benedict with the object of getting a letter by one or both of them to Groves to say that the services of Fuchs and Skyrme are no longer required. It is possible that this matter was raised by Groves on a visit to New York earlier in the week, but I have had no news from him so far.
The position of Skyrme is quite clear. Bethe or Oppenheimer should write to Groves asking for his services in Y. Groves has provisionally agreed and there should be little delay over his transfer.
Fuchs' future is not so clear. I gave you the gist of a cable from Akers in my letter of July 11. I did not agree with the suggestion made in this cable that Fuchs was not required in England, but I wished to discuss the question with Kearton before I made up my mind. Kearton was very strongly of the opinion that Fuchs was quite necessary in England if work on any kind of diffusion plant is to continue...
I have now had a talk with Fuchs himself. He feels that he has a special contribution to make in England, whereas in Y he would be one of a number and can make no really significant difference to the work
I agree completely with these views of Kearton and Fuchs, and I feel sure you also agree at least in principle.
I come now to the point of this letter It would put me in a very awkward position if a request for Fuchs' services in Y were to be sent to Groves. If Groves were to agree I also should have to consent, for the consequences of refusing, on the grounds that he was needed in England for work which can have no significance for the war, might be quite serious. It would certainly cause great resentment in some quarters and our relations with the U.S. on this project would be impaired. I should attempt to justify his return as being useful for the New York project, for after his experience here he could interpret their requests and help to direct U.K. work into directions of immediate interest to them. This argument would of course not be valid if a low-separation diffucison plant were to be started in England.
I therefore do not want Bethe to ask for Fuchs. Further than that, I want Bethe to say that Fuchs would not be specially useful in Y, if Groves asks if they want him, as he may. This means some tactful work on your part and I hope you will be able to do what is necessary by suggestion rather than direct action.
I have prepared the ground here and I think the matter can be arranged. I have stated that Fuchs could be useful in Y but that his special qualifications are not on the nuclear side but on the diffusion plant.
Until I know something of what is happening in London I want to keep the New York psotion as fluid as possible.
By Brian Cathcart
This document is of interest because it shows that in the summer of 1944 Klaus Fuchs was reluctant to go to Los Alamos and was a party to British manoeuvres to prevent his transfer and ensure that he spent the rest of the war in England. Given that his assignment at Los Alamos was to prove of historic importance, providing the Soviet Union with a fund of information both on the implosion bomb and on early hydrogen bomb thinking, this is certainly ironic. It also raises some interesting questions about Fuchs's character, motivation and state of mind.
The context is this. Fuchs was a member of a small British team working in New York to assist the American gaseous diffusion programme. The other members were Rudolf Peierls and Tony Skyrme, both close associates from Birmingham University, Nicholas Kurti from Oxford, and an engineer called Kearton, who was from ICI's base at Billingham in England.
The letter is written by James Chadwick, who was then head of the British atomic mission in the United States, to Peierls, who had by this time arrived at Los Alamos, drafted in at Oppenheimer's request to take Edward Teller's place as a group leader on implosion. It reflects, very strongly, Chadwick's commitment to maintaining some kind of atomic programme in Britain, a commitment he was soon to abandon.
The critical passage comes when we find Fuchs agreeing that he would be more useful in England than at "Y", which is Los Alamos. Why would he have taken such a view?
Let us assume he was being honest and above board. It is a fact that at this stage Fuchs was unaware of the implosion design, of the weapons potential of plutonium or of the existence of the Hanford piles, and in that light he might have been justified in assuming that no really exciting or difficult physical problems remained in bomb design. He may have been caught up in the gaseous diffusion work and eager to push it forward in England.
Remember, however, that he was spying. He had met his espionage contact, Harry Gold, several times in the few months before this in New York and handed over information relating mainly to gaseous diffusion. It is hard to believe, although not absolutely inconceivable, that he thought Los Alamos would be such a nuts-and-bolts place that it would not be scientifically worthwhile going there to spy. Perhaps he thought that if he went there he would not be able to get information out. Or perhaps -- and this is the really juicy possibility -- he felt at that moment that he did not want to go on spying, that he had done enough.
This is more likely than it may seem. Fuchs was always ambivalent about spying. Initially, according to his 1950 confession, he had intended only to alert the Soviet Union to the possibility of a bomb. Then he was persuaded to give more, but he insisted at first that it would only be his own work. Later he passed on much more. Eventually, in 1949, he spontaneously decided to give up spying without informing or warning his KGB masters.
At roughly the time of this letter he informed Harry Gold that he might be posted to New Mexico (there was a muddle here: Gold heard "Mexico"). Then he was sent, and either did not have time or did not bother to let Gold know. He took the precaution, en route, of calling his sister in Cambridge, Mass, to tell her he was going to work in New Mexico but would try to visit her in due course. Whether he meant this to reach the KGB is not absolutely clear, but he knew that it might, and it did. That was not until November, however, and it was not until the following February that he visited his sister and once again made direct contact with Gold.
Why Fuchs was sent to Los Alamos when the British (and he) wanted him in Britain is not clear either, at least to me. Peierls wrote to London that it had been a "difficult" decision. It was certainly a fateful one. Fuchs became an important member of the team there, and also learned an enormous amount which he was able to pass on, not only to the Soviet Union, but in the post-war McMahon Act years, to the British atomic weapons programme.