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Hans Bethe's Statement to the FBI on Klaus Fuchs

February 14, 1950
On January 27, 1950 Klaus Fuchs, a British Scientist who had worked on the atomic bomb at Los Alamos during the war, confessed to being a Soviet spy. On March 1, 1950 he was tried and found guilty at the Old Bailey in London.

Dr. HANS BETHE, Nuclear Laboratory, Cornell University, Ithaca, NY., advised he has known subject since 1934, when he met him at the University of Bristol in England. Subject worked under his supervision at Los Alamos in the Theoretical Division, from 1944 to 1946. Subject visited Dr. BETHE in Schenectady, N.Y., in the summer of 1946, and in Ithaca, N.Y., in the spring of 1943 or 1949. Dr. BETHE visited the subject in England (Harwell), during the summer of 1948. Dr. BETHE advised he never had any reason to suspect the subject of espionage, and further that subject never seemed to be pro-Russian. To his knowledge, FUCHS never attempted to elicit any confidential information from him. He described him as extremely brilliant and as one of the top men in the world on atomic energy. Dr. BETHE furnished the names of subject's know contacts in the United States.

Bureau teletype to Albany, 2/14/50


Dr. HANS BETHE, Nuclear Laboratory, Cornell University, advised that he has been a close associate and friend of subject, and that he considers him one of the world's leading atomic scientists. He first met FUCHS at the University of Bristol, Bristol England, in 1934. FUCHS was a graduate student, and BETHE was a research assistant.

Dr. BETHE stated that they did not become too well acquainted at this time, and that this period of association lasted for only half a year. He learned that FUCHS had left Germany for political reasons, but did not learn the details of his leaving. Dr. BETHE remembered that he had thought this to be quite commendable at the time. Subject impressed him as a very brilliant and quiet, and unassuming young man. Dr. BETHE recalled that many of the students and research assistants would often gather for political discussions and that the majority seemed to be very far to the left. However, subject never entered into these discussions and did not appear to have any political learnings. Further, he did not appear to have any particular friends or associates.

Dr. BETHE stated that after leaving England, he did not see subject for quite some time. He believed, however, that he perhaps contacted him professionally in 1936 and 1938, when he (BETHE) made visits to ENGLAND.

In 1944, Dr. BETHE was in charge of the Theoretical Division at the Los Alamos Project. This division performed the calculations ahead of time as to how the bomb was to be made and assembled and how it would work. As a result of the Quebec Agreement, England furnished several top scientists to work in this division. They were about twelve in number, and Dr. BETHE stated that he does not believe that the bomb would have been completed as soon as it was without their assistance. Dr. BETHE personally requested that Dr. RUDOLPH PEIERLS, of the University of Birmingham, be assigned to the project. Dr. PEIERLS accepted with the stipulation that he bring with him two of his best collaborators (Dr. FUCHS and a research man named SKYRME). They joined the laboratory, and with some ten American scientists, were assigned to the particular task of determining the best way of bringing together parts of materials, so that after assembly there would be more than the "critical mass). Dr. BETHE stated that the name of this group is still classed as restricted information due to the fact that their work was about the most highly confidential work done. As a member of this group, subject was in as vital a position as anyone on the entire project, and had access at all times to all parts of the laboratory and all documents, except perhaps some "top secret" documents. However, Dr. BETHE stated that this did not mean that he could not examine the "top secret" documents which were necessary to his work, upon clearance and permission.

Dr. BETHE advised that subject lived in a dormitory on the project. He had a personal automobile, which he bought second-hand at this time. He had no particular close friends. Subject worked at Los Alamos under the supervision of Dr. BETHE from the summer of 1944, until January, 1946, when BETHE left. FUCHS left during the summer.

In June or July, 1946, subject visited Dr. BETHE at the General Electric Company, Schenectady, New York. He was on his way back to England. Dr. BETHE recalled that their main topic of conversation was of a sad accident that had occurred at Los Alamos, when Dr. SLOTIN was killed by radioactivity when one of the reactors ran away. FUCHS attempted to calculate why such an accident had happened. He did not spend much time at the plant, and did not question Dr. BETHE concerning his work. It was Dr. BETHE's recollection that the subject's sister from Boston, came to Schenectady to meet him. He stated that he did not meet the sister and does not know her name. He believed that subject remained in Schenectady only one day.

Since the above meeting, Dr. BETHE stated that he has seen subject two other times. One occasion was in England, during the summer of 1948, when BETHE spent a day and a half at Harwell. He talked to subject, as well as several other scientists. FUCHS showed him around a bit, and told him something of the theoretical work being done there. BETHE was under orders of the Atomic Energy Commission not to talk of restricted matters, and so the conversation was strictly one-sided. He stated that the subject did not appear to be particularly interested in what was going on in this country.

During the spring of either 1948 or 1949, subject visited Dr. BETHE, at his invitation, at Ithaca, New York. He had come from England to attend Declassification Meetings, which were held in Washington. DR. BETHE advised that he believes that FUCHS stayed one day. Their main topic of conversation was nuclear reactors and declassification. Again Dr. BETHE was under orders not to speak of restricted information, so all conversation was one-sided.

Dr. BETHE stated that during their association, he never had any reason to suspect subject of espionage or even to consider him to be pro-Russian. FUCHS-always remained aloof from political discussions. He was always very quiet and reserved, and appeared to live for his work. He never spoke of his life in Germany, or much concerning his family. He did mention his father from time to time. Dr. BETHE stated that he had always understood from conversation with his English associates that the elder FUCHS was a fine old gentleman. Dr. BETHE advised that to his knowledge, FUCHS never attempted to elicit any confidential information from any of his co-workers. But, as Dr. BETHE put it, subject knew as much restricted information as anyone and really did not have to do much questioning in order to know just what was going on. Dr. Bethe stated that subject's arrest was a complete surprise to him, and he now feels that he does not know whom he can ever trust since he had always regarded FUCHS as absolutely loyal and trustworthy.

Based on his own personal knowledge, Dr. BETHE furnished the following background data concerning subject. He immigrated from Germany in 1933 or 1934 to escape Nazi oppression. He was a student at Bristol University, Bristol, England, from 1934 to 1935, taking his Doctor of Philosophy Degree there. He remained at Bristol as an instructor until about 1940, when he was interned as a German national and taken to Canada. His work, while at Bristol, was chiefly concerned with the theory of solids.

Subject was returned to England and released in 1942, when he joined the research staff of Dr. PEIERLS at the University of Birmingham. His work with PEIERLS was concerned with atomic energy, particularly in the separation of uranium isotopes by diffusion, which according to Dr. BETHE, is the basis of the Oak Ridge Project. When the development of Oak Ridge was being considered, Dr. PEIERLS was asked to come to this country as a consultant. He brought FUCHS with him, and they planned many of the installations there, particularly the diffusion plant. This work took place in New York in 1943.

In 1944, PEIERLS and FUCHS went to Los Alamos, where FUCHS remained until about July, 1946, when he returned to England. Since that time, he has been employed at Harwell.

Dr. BETHE stated that he knew of no relatives of the subject in this country, other than his sister in Boston. He listed the following persons as associates of the subject in this country.

Dr. VICTOR WEISSKOPF - Physics Department, Massachusetts Institute of Technology, Boston, Mass.

Dr. ROBERT MARSHAK - Physics Department, University of Rochester, Rochester, New York.

Dr. EDWARD TELLER - Los Alamos Project

Dr. CARLSON MARK - Los Alamos Project

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