Fourth Interim Meeting

Thursday, 31 May 1945

Thursday, 31 MAY 1945, 10:00 A.M. to 1:15 P.M./2:15 P.M. to 4:15 P.M.


  • Secretary Henry L. Stimson, Chairman
  • Hon. Ralph A. Bard
  • Dr. Vannevar Bush
  • Hon. James F. Byrnes
  • Hon. William L. Clayton
  • Dr. Karl T. Compton
  • Dr. James B. Conant
  • Mr. George L. Harrison


  • Dr. J. Robert Oppenheimer
  • Dr. Enrico Fermi
  • Dr. Arthur H. Compton
  • Dr. E.O. Lawrence


  • General George C. Marshall
  • Major Gen. Leslie R. Groves
  • Mr. Harvey H. Bundy
  • Mr. Arthur Page


Secretary Stimson explained that the Interim Committee had been appointed by him, with the approval of the President, to make recommendations on temporary war-time controls, public announcements, legislation, and post-war organization. The Secretary praised the brilliant and effective assistance rendered to the project by the country’s scientists and expressed great appreciation to the four scientists present for their significant contributions to the work and their willingness to advise on the many complex problems the Interim Committee faced. He expressed the hope that the scientists would feel completely free to express their views on any phase of the subject.

The Committee had been termed an “Interim Committee” because it was expected that when the project became more widely known, a permanent organization established by Congressional action or treaty arrangements would be necessary.

The Secretary explained that General Marshall shared responsibility with him for making recommendations to the President on this project with particular reference to its military aspects; therefore, it was considered highly desirable that General Marshall be present at this meeting to secure firsthand the views of the scientists.

The Secretary expressed the view shared by General Marshall that this project should not be considered simply in terms of military weapons but as a new relationship of man to the universe. This discovery might be compared to the findings of the Copernican theory and the laws of gravity, but far more critical than these in its effect on the lives of men. While the needs of war have fostered advances in the field to date, it was essential to realize that the implications of the project went far beyond the requirements of the present war. It must be controlled if possible to make it an assurance of future peace rather than a menace to civilization.

The Secretary suggested that he hoped to have the following questions discussed during the meeting:

  1. Future military weapons
  2. Future international competition
  3. Future research
  4. Future controls
  5. Future developments, particularly non-military


As a technical background for the discussions, Dr. A. H. Compton explained the various stages of development. The first stage involved the separation of uranium 235. The second stage involved using “breeder” piles to produce enriched materials from which plutonium or new uranium could be obtained. The first stage was used to create material bombs with a tremendous increase in explosive power over those now in production. Production of enriched materials was now on the order of pounds or hundreds of pounds, and it was contemplated that the scale of operations could be expanded sufficiently to produce many tons. While bombs made from the products of the second stage had not yet been proven in the actual process, such bombs were considered a scientific certainty. It was estimated that from January 1946, it would take one and one-half years to confirm this second stage, given specific technical and metallurgical difficulties, that it would take three years to get plutonium in volume, and that it would take six years for any competitor to catch up with us.

Dr. Fermi estimated that approximately twenty pounds of enriched material would be needed to research current engineering problems and that one-half to one ton would be needed for research on the second stage.

In response to the Secretary’s question, Dr. A. H. Compton stated that the second stage depended on vigorous exploitation of the first stage and would not vitiate the expenditure already made on the present plant.

Dr. Conant mentioned a so-called “third stage” of development in which the “second stage” products would be used simply as a detonator for heavy water. He asked Dr. Oppenheimer to estimate the time factor involved in developing this phase.

Dr. Oppenheimer stated that this was a far more difficult development than the previous stages and estimated that a minimum of three years would be required to reach production. He pointed out that heavy water (hydrogen) was much cheaper than the other materials and could eventually be obtained in far more significant quantities.

Dr. Oppenheimer reviewed the scale of explosive force involved in these several stages. One bomb produced in the first stage was estimated to have an explosive power of 2,000 – 20,000 tons of TNT. The actual blast effect would be accurately measured when the test was made. In the second stage, the explosive force was estimated to equal 50,000 – 100,000 tons of TNT. It was considered possible that a bomb developed from the third stage might produce an explosive power equal to 10,000,000 – 100,000,000 tons of TNT.


Dr. Lawrence expressed his great appreciation for the fact that the leaders of the Government had been willing to take the chances inherent in developing this program. He said that if the United States were to stay ahead in this field, it was imperative that we knew more and did more than any other country. He felt that research had to go on unceasingly. There were many unexplored possibilities in terms of new methods and new materials beyond thorium and uranium. All heavy elements held the potential for exploitation in this field. He thought it might be possible one day to secure our energy from terrestrial sources rather than the sun. Dr. Lawrence pointed out that there was no real doubt about the soundness of the program. Any failures that had occurred or would occur in the future were nothing more than temporary setbacks, and there was every reason to believe such setbacks would be quickly overcome.

Dr. Lawrence recommended that a program of plant expansion be vigorously pursued, and at the same time, a sizable stockpile of bombs and material should be built up. For security reasons, built plants should be widely scattered throughout the country. Every effort should be made to encourage industrial application and development. This nation could stay out in front by vigorously pursuing the necessary plant expansion and fundamental research and securing adequate government support. With this view, Dr. A. H. Compton expressed complete agreement.

Dr. Karl T. Compton, summarizing the views expressed above, suggested the following program:

  1. Expand production under the first stage to produce bombs for stockpile and to furnish material for research
  2. Intensify “second stage” research
  3. Build necessary “second stage” pilot plants
  4. Produce the new product

Dr. Oppenheimer pointed out that one of the complex problems in guiding a future domestic program would be allocating materials between different uses. Dr. Karl T. Compton added that every effort should be made to encourage industrial progress to strengthen our research program.

The Secretary summarized the views of the group concerning our domestic program as follows:

  1. Keep our industrial plant intact
  2. Build up sizable stockpiles of material for military use and industrial and technical use
  3. Open the door to industrial development


Dr. Oppenheimer felt that the work being done under war pressure was plucking the fruits of earlier research. To exploit more fully the potentialities of this field, a more leisurely and more normal research situation should be established. Dr. Oppenheimer strongly urged that the present staff should be released to return to their universities and research laboratories to explore the many ramifications of this field, to avoid the sterility of the current orientation to specific problems only, and to develop cheaper and simpler production methods. Dr. Bush expressed the view that while it was imperative in wartime to concentrate on particular issues, such as narrowing the field in peacetime was utterly wrong. He agreed with Dr. Oppenheimer that only a nucleus of the present staff should be retained and that as many as possible should be released for broader and more accessible inquiry. Drs. A. H. Compton and Fermi reinforced this view by emphasizing that we could only be sure of the tremendous possibilities in this field once thorough fundamental research could be brought to bear.


The Secretary inquired what other potentialities beyond purely military uses might be exploited. In reply, Dr. Oppenheimer pointed out that the immediate concern had been to shorten the war. The research that led to this development had only opened the door to future discoveries. Fundamental knowledge of this subject was so widespread worldwide that early steps should be taken to make our actions known to the world. He thought it might be wise for the United States to offer the world a free interchange of information, particularly on developing peacetime uses. The primary goal of all endeavors in the field should be the enlargement of human welfare. If we were to offer to exchange information before the bomb was used, our moral position would be significantly strengthened.

The Secretary stated that understanding the nonmilitary potentialities was a necessary background to considering the interchange of information and international cooperation. He referred to the Bush-Conant memorandum, which stressed science’s role in securing a policy of self-restraint. This memorandum recommended that in any international organization which might be established, complete scientific freedom should be provided for, and the right of inspection should be given to a global control body. The Secretary asked what kind of inspection might be effective and what would be the position of democratic governments against totalitarian regimes under such a program of international control coupled with scientific freedom. The Secretary said that he felt that the democratic countries had fared pretty well in this war. Dr. Bush endorsed this view vigorously, pointing out that our advantage over totalitarian states had been tremendous. The evidence from Germany revealed that she needed to catch up in the technology of this field and other scientific areas. He said our huge advantage stemmed from our teamwork system and free information interchange. We had won and would continue to succeed in any competitive scientific and technological race. He expressed some doubt, however, of our ability to remain ahead permanently if we were to turn over the results of our research entirely to the Russians under free competition with no reciprocal exchange. Dr. Karl T. Compton felt that we would hold our advantage, at least to the extent of the construction lag, but, in any event, he thought that secrets of this nature could not be successfully kept for any period and that we could safely share our knowledge and remain ahead.

Dr. A. H. Compton stated that the killer applications of these discoveries were more accessible to control than constructive ones. He referred to the nucleonics prospectus prepared some time ago, which indicated other potential uses in such fields as naval propulsion, health, chemistry, and industrial development. He pointed out that Faraday’s hopes and predictions in the area of electro-dynamics were realized by Edison only after the lapse of several decades. Such a lag in this field with as yet uncharted possibilities seemed likely. He stressed the impossibility of keeping technological advances secret, as witnessed in the industry experience. The fundamental knowledge in this field was known in many countries, and a policy of restraint on the nationalization of scientific ideas could not work. Scientists would lose out on many developments if they kept abreast of advances worldwide.

Dr. Conant felt that international control in this field would require the power of inspection and that international arrangements among scientists would strengthen this power. Dr. Oppenheimer expressed doubts concerning the possibility of knowing what was going on in this field in Russia but expressed the hope that the fraternity of interest among scientists would aid in the solution.

General Marshall cautioned to put less faith in the effectiveness of the inspection proposal. Mr. Clayton also expressed considerable doubt on this point.


In considering the problem of controls and international collaboration, the question of paramount concern was the attitude of Russia. Dr. Oppenheimer pointed out that Russia had always been very friendly to science and suggested that we open this subject with them tentatively and in the most general terms without giving them any details of our productive effort. He thought a great national effort had been put into this project and expressed hope for cooperation with them. He felt strongly that we should not prejudge the Russian attitude.

At this point, General Marshall discussed the story of charges and counter-charges typical of our relations with the Russians, pointing out that most of these allegations have proven unfounded. The seemingly uncooperative attitude of Russia in military matters stemmed from the necessity of maintaining security. He said that he had accepted this reason for their attitude in his dealings with the Russians and had acted accordingly. Regarding the post-war situation and in matters other than purely military, he felt he was in no position to express a view. In this field, he was inclined to favor the building up of a combination among like-minded powers, thereby forcing Russia to fall in line with the very force of this coalition. General Marshall was sure that we needed to have no fear that the Russians would disclose this information to the Japanese if they knew about our project. He asked whether inviting two prominent Russian scientists to witness the test might be desirable.

Mr. Byrnes feared that if the information were given to the Russians, even in general terms, Stalin would ask to be brought into the partnership. He felt this to be particularly likely given our commitments and pledges of cooperation with the British. In this connection, Dr. Bush pointed out that even the British still need our plant blueprints. Mr. Byrnes expressed the view, which was generally agreed to by all present, that the most desirable program would be to push ahead as fast as possible in production and research to make sure that we stay on and, at the same time, make every effort to better our political relations with Russia.


Dr. A. H. Compton stressed very strongly the need to maintain ourselves in a position of superiority while at the same time working toward adequate political agreements. He favored freedom of competition and research activity to as great an extent as possible consistent with security and the international situation. Maintaining strict security over this project would result in a certain sterility of research and a genuine competitive disadvantage to the nation. He felt that within the larger field of freedom for research, it would still be possible to maintain tight security of the military aspects of the area. We could only keep our technical advantage over other nations by drawing on the free interchange of scientific investigation and curiosity. He urged the view, expressed earlier by General Marshall that we should secure agreements for cooperation with other like-minded nations and, simultaneously, work toward solidifying our relations with the Russians.

Dr. A. H. Compton recommended that roughly the following program should be adopted for at least a decade:

  1. Freedom of research be developed to the utmost consistent with national security and military necessity.
  2. A combination of democratic powers be established for cooperation in this field.
  3. a collective understanding be reached with Russia.

The meeting adjourned for luncheon at 1:15 P.M. and resumed at 2:15 P.M. All who attended the morning session were present except General Marshall.


One atomic bomb on an arsenal would not be much different from the effect caused by any Air Corps strike of present dimensions. However, Dr. Oppenheimer stated that the visual impact of an atomic bombing would be tremendous. It would be accompanied by a brilliant luminescence that would rise to 10,000 to 20,000 feet. The neutron effect of the explosion would be dangerous to life for a radius of at least two-thirds of a mile.

After much discussion concerning various types of targets and the effects to be produced, the Secretary expressed the conclusion, on which there was general agreement, that we could not give the Japanese any warning; that we could not concentrate on a civilian area; but that we should seek to make a profound psychological impression on as many inhabitants as possible. At the suggestion of Dr. Conant, the Secretary agreed that the most desirable target would be a vital war plant employing many workers and closely surrounded by workers’ houses.

There was some discussion of the desirability of attempting several strikes simultaneously. Dr. Oppenheimer judged that several strikes would be feasible. General Groves, however, expressed doubt about this proposal and pointed out the following objections: (1) We would lose the advantage of gaining additional knowledge concerning the weapon at each successive bombing; (2) such a program would require a rush job on the part of those assembling the bombs and might, therefore, be ineffective; (3) the effect would not be sufficiently distinct from our regular Air Force bombing program.


General Groves stated that the program had been plagued since its inception by the presence of sure scientists of doubtful discretion and uncertain loyalty. It was agreed that everything could only be done about dismissing these men after the bomb had been used or, at best, after the test had been made. After some publicity concerning the weapon was out, steps should be taken to sever these scientists from the program and to proceed with a general weeding out of personnel no longer needed.


Dr. A. H. Compton briefly outlined the Chicago program’s nature and size. In line with directives from General Groves, it was intended to limit the operations at Chicago to those helpful in prosecuting this war. Its activities fell into the following categories:

  1. Aid to the Hanford project on plutonium development
  2. Research on thorium using a pile
  3. Preliminary investigations of the extension of uranium piles
  4. Studies of the health of personnel working with these materials

It was pointed out that programs 3 and 4 above did not bear directly on current war use but comprised only about 20 percent of the work in Chicago. It was considered desirable in terms of future development to continue this work.

It was the consensus of the meeting that the Committee should lean on the recommendations of Drs. Conant and Bush as to what should be done with the Chicago group. Dr. Bush, as seconded by Dr. Conant, recommended that the current programs, including Chicago, should be continued at their present levels until the war’s end; it was agreed that this recommendation should be transmitted to the Secretary of War.


Mr. Harrison stated that the Scientific Panel had been called in at the suggestion of Drs. Bush and Conant and with the heartiest approval of all members of the Committee. It was considered a continuing Panel free to present its views to the Committee at any time. The Committee was particularly anxious to secure from the scientists their ideas of what sort of organization should be established to direct and control this field. The Committee requested the Panel prepare a draft of their views on this subject as speedily as possible. In this connection, Dr. Bush Pointed out that there would be no need to draw up a draft of an organization in this field to consider relationships with the Research Board for National Security. Dr. Karl T. Compton suggested that the organization could be tied in later to the Research Board for National Security through its section on nuclear physics.

The question was raised about what the scientists might tell their people about the Interim Committee and their being called before it. It was agreed that the four scientists should feel free to say to their people that an Interim Committee appointed by the Secretary of War and with the Secretary of War as Chairman had been established to deal with the problems of control, organization, legislation, and publicity. The identity of the members of the Committee should not be divulged. The scientists should be permitted to explain that they had met with this Committee and were free to present their views on any subject phase. The impression should be left with their people that the Government was taking a most active interest in this project.


The next meeting of the Committee was scheduled for Friday, 1 June 1945, at 11:00 A.M. in the office of the Secretary of War. The purpose of this meeting was to secure the views of four representatives from industry.

The meeting adjourned at 4:15 P.M.

2nd Lieutenant, A.U.S.

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