Interim Committee The Interim Committee was a secret high - level group created in May 1945 by United States Secretary of War Henry L . Stimson at the urging of leaders of the Manhattan Project and with the approval of President Harry S . Truman to advise on matters pertaining to nuclear energy . Composed of prominent political , scientific and industrial figures , the Interim Committee had broad terms of reference which included advising the President on wartime controls and the release of information , and making recommendations on post - war controls and policies related to nuclear energy , including legislation . Its first duty was to advise on the manner in which nuclear weapons should be employed against Japan . Later , it advised on legislation for the control and regulation of nuclear energy . Composition . Stimson himself was chairman . The other members were : James F . Byrnes , former US Senator and soon to be Secretary of State , as President Truman ' s personal representative ; Ralph A . Bard , Under Secretary of the Navy ; William L . Clayton , Assistant Secretary of State ; Vannevar Bush , Director of the Office of Scientific Research and Development and president of the Carnegie Institution ; Karl T . Compton , Chief of the Office of Field Service in the Office of Scientific Research and Development and president of Massachusetts Institute of Technology ; James B . Conant , Chairman of the National Defense Research Committee and president of Harvard University ; and George L . Harrison , an assistant to Stimson and president of the New York Life Insurance Company . Harrison chaired the committee when Stimson was absent , but Byrnes , as the President ' s personal representative , was probably its most influential member . The Interim Committee held its first meeting on 9 May 1945 . Stimson began by outlining its broad terms of reference , which included advising the President on wartime controls and the release of information , and making recommendations on post - war controls and policies related to nuclear energy , including legislation . The Interim Committee was not specifically charged with making recommendations on the military use of nuclear weapon s but the composition of the committee and the close relationship between the wartime use of nuclear weapons and post - war policies regarding them inevitably led to the Interim Committee ' s involvement . Decision on use of atomic bombs . The most immediate of the committee ' s tasks , one that has been the focus of much subsequent controversy , was to make recommendations concerning the use of the atomic bomb against Japan . The committee ' s consensus , arrived at in a meeting held June 1 , 1945 , is described as follows in the meeting ' s log : One member , Bard , later dissented from this decision and in a memorandum to Stimson laid out a case for a warning to Japan before using the bomb . In arriving at its conclusion , the committee was advised by a Scientific Panel of four physicists from the Manhattan Project : Enrico Fermi and Arthur H . Compton of the Metallurgical Laboratory at the University of Chicago ; Ernest O . Lawrence of the Radiation Laboratory at the University of California at Berkeley ; and J . Robert Oppenheimer , who directed the bomb assembly program at Los Alamos . Reinforcing the decision arrived at on June 1 , the scientists wrote in a formal report on June 16 : Although the committee ' s recommendation was addressed to Stimson , Byrnes went directly from the June 1 meeting to brief Truman , who reportedly concurred with the committee ' s opinion . Reviewing the Scientific Panel ' s report on June 21 , the committee reaffirmed its position Press releases . The Interim Committee was given responsibility for the preparation of separate prepared statements for the President and the Secretary of War to be released when nuclear weapons were used . The job of drafting them was given to William Laurence . Laurence submitted them to Arthur W . Page for review , and he in turn passed them on to the Interim Committee . At its meeting on July 6 , the Interim Committee considered and adopted a set of British suggestions . The final draft of President Truman ' s speech was handed to him at the Potsdam Conference on August 1 . Following the dropping of an atomic bomb on the Japanese city of Hiroshima on August 6 , Truman read out the press release , which declared that : Post - war legislation . In July 1944 , before the Interim Committee was formed , Bush , Conant and Irvin Stewart had produced a proposal for legislation to control nuclear energy . Conant submitted the proposals to the Interim Committee at its meeting on July 9 , 1945 . Harrison brought in two experienced lawyers , Kenneth Royall and William L . Marbury to take up the job of drafting the legislation . Their draft bill would have created a nine - man commission consisting of five civilian and four military members . It granted the commission broad powers to acquire property , to operate facilities , to conduct research and to regulate all forms of nuclear energy . The Royall - Marbury bill was reviewed by the Interim Committee at its July 19 meeting and revised in line with their suggestions . The bill was forwarded to the President in August . The Interim Committee met again on September 28 to discuss legislative strategy . The Royall - Marbury bill was introduced into the United States Congress by the chairman of the House Military Affairs Committee , Andrew J . May , and the ranking member of the Senate Committee on Military Affairs , Senator Edwin C . Johnson on October 3 . It then became known as the May - Johnson bill . The May - Johnson bill soon ran into difficulties . Although the Interim Committee was discharged in November , it met one more time in December to discuss amendments to the May - Johnson bill . On December 20 , 1945 , Senator Brien McMahon introduced an alternative Senate bill on atomic energy , which quickly became known as the McMahon bill . This was initially a very liberal bill towards the control of scientific research , and was broadly supported by scientists . McMahon framed the controversy as a question of military versus civilian control of atomic energy , although the May - Johnson bill also provided for civilian control of atomic energy . In 1946 , several major revisions were made to the McMahon bill in order to appease the more conservative elements in the Senate . The resulting bill passed both the Senate and the House without major modifications . On August 1 , 1946 , Truman signed the McMahon bill into law as the Atomic Energy Act of 1946 .