S - 1 Uranium Committee The S - 1 Uranium Committee was a Committee of the National Defense Research Committee that succeeded the Briggs Advisory Committee on Uranium and later evolved into the Manhattan Project . World War II begins . World War II began with the German invasion of Poland on September 1 , 1939 , prompting Albert Einstein and Leó Szilárd to complete the letter to U . S . President Franklin Delano Roosevelt they had been working on over the summer . This letter was signed by Einstein on August 2 , and it was hand - delivered to Roosevelt by the economist Alexander Sachs on October 11 , 1939 . The letter advised Roosevelt of the existence of the German nuclear energy project and warned that it was likely the Germans were working on an atomic bomb using uranium , and that the U . S . should be concerned about locating sources of uranium and researching nuclear weapon technology . At this time the U . S . policy was neutral in the war . Experiments with the fission of uranium were already going on at universities and research institutes in the United States . Alfred Lee Loomis was supporting Ernest Lawrence at Berkeley Radiation Laboratory and Enrico Fermi at Columbia . Vannevar Bush was also doing similar research at Washington , D . C . - based Carnegie Institution . After the April 29 , 1940 spring meeting of the American Physical Society , the " New York Times " reported that conferees argued " the probability of some scientist blowing up a sizable portion of the earth with a tiny bit of uranium . " Briggs Advisory Committee on Uranium . As a result of the letter Roosevelt asked Lyman James Briggs , director of the National Bureau of Standards , secretly to organize the Briggs Advisory Committee on Uranium . The committee ' s first meeting was on October 21 , 1939 , in Washington , D . C . ; $ 6 , 000 was budgeted for conducting neutron experiments conducted by Fermi and Szilárd at Columbia . Four aspects of uranium seem to be critical from the start : The MAUD committee . In England , Otto Frisch and Rudolf Peierls , two researchers at Birmingham University , issued the Frisch – Peierls memorandum in March 1940 . The memorandum contradicted the common thinking of the time that many tons of uranium - 235 would be needed to make a bomb , requiring delivery by ship . The calculation in the memorandum showed that a bomb might be possible using as little as one pound of uranium - 235 , and could be quite practical for aircraft to carry . Frisch and Peierls ' s professor , Marcus Oliphant , passed the memorandum on to Henry Tizard , chairman of the Committee on the Scientific Survey of Air Defence who requested the MAUD Committee be established secretly - the " MAUD " standing for " Military Application of Uranium Detonation " . The first meeting was on April 10 , 1940 and the committee consisted of Sir George Paget Thomson as chairman and Marcus Oliphant , Patrick Blackett , James Chadwick , Philip Moon , and John Cockcroft as members . Ralph H . Fowler was also asked to send the progress reports to Lyman Briggs . The MAUD Committee completed the MAUD report on July 15 , 1941 , and disbanded . The report had two parts : the first concluding that a uranium - 235 bomb would be feasible using 26 pounds of active metal with a yield equivalent to 1800 tons of trinitrotoluene ( TNT ) . The second concludes that the controlled fission of uranium - 235 could be a source of heat energy for powering machines and a source of radio - isotopes . On April 14 , 1941 , Lyman Briggs received a note from Eugene Wigner , stating : In the meantime , the NDRC under the leadership of Vannevar Bush was also exploring the possibility of using nuclear power for peaceful energy . A favorable report by Arthur Compton and the National Academy of Sciences was issued May 17 , 1941 , and after consultation with Roosevelt , Bush created the Office of Scientific Research and Development . On July 1 , 1941 , Bush assumed responsibility for all fission research and the Advisory Committee became the S - 1 project of the NDRC . with Lyman Briggs reporting to Bush . Marcus Oliphant came to the United States from England in August 1941 to find out why Briggs and his committee were apparently ignoring the MAUD Report . Oliphant discovered to his dismay that the reports and other documents sent directly to Briggs had not been shared with the Advisory Committee . Oliphant then met with the Uranium Committee and his colleagues Ernest Lawrence , James Conant and Enrico Fermi to explain the urgency . In these meetings Oliphant spoke of a " bomb " with certainty and explained that Britain did not have the resources to undertake the project so it was up to the United States . S - 1 project . On December 6 , 1941 , Vannevar Bush held a meeting to organize an accelerated uranium - 235 research project managed by Arthur Compton , with Harold Urey researching gaseous diffusion for uranium enrichment and Ernest Lawrence to research electromagnetic enrichment techniques . The next day , the Japanese Empire ' s attack on Pearl Harbor led to the United States entry into the war . Four days later , Germany declared war on the United States . At a meeting on December 18 the S - 1 project was dedicated to development of a uranium bomb . As a result of the MAUD Report , the British had started a uranium bomb program referred to by the codename Tube Alloys . Perceived slowness on the part of the United States had become a contentious issue between American and British scientists . Upon entry into the war , the U . S . placed increasing importance on working cooperatively with the British program . Roosevelt wrote a note to Winston Churchill outlining increased U . S . – UK cooperation , but was rebuffed by Churchill . Apparently the British felt the U . S . could add little to the effort at that point . This rebuff turned out to be a major blunder as the U . S . effort quickly caught up with the British effort , and the British realised that their pioneering effort would have no value if it were not quickly capitalized . Leadership of the American atomic ( uranium ) bomb project was transferred to U . S . Army General Leslie Groves from September 1942 ; Groves ( in his own words ) had never trusted the British , or anyone else . On June 17 , 1942 , Roosevelt approved a proposal by Bush to dissolve the original S - 1 Section and created the S - 1 Executive Committee , chaired by James B . Conant , with the membership of Briggs , Compton , Urey , Lawrence , and Eger Murphree . The program entered into increased cooperation between the OSRD and the U . S . Army . On August 13 , 1942 , the Manhattan Project was created by the U . S . Army Corps of Engineers , and on September 23 , 1942 , command of the district was given to Groves . The S - 1 Executive Committee created two more secret sites : " Site X " in Tennessee ( Oak Ridge , Tennessee ) , where uranium - 235 isotope separation was carried out at the Y - 12 , K - 25 , and S - 50 sites , and " Site Y , " a secret laboratory at Los Alamos in northern New Mexico ( later Los Alamos National Laboratory ) , where the bomb design was developed . As the Army role in the project grew larger , the role of the OSRD became more advisory . Eventually , in May 1943 , the Army took full control over the OSRD ' s research and development contracts , and as such the S - 1 Executive Committee became essentially inactive though never formally dissolved . Bush , Conant , and other OSRD insiders continued their influence in the Manhattan Project through their participation in the Military Policy Committee .