S-1 Executive Committee

In response, the Advisory Committee on Uranium was created at the National Bureau of Standards under the chairmanship of Lyman J. Briggs to determine the feasibility of nuclear weapons.

In June 1941, Roosevelt created the Office of Scientific Research and Development under the leadership of Vannevar Bush (OSRD), at it incorporated the NDRC, now under James B. Conant.

The S-1 Section coordinated research into nuclear weapons in United States, in cooperation with the British Tube Alloys project.

The United States Army created the Manhattan District in June 1942, and took over responsibility for the development of nuclear weapons from the S-1 Executive Committee in September 1942.

Even before publication, the news was brought to the United States by Danish physicist Niels Bohr, who opened the fifth Washington Conference on Theoretical Physics with Enrico Fermi on January 26, 1939.

The letter was signed by Albert Einstein on August 2, 1939, but its delivery was delayed because of the outbreak of World War II in Europe with the German invasion of Poland in September 1939.

"[3] As a result of the letter Roosevelt asked scientist Lyman J. Briggs, the director of the National Bureau of Standards, to organize an Advisory Committee on Uranium.

In addition to the committee members, it was attended by physicists Fred L. Mohler from the National Bureau of Standards and Richard B. Roberts from the Carnegie Institution of Washington, and Szilárd, Wigner and Edward Teller.

Adamson was skeptical about the prospect of building an atomic bomb, but was willing to authorize $6,000 (equivalent to $130,000 in 2023 current dollars) for the purchase of uranium and graphite for Szilárd and Fermi's experiments into producing a nuclear chain reaction at Columbia University.

[12] 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.

This time they were joined by Rear Admiral Harold G. Bowen, Sr., the director of the Naval Research Laboratory (NRL), along with Sachs, Pegram, Fermi, Szilard, and Wigner.

[17] The German invasion of Belgium in May 1940 generated concern over the fate of uranium ore from the Belgian Congo, the world's largest source;[17] the subsequent Battle of France created alarm in the administration over the direction the war was taking.

Briggs remained chairman, but Hoover and Adamson were dropped from its membership, while Tuve, Pegram, Beams, Gunn, and Urey were added.

[20] Meanwhile, Otto Frisch and Rudolf Peierls, two researchers at the University of Birmingham in England, who ironically had been assigned to investigate nuclear weapons by Mark Oliphant because, as enemy aliens in Britain, they were ineligible to participate in secret war work, issued the Frisch–Peierls memorandum in March 1940.

The memorandum contradicted the common thinking of the time that many tons of uranium would be needed to make a bomb, requiring delivery by ship.

The Committee unanimously recommended pursuing the development of an atomic bomb as a matter of urgency, although it recognised that the resources required might be beyond those available to Britain.

As a result of the MAUD Committee report, the British started an atomic bomb program under the codename Tube Alloys.

At Columbia, Urey had Karl P. Cohen investigate the process, and he produced a body of mathematical theory making it possible to design a centrifugal separation unit, which Westinghouse undertook to construct.

It issued a favorable report on May 17, 1941, recommending an intensified effort, but Bush was troubled by the emphasis on nuclear power instead of nuclear weapons, and had two engineers, Oliver E. Buckley from the Bell Telephone Laboratories and L. Warrington Chubb from Westinghouse added to produce a second report with an emphasis on estimating how soon practical benefits could be expected.

[30] On June 28, 1941, Roosevelt issued Executive Order 8807, creating the Office of Scientific Research and Development (OSRD),[31] with Bush as its director personally responsible to the president.

Harold D. Smith, the director of the Bureau of the Budget, gave Bush assurances that should OSRD resources prove insufficient, additional funding would be made available from monies controlled by the president.

[35] Oliphant flew to the United States from England in August 1941 to find out why Briggs and his committee were apparently ignoring the MAUD Report.

In these meetings Oliphant spoke of an atomic bomb with forcefulness and certainty, and explained that Britain did not have the resources to undertake the project alone, so it was up to the United States.

[41] The March 9, 1942, meeting of the S-1 Section was attended by Brigadier General Wilhelm D. Styer, the chief of staff of the newly created United States Army Services of Supply.

OSRD contracts were due to expire at the end of June, and with the country at war, there was intense competition for raw materials.

Colonel Leslie R. Groves, Jr., the head of the Construction Branch in the Office of the Chief of Engineers thought it would attract undue attention.

When he needed expert advice in May, he had called upon a smaller group, and he recommended that this supervise the OSRD work, mainly the technical and contractual aspects of the project, while the Army handled engineering, construction and site selection.

[46] The August 26, 1942, meeting considered Lawrence's electromagnetic separation project, and expansion of the program to produce heavy water.

He would be answerable to the Military Policy Committee (MPC), which would consist of Styer, Bush (with Conant as his alternate) and Rear Admiral William R.