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FINAL APPROVAL TO BUILD THE BOMB (Washington, D.C., December 1942)
Events
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Difficult Choices, 1942
Anxious as he was to get moving,
Leslie Groves decided to make one final
quality control check. On November 18, 1942, Groves
appointed Warren K. Lewis of the Massachusetts Institute
of Technology to head a final review committee, comprised
of himself and three DuPont representatives. During
the final two weeks of November, the committee traveled
from New York to Chicago to
Berkeley and back again through
Chicago. It endorsed the work on
gaseous diffusion at
Columbia, though it made some
organizational recommendations; in fact, the Lewis
committee advocated elevating gaseous diffusion to first
priority and expressed reservations about the
electromagnetic program despite an
impassioned presentation by
Ernest Lawrence in Berkeley. Upon
returning to Chicago, Crawford H. Greenewalt, a member of
the Lewis committee, was present at Stagg Field when
CP-1 (Chicago Pile #1) first went critical. (For more on CP-1, skip ahead to "Early Pile Design, 1942.") Significant as this moment was in the history
of physics, it came after the Lewis committee endorsed
moving piles to the pilot stage and one day after Groves
instructed DuPont to move into pile design and
construction.
The S-1 Executive Committee (left) met
to consider the Lewis report on December 9, 1942.
Most of the morning session was spent evaluating the
controversial recommendation that only a small
electromagnetic plant be built. Lewis and his
colleagues based their recommendation on the belief that
Lawrence could not produce enough uranium-235 to be of
military significance. But since Lawrence's
calutrons could provide enriched samples quickly, the
committee supported the construction of a small
electromagnetic plant.
James Conant disagreed with the Lewis
committee's assessment, believing that uranium had more
weapon potential than plutonium. And since he knew
that gaseous diffusion could not provide any enriched
uranium until the gaseous diffusion plant was in full
operation, he supported the one method that might, if all
went well, produce enough uranium to build a bomb in
1944. During the afternoon, the S-1 Executive
Committee went over a draft Groves had prepared for
Vannevar Bush to send to
President Franklin D. Roosevelt.
The draft supported the Lewis committee's report except
that it recommended skipping the pilot plant stage for the
pile. After Conant and the Lewis committee met on
December 10 and reached a compromise on an
intermediate-scale electromagnetic plant, Groves's draft
was amended and forwarded to Bush.
On December 28, 1942, President Roosevelt approved what
ultimately became a government investment in excess of $2
billion, $0.5 billion of which was itemized in Bush's
report submitted on December 16. The Manhattan
Project was authorized to build full-scale gaseous
diffusion and plutonium plants and the compromise
electromagnetic plant, as well as heavy water production
facilities. In his report, Bush reaffirmed his
belief that bombs possibly could be produced during the
first half of 1945 but cautioned that an earlier delivery
was unlikely. No schedule could guarantee that the
United States would overtake Germany in the race for the
bomb, but by the beginning of 1943 the Manhattan Project
had the complete support of President Roosevelt and the
military leadership, the services of some of the nation's
most distinguished scientists, and a sense of urgency
driven by fear. Much had been achieved in the year
between Pearl Harbor and the end of 1942.
No single decision created the American atomic bomb
project. Roosevelt's December 28 decision was almost
inevitable in light of numerous earlier ones that, in
incremental fashion, committed the United States to the
pursuit of atomic weapons. In fact, the essential
pieces were in place when
Roosevelt approved Bush's November 9, 1941 report on
January 19, 1942
(left). At that time, there was a science
organization at the highest level of the federal
government and a Top Policy Group with direct access to
the President. Funds were authorized, and the
participation of the Corps of Engineers had been approved
in principle. In addition, the country was at war
and its scientific leadership -- as well as its President
-- had the belief, born of
the MAUD Report, that the project could result in a significant
contribution to the war effort. Roosevelt's approval
of $500 million in late December 1942 was a step that
followed directly from the commitments made in January of
that year and stemmed logically from the President's
earliest tentative decisions in late 1939.
To view the next "event" of the Manhattan Project, proceed to
"1942-1944: The Uranium Path to the Bomb."
Previous
Sources and notes for this page.
The text for this page was adapted from, and portions
were taken directly from the
Office of History and Heritage Resources
publication:
F. G. Gosling,
The Manhattan Project: Making the Atomic Bomb
(DOE/MA-0001; Washington: History Division, Department
of Energy, January 1999), 16-17. For more on the Lewis Committee Report,
see the History Office publication: Richard G. Hewlett
and Oscar E. Anderson, Jr.,
The New World, 1939-1946: Volume I,
A History of the United States
Atomic Energy Commission
(Washington: U.S. Atomic Energy Commission, 1972),
113. The photograph of
Franklin Roosevelt is courtesy the
National Archives. Click
here for more information on the photograph of the
S-1 (Uranium) Committee. The photograph of
Vannevar Bush and
Arthur Compton is courtesy the
Lawrence Berkeley National Laboratory. The note from Roosevelt to Bush is available on
the National Archives microfilm collection M1392,
Bush-Conant File Relating to the Development of the
Atomic Bomb, 1940-1945
(Washington: National Archives and Records
Administration, 1990), reel #1/14.
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