FINAL APPROVAL TO BUILD THE BOMB
(Washington, D.C., December 1942)
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
Technology to head a final review committee, comprised of himself and
DuPont representatives. During the final two weeks of November,
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
elevating gaseous diffusion to first priority and expressed
the electromagnetic program
impassioned presentation by Ernest
Berkeley. Upon returning to Chicago, Crawford H. Greenewalt, a
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
recommendation that only a small electromagnetic plant be built.
his colleagues based their recommendation on the belief that Lawrence
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
potential than plutonium. And since he knew that gaseous
not provide any enriched uranium until the gaseous diffusion plant was
operation, he supported the one method that might, if all went well,
enough uranium to build a bomb in 1944. During the afternoon, the
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
the pilot plant stage for the pile. After Conant and the Lewis
met on December 10 and reached a compromise on an intermediate-scale
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
of which was itemized in Bush's report submitted on December 16.
Manhattan Project was authorized to build full-scale gaseous diffusion
plutonium plants and the compromise electromagnetic plant, as well as
water production facilities. In his report, Bush reaffirmed
that bombs possibly could be produced during the first half of 1945 but
cautioned that an earlier delivery was unlikely. No schedule
guarantee that the United States would overtake Germany in the race for
bomb, but by the beginning of 1943 the Manhattan Project had the
support of President Roosevelt and the military leadership, the
services of some
of the nation's most distinguished scientists, and a sense of urgency
fear. Much had been achieved in the year between Pearl Harbor and
single decision created the American atomic bomb project.
Roosevelt's December 28 decision was almost inevitable in light of
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
that time, there was a science organization at the highest level of the
government and a Top Policy Group with direct access to the
Funds were authorized, and the participation of the Corps of Engineers
approved in principle. In addition, the country was at war and
scientific leadership -- as well as its President -- had the belief,
born of the
MAUD Report, that the project could result in a significant
to the war effort. Roosevelt's approval of $500 million in late
1942 was a step that followed directly from the commitments made in
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."
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.
Home | History
Office | OpenNet | DOE | Privacy and Security Notices
About this Site | How to Navigate this Site | Note on Sources |
Site Map | Contact Us