* All sources cited in the text are listed alphabetically in the
reference list at the end of this volume. The number given in the
text corresponds to the number of the source document in the reference
list.

In response to the potential threat of a German nuclear weapon, the
United States sought a source of uranium to use in determining the
feasibility of a nuclear chain reaction. After Germany occupied
Belgium in May 1940, the Belgians turned over uranium ore from their
holdings in the Belgian Congo to the United States. Then, in March
1941, the element plutonium was isolated, and the plutonium-239
isotope was found to fission as readily as the scarce uranium isotope,
uranium-235. The plutonium, produced in a uranium-fueled nuclear
reactor, provided the United States with an additional source of
material for nuclear weapons (7; 12).

In the summer of 1941, the British Government published a report
written by the Committee for Military Application of Uranium
Detonation (MAUD). This report stated that a nuclear weapon was
possible and concluded that its construction should begin immediately.
The MAUD report, and to a lesser degree the discovery of plutonium,
encouraged American leaders to think more seriously about developing a
nuclear weapon. On 6 December 1941, President Roosevelt appointed the
S-1 Committee to determine if the United States could construct a
nuclear weapon. Six months later, the S-1 Committee gave the
President its report, recommending a fast-paced program that would
cost up to $100 million and that might produce the weapon by July 1944
(12).

The President accepted the S-1 Committee's recommendations. The
effort to construct the weapon was turned over to the War Department,
which assigned the task to the Army Corps of Engineers. In September
1942, the Corps of Engineers established the Manhattan Engineer
District to oversee the development of a nuclear weapon. This effort
was code-named the "Manhattan Project" (12).

Within the next two years, the MED built laboratories and production
plants throughout the United States. The three principal centers of
the Manhattan Project were the Hanford, Washington, Plutonium
Production Plant; the Oak Ridge, Tennessee, U-235 Production Plant;
and the Los Alamos Scientific Laboratory in northern New Mexico. At
LASL, Manhattan Project scientists and technicians, directed by Dr. J.
Robert Oppenheimer,* investigated the theoretical problems that