he U.S. Army played a key role in the formation and administration of the Manhattan Project, the World War II organization which produced the atomic bombs that not only contributed decisively to ending the war with Japan but also opened the way to a new atomic age. The volume begins with a prologue, designed to provide the reader with a brief survey of the history of atomic energy and to explain in layman’s terms certain technical aspects of atomic science essential to an understanding of the major problems occurring in the development of an atomic weapon. Early chapters describe the beginning of the Army’s atomic mission, including the formation of the Manhattan District, the first steps in acquiring the means to produce atomic weapons and the appointment of General Groves. Subsequent topical chapters trace the building and operation of the large-scale process plants for the production of fissionable materials; the administration of a broad range of support activities, such as security and community management; and the fabrication, testing, and combat employment of atomic bombs. A concluding section describes how the Army dealt with the difficult problems arising during its unexpectedly prolonged postwar trusteeship of the project until December 1946, when the newly created civilian agency – the United States Atomic Energy Commission – assumed responsibility for atomic energy matters.