This well-researched book examines the first several years of the U.S. and Soviet atomic bomb programs, to show what each side was actually doing and, more importantly, what each side thought the other was doing. Stressing the importance of intelligence in forming those perceptions and in fueling the arms race, the book focuses mainly on the period from the detonation of the first atomic bomb (July 16, 1945, New Mexico) to the first successful test of a nuclear weapon by the Soviet Union (August 29, 1949, Kazakhstan). The author emphasizes the role of international contributions, especially materials and technology, in the development of nuclear weapons programs of each nuclear state. Extensive endnotes accompany each chapter.