Drawing on oral testimony, previously unseen personal papers, and newly released archival information, this book provides a comprehensive account of British and American intelligence on the Soviet nuclear weapons program from 1945-1958. The book charts new territory, revising traditional accounts of Anglo-American nuclear relations and intelligence cooperation. It reveals how intelligence was collected: the roles played by defectors, aerial reconnaissance, and how novel forms of espionage were perfected to penetrate the Soviet nuclear program. It documents what conclusions were drawn from this information, and assesses the resulting estimates. Throughout the book a central theme is the Anglo-American partnership, depicting how it developed and how legal restrictions could be circumvented by cunning and guile.

"This is an important book on a little-known subject which, in its day, was of critical importance. Dr. Goodman describes, in meticulous detail, the extensive intelligence effort mounted to track Soviet development of nuclear weapons in the 1940s and 50s. This was a very hard target. Eric Welsh and his team, working closely with the Americans, were remarkably successful. Their success, achieved without agent penetration of the target, echoes that of R.V. Jones in World War II and demonstrates, as did Jones, that imagination and intense focus, plus (heretically) control of both collection and analysis, can yield high-quality results." - Former Chief of the British Secret Intelligence Service (MI6)