Francis Duncan was a historian for the Department of Energy's Atomic Energy Commission (AEC) from 1962 to 1987. During these years he coauthored, with Richard G. Hewlett, *Atomic Shield, the second volume of the AEC, and Nuclear Navy, 1946‒1962*. He holds M.A. and Ph.D. degrees in history from the University of Chicago. Dr. Duncan first met Adm. Hyman Rickover in 1969 while completing work on the AEC history. In 1974 he was assigned to the admiral's office to begin research for this study, and for the next eight years he watched Rickover and his "Naval Reactors" at work and engaged in frank discussions with a variety of people associated with the nuclear propulsion program. Dr. Duncan is retired and lives in Bethesda, Maryland.