During the Civil War, each side accused the other of mistreating prisoners of war. Today, most historians believe that there was systemic and deliberate abuse of POWs by both sides yet many base their conclusions on anecdotal evidence, much of it from postwar writings. Drawing on both contemporaneous prisoner diaries and Union Army documents (some newly discovered), the author presents a fresh and detailed study of supposed mistreatment of prisoners at Fort Delaware--one of the largest Union prison camps--and draws surprising conclusions, some of which have implications for the entire Union prison system.