William B. Feis
When used in reference to the American Civil War, the phrase "intelligence activities" calls to mind tales of daring spies and their harrowing adventures. These prevalent images have fostered the mistaken impression that spies and espionage comprised the essence of Civil War intelligence operations. In reality, those engaged in intelligence work, or what contemporaries called secret service, included not only spies but also army scouts, cavalry patrols, government detectives, agents operating abroad, guides, couriers, telegraphers, aerial (balloon) observers, and Signal Corps personnel. To these people, intelligence simply meant information, not, as in the current definition, the end product of information analysis.
Both Federals and Confederates initiated ad hoc secret service operations on many levels and, in some cases, developed organizational structures to support them. However, neither side created a centralized, national-level agency to coordinate wartime diplomatic, political, and military intelligence efforts.
The literature on Civil War intelligence activities reflects the diverse nature of operations, sources, objectives, and personnel. The best overview remains Edwin C. Fishel "The Mythology of Civil War Intelligence" ( 1964) and the revised version, "Myths That Never Die" ( 1988). Fishel believes that the fascination with mythical cloak-and-dagger adventures has overshadowed the actual contributions of Civil War intelligence, and he challenges the most prevalent