The state of military intelligence at the beginning of the Civil War was haphazard at best and nonexistent at its worst. The realities of war forced the Union Army of the Potomac to move from the civilian guesses of Allen Pinkerton to a highly sophisticated system of analysis and information collection led by dedicated officers and a cadre of intrepid scouts (Civil War slang for spies). This development in no small way led to the eventual defeat of the Confederate Army of Northern Virginia and laid the groundwork for the establishment of military intelligence as an accepted and vital part of the American Army structure.