Grenville Mellen Dodge was a Union Army officer on the frontier and a pioneering figure in military intelligence during the Civil War, who served as Ulysses S. Grant's intelligence chief in the Western Theater. He served in several notable assignments, including command of the XVI Corps during the Atlanta Campaign.

Tactical or battlefield intelligence became vital to both sides in the field during the American Civil War. Units of spies and scouts reported directly to the commanders of armies in the field, providing details on troop movements and strengths. The distinction between spies and scouts was one that had life or death consequences: if a suspect was seized while in disguise and not in his army's uniform, he was often sentenced to be hanged. A spy named Will Talbot, a member of the 35th Battalion, Virginia Cavalry, was left behind in Gettysburg after his battalion had passed through the borough on June 26–27, 1863. He was captured, taken to Emmitsburg, Maryland, and executed on orders of Brig. Gen. John Buford.