Though neither the North nor the South had a formal military intelligence network during the Civil War, each side obtained crucial information from spying or espionage operations. From early in the war, the Confederacy set up a spy network in the federal capital of Washington, D.C., home to many southern sympathizers. The Confederate Signal Corps also included a covert intelligence agency known as the Secret Service Bureau, which managed spying operations along the so-called “Secret Line” from Washington to Richmond. As the Union had no centralized military intelligence agency, individual generals took charge of intelligence gathering for their own operations. General George B. McClellan hired the prominent Chicago detective Allan Pinkerton
