"This document highlights how the north and south gathered and used their information, the important missions, and the personalities. Though much has been written about the Civil War itself, little has been written about the spy war that went on within. The chronicling of Civil War intelligence activities challenges historians because of the lack of records, the lack of access to records, and the questionable truth of other records. Judah P. Benjamin, the Confederacy's Secretary of State, burned all the intelligence records he could find as federal troops entered Richmond. Union intelligence records were kept sealed in the National Archives until 1953. A few individuals involved in intelligence gathering burned their personal papers while others chose to publish their memoirs, though greatly embellishing their exploits. Even today, the identities of many spies remain secret. Henry Thomas Harrison, for example, was a Confederate spy whose intelligence set in motion the events that produced the battle of Gettysburg. But neither his first name nor details of his long career as a spy were known until 1986, when historian James O. Hall published an article about him."