The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 8: Soldier Life and Secret Service.
Francis Trevelyan Miller, Ed.

as the conflict progressed the activities of the baser elements of society placed further burdens upon the Secret service. Smuggling, horse-stealing, and an illicit trade in liquor with the Army were only the lesser of the many crimes that inevitably arise from a state of war. Government employees and contractors conspired to perpetrate frauds. The practice of bounty-jumping assumed alarming proportions. Soldiers' discharges were forged and large sums collected upon them. Corrupt political organizations attempted to tamper with the soldiers' vote. The suppression of all this was added to the already heavy labors of the Secret agents.

there were, from the very beginning, several strongly concentrated centers of suspicion, and of these probably the most important and dangerous was located within the higher social circles of the city of Washington itself. In the spring of 1861, the capital was filled with people suspected of supplying information to the Confederate authorities. These Southern men and women did not forget the cause which their friends and families in the home-land were preparing valiantly to defend. Aristocratic people still opened their doors to those high in office, and who could tell what fatal secrets might be dropped by the guests, or inadvertently imparted, to be sent to the leaders of the South? nor were the activities confined entirely to homes. At office doors in the department buildings the Secret agents watched and waited to learn some scrap of information; military maps and plans were often missing after the exit of some visitor.

such vital information as this was constantly sent across the Potomac: ‘in a day or two, twelve hundred cavalry supported by four batteries of artillery will cross the River above to get behind Manassas and cut off railroad and other communications with our Army whilst an attack is made in front. For God's sake heed this. It is positive.’ and again: ‘today I have it in my power to say that Kelley is to advance on Winchester. Stone and Banks are to cross and go to ’