Bureau of Military Information

[citation needed] In all cases, the detectives and spies in question were civilians, despite the fact they reported to military heads and served in wartime (Pinkerton, however, created an alias that was a Union Army major).

They also reported directly to and were paid at the leisure of their superiors, not to any military or government agency, and in fact, Pinkerton and Baker's organizations actively competed against one another, to the point of arresting each other's agents to maintain an upper hand.

In addition to field agents, information was gathered through interrogation of prisoners of war and refugees, newspapers, and documents left on the battlefield by Confederate officers who had retreated or been killed.

Sharpe and BMI continued to serve Grant up until the Battle of Appomattox Court House, where they were responsible for paroling the former members of the Army of Northern Virginia, including Robert E. Lee himself.

Following Lincoln's assassination, Baker would be responsible for tracking down the conspirators, but would eventually be dismissed by Andrew Johnson due to allegedly spying on the President himself for Edwin M. Stanton.