"The Union defeat at the First Battle of Bull Run on July 21, 1861 jolted Congress into a realization that the Civil War might not be the swift, neat confrontation they hoped for – and that disunionists might need to be held legally liable for their actions. "The Northern armies ran against slavery immediately." Lincoln biographer Robert Morse wrote that "thousands of slaves at Manassas were doing the work of laborers and servants, and rendering all the whites of the Southern army available for fighting. The handicap was so severe and obvious, that it immediately provoked the introduction of a bill freeing slaves belonging to rebels and used for carrying on the war."