I think Bruce Catton is a good scholar of the era. His essay on the 100th anniversary of the emancipation proclamation is telling
Union armies which invaded the South confiscated or destroyed property that helped their foes baled cotton, railroad tracks, factories, stores of food, and the like. Precisely because the slave was admitted to be property, it seemed logical to remove him from his secessionist owners; quite early in the war Maj. Gen. Ben Butler announced that slaves who fled from Confederate masters were Âcontraband of war and could be confiscated like other contraband, and the War Department accepted his view.
http://www.nps.gov/a...ulture/catton.htm