 Shortly after this appointment, and before its expiration, Buchanan commanded regulars and fought at the Battle of Antietam and at the Battle of Fredericksburg in 1862.Buchanan then went on recruiting duty and two months later was placed in command of the defenses of Fort Delaware, a prisoner of war facility, March–April, 1863.He then was assistant provost marshal general at Trenton, New Jersey, April 29, 1863–November 8, 1864.