 Having engaged the enemy that morning at Burnside's Bridge, they then led the 1st Brigade in its pursuit of CSA troops through Sharpsburg and its surrounding bluffs while under heavy enemy artillery and rifle fire.Continuing to march and skirmish periodically with the enemy that fall, they then fought again in the Battle of Fredericksburg (December 11–15).Still serving with the U.S. Army's 9th Corps during the opening months of 1863, Monaghan and the 48th Pennsylvania Infantry were transferred with their corps to duties in the west.