During the autumn of 1863 and through the winter, the regiment engaged in "desultory fighting". Gwyn served perfunctorily while in command of the 118th Regiment for the ensuing five months with no notable confrontations until the Battle of the Wilderness in May 1864. On the first day of battle, May 5, Gwyn was shot in the thigh, and put out of commission for at least one month. Gwyn would receive his promotion to colonel at Beverly Ford for his actions at Wilderness. Due to his injury, he was unable to lead the 118th Regiment into the multiple conflicts, including the Battle of Spotsylvania Court House, the Battle of North Anna, the Battle of Totopotomoy Creek, the Battle of Bethesda Church, and the Battle of Cold Harbor.