A Southern sympathizer, Hatfield enlisted in the Confederate Army during the American Civil War. He was commissioned a First Lieutenant of Cavalry in the Virginia State Line in 1862, a group made to protect the territory along the Kentucky-Virginia border where resident loyalties to the North and South were mixed. The Virginia State Line eventually disbanded in 1863 and Hatfield enlisted as a private in the newly formed 45th Battalion Virginia Infantry, before being appointed first lieutenant and later captain of Company B. His unit spent most of its time patrolling the border area against bushwhackers sympathetic to the Union as well as engaging in guerrilla warfare against Union soldiers. Devil Anse himself has been connected to battles and killings of several Union fighters, including trackers Ax and Fleming Hurley in 1863.