 After the Battle of Fredericksburg, he was promoted to colonel, and assigned to command the 12th South Carolina Infantry after the previous commander resigned.This unit was part of Colonel Abner Monroe Perrin's First Brigade
of a division commanded by General William Dorsey Pender.Miller first led this unit at the Battle of Chancellorsville, and in the aftermath of this significant Confederate victory, was assigned to March 2000 Union prisoners to Richmond, Virginia.