Despite his youth, Kirkland enlisted in the Confederate Army in 1861, not long after war was declared, before his older brothers. He was first assigned to Company E, 2nd South Carolina Volunteer Infantry, but was later transferred to Company G of the same regiment, and was promoted to sergeant. He first saw action during the First Battle of Bull Run (First Manassas), and later in the Battle of Savage's Station, Battle for Maryland Heights and Battle of Antietam, during which time many of his closest friends from Kershaw County were killed.