When word came of Tennessee's secession, Jackson resigned from the Army on May 16, 1861, and returned to the South to enroll in the Confederate army. He was commissioned as a captain of artillery. He served as an aide-de-camp to General Gideon Pillow and at the Battle of Belmont in November. In early 1862, Jackson was appointed as colonel of the 1st Tennessee Cavalry and rose to be chief of cavalry, serving under John C. Pemberton, Earl Van Dorn, and lastly Sterling Price. On December 29, 1862, he was promoted to brigadier general.
