Dixon was a member of a pre-war militia company, the Washington Light Infantry of Mobile. In the autumn of 1861, the Washington Light Infantry became Company A, 21st Alabama Infantry Regiment. Dixon by then was a sergeant. He would later be promoted to lieutenant. In March 1862, Dixon's regiment proceeded to Corinth, Mississippi, and the following month took an active part in the Battle of Shiloh, losing 200 men killed or wounded out of the 650 engaged. Dixon himself was severely wounded in the left leg. Luckily, a $20 gold coin he carried as a good luck piece saved his leg, and possibly his life. However, the impact seriously damaged his femur and Dixon would limp for the rest of his short life. Following the battle, the regiment was reorganized and returned to Mobile to man the city's defenses as artillerymen. It was during the uneventful garrison duty at Mobile that Dixon became interested in the submarine that Horace Lawson Hunley was building.