A native Virginian, Hill was a career United States Army officer who had fought in the Mexican–American War and Seminole Wars prior to joining the Confederacy. After the start of the American Civil War, he gained early fame as the commander of the "Light Division" in the Seven Days Battles and became one of Stonewall Jackson's ablest subordinates, distinguishing himself in the 1862 battles of Cedar Mountain, Second Bull Run, Antietam, and Fredericksburg.