Major Coker answered the call to defend the right to own enslaved people when the Civil War began, and fought for the 6th and 9th South Carolina Regiments at First Manassas, the Battle of Malvern Hill, Second Manassas, the Battle of Harpers Ferry, and Antietam. In October 1863, Major Coker was wounded at the Battle of Chickamauga, and after a time as a prisoner of war, returned home to spend the rest of his life nursing a shattered hip.