When the Civil War erupted, Wood enlisted at the age of 35 on April 4, 1861, in Brooklyn, New York, to serve three years. He was later wounded and captured on July 21, 1861, at the First Battle of Manassas. He was later exchanged for a Confederate colonel and returned to field duty. Later because of his wounds received at the battle of First Bull Run he was discharged for disability on October 18, 1861. After the war Alfred Wood became very involved in the post war affairs of his beloved 14th Brooklyn helping the veterans of the unit. He also became Mayor of the City of Brooklyn, 1864.