When the Civil War began, French sided with the South. On February 12, 1861, French was appointed chief of ordnance of the state of Mississippi; and on October 23, 1861, he was appointed a brigadier general in the provisional army of the Confederate States of America. French became a major general on August 31, 1862. General French commanded a brigade and subsequently a division under Gen. Daniel Harvey Hill at Petersburg, Virginia. He led a demonstration against Harrison's Landing on July 4, 1862 and one against Suffolk, Virginia on September 22, 1862. (Fort French at Suffolk was named for him.) In 1863, French led a division under LTG James Longstreet in the Siege of Suffolk. French's division intervened in the Battle of Suffolk (Hill's Point), with its commander waiting for the federals who had seized Fort French to withdraw from their exposed position.