On September 30, 1862, Kiesewetter enlisted as a private in Company B, 46th Ohio Infantry during the American Civil War. At the Battle of Resaca, he was severely injured in the left hip May 14, 1864. He was confined to a bed for seven months, as the wound became gangrenous. With treatment from a surgeon, he recovered, and was discharged at Camp Chase, Columbus, March 31, 1865. He remained at the camp as a clerk until August 25, when he hired on as a bookkeeper at a Columbus firm. He remained there until 1878.