Godman enlisted April 26, 1861 as a Major in the Union Army during the American Civil War in the 4th Ohio Infantry, promoted to lieutenant colonel January 9, 1862, and to colonel November 29, 1862. He was severely wounded at Fredericksburg and honorably discharged July 28, 1863. March 13, 1865 he received the rank brevet brigadier general. He was elected as a Republican for State Auditor in 1863, and re-elected in 1867, serving eight years.