In August 1862, during the American Civil War, he enlisted and was mustered in as a sergeant in Company G., 128th New York Infantry Regiment. He was promoted to first sergeant in July 1863. In September 1863, he was discharged to accept a commission as first lieutenant of Corps de Afrique, 91st United States Infantry, a regiment of black soldiers he and others from the 128th Regiment helped organize. He served in the 91st for the rest of the war. He fought in Port Hudson and the Red River Campaign. He was the eldest of four brothers that fought in the Civil War, two of whom were killed in the war. After the war, he returned to Columbia County, where he studied law and was admitted to the bar in 1867.