At the beginning of the American Civil War, he enlisted in the Union Army, and was made captain of a company of the Third Missouri Infantry on April 22, 1861. He was captured at Neosho, Missouri on July 5, 1861 and was exchanged. In September 1861, he was promoted to major of the Fifteenth Missouri Infantry. He fought in the battles of Wilson's Creek, Carthage, Pea Ridge, Corinth, Perryville, Chickamauga, and Missionary Ridge.