In 1862, after the outbreak of the Civil War, he enlisted in the Union Army as captain of Company H, 31st Iowa Volunteer Infantry Regiment. He was promoted to major in 1864, and served until the close of the war. He participated in the battles of Chickasaw Bayou, Arkansas Post, Siege of Vicksburg, Lookout Mountain, Missionary Ridge, Kennesaw Mountain, Atlanta, and Jonesboro, and Sherman's March to the Sea.