He resigned his school post to enlist in the Union Army following the outbreak of the American Civil War and raised a company for the Twentieth Regiment, Michigan Infantry who mustered him into service as a Second Lieutenant. On July 29, 1862, he was made captain of his company and on October 14, 1862, he was made major of the Twentieth Regiment. On November 16, 1863, he was promoted to lieutenant colonel, and by order of the U.S. War Department, he was made colonel on November 21, 1863.