Jacob served as a Corporal with the 28th Regiment, PA Volunteer Infantry, Company H. He mustered into service on July 9, 1861. He was wounded at Antietam on September 17, 1862. He was discharged on Surgeon's certificated on February 16, 1863. Jacob later served with the 2nd Heavy Artillery/112th Regiment, Battery H. He served with this regiment from 9 Feb 1864 to 29 Jan 1866. He was promoted to Full Corporal on 1 Jul 1865. He mustered out at City Point, VA.
Wounded at Battle of Antietam
Jacob's regiment moved out of the "East Woods" to repeal the Confederate forces at the edge of the "Cornfield." The attack was successful but Jacob was shot in the left heel and had to be hospitalized. He was later discharged from duty.