John W. Ogden left his job as a clerk in the summer of 1862 and enlisted in the Thirteenth New Jersey Infantry. He and his comrades had their baptism under fire at Antietam in September 1862. Eight months later the regiment was decimated at the Battle of Chancellorsville. According to one biographical sketch of the Thirteenth, “At Chancellorsville it behaved admirably throughout, again showing that it was made of royal stuff. The loss of the regiment in killed and wounded during the three days’ fighting was some 130, being nearly one-half the number taken into battle.”
Ogden was wounded slightly in the left cheek and was hospitalized. While he recuperated, the rest of the regiment participated in the Battle of Gettysburg. Ogden never returned to the Thirteenth. Considered unfit for combat duty, he joined the Veteran Reserve Corps, an organization created by the U.S. War Department for men unable to withstand the rigors of life in camp and on campaign, but able to serve light duty off the front lines.