At the break of the Civil War and with high confidence, Walker tried to enlist in the Union Army. She was denied because of her gender but did not take no for an answer. Trying again, she enlisted as a surgeon in the war and was transferred to the 52nd Ohio Infantry. Later she was appointed assistant surgeon. This was a very big accomplishment for a woman at this time.  During one of her trips to the Confederacy to tend to the sick and wounded, she was captured. During 1864 Walker was imprisoned for four months in Richmond, Virginia. After four months Walker, along with other surgeons in the Union, were released in a trade for 17 Confederate doctors. Even after her capture, Walker still continued to cross the line between the Confederates and Union to tend to the sick and wounded even after her experience of being imprisoned with the Confederates. Until the war ended, Walker remained with the 52nd Ohio Infantry, tending to the sick and wounded. Mary Edward Walker’s persistence and determination paid off as she served the sick and wounded on the battlefield, refusing to be pulled down because of her gender. 