Yount enlisted in the Union Army for a six-month term on November 9, 1861, and served in Company F of Phelps' Regiment of the Missouri Infantry. John W. Phelps, his commanding general, was an ardent abolitionist. Yount was wounded in the leg in a skirmish just before the Battle of Pea Ridge began on March 6, 1862, and taken prisoner by the Confederates. As a captive, he was marched more than to Fort Smith in his bare feet on cold, wet roads, and was held there as a POW for 28 days before his release in a prisoner exchange. He was discharged from the Union Army in May 1862.