 Wilkeson was sent to serve in the Army of the Potomac in Virginia, where he took part in the Overland Campaign of General Ulysses S. Grant.Wilkeson's unit was not actively engaged in the Battle of the Wilderness on May 5–6, 1864, so Wilkeson, overcome by youthful curiosity, took an unauthorized leave of absence from his battery and fought as an infantryman alongside elements of General Winfield Scott Hancock's Second Corps using a discarded musket he picked up on the battlefield.The following day he returned to his battery where he was punished for his absenteeism, then diligently remained with them during the subsequent Battle of Spotsylvania Courthouse, Battle of Cold Harbor, and opening stages of the Siege of Petersburg.