Battle of Fredericksburg
Johnson was a member of the 2nd Wisconsin Volunteer Infantry Regiment, part of the Iron Brigade. He earned his medal of honor for valor displayed at the Battle of Antietam and the Battle of Fredericksburg. During the Battle of Fredericksburg, while loading a cannon, Confederate artillery fire severed his right arm. He continued to load with his left arm until blood loss caused him to faint. He was discharged from the Army on April 10, 1863.