King enlisted as Private in Company E, 1st Iowa Infantry on 20 April 1861. He mustered out on 21 August 1861. He then assisted in organizing the Kassuth Guards, which became Company K of the 14th Iowa Infantry with the rank of 2nd Lieutenant, the rank he held at Shiloh. At the Battle of Shiloh, King was listed as missing in action on 6 April 1862, becoming detached from his regiment during the chaotic fighting that day. He was later severely wounded in the right shoulder on 18 May 1864 at Yellow Bayou, Louisiana. After the war, he was elected in 1881 as Sergeant-At-Arms of the House of Representatives of the State of Nebraska.