When the U.S. Civil War erupted, Horatio C. King sought a commission in the US Army and in 1862 he was appointed as Assistant Quartermaster of volunteers with the rank of Captain in the Army of the Potomac. He was soon promoted to Chief Quartermaster of the First Cavalry Division of the Army of the Shenandoah and served in five battles. While serving under General Sheridan during the Battle of Five Forks, near Dinwiddie Courthouse, Virginia, King earned the Congressional Medal of Honor for gallantry and was promoted to Major. He was honorably discharged in October 1866 with the brevets of Major, Lieutenant Colonel, and Colonel. Following his war time service, King continued to serve the military in various positions. He joined the New York National Guard in 1876 and served as Major of the Thirteenth Regiment and was then appointed to be judge advocate of the Eleventh Brigade in 1880. In 1883, he was appointed to be judge advocate general, with the rank of Brigadier General. Later, King served as secretary of the Society of the Army of the Potomac from 1877 to 1904 and as president in 1904. He was a charter member of the New York Commandery of the Military Order of the Loyal Legion and the Grand Army of the Republic, serving two years as post commander and on year as department judge advocate general. During the period 1862 – 1866, Colonel King participated in and sustained combat operations as the Assistant Quartermaster and Chief Quartermaster of the First Cavalry Division of the Army of the Shenandoah, serving in five battles. While serving under General Sheridan during the Battle of Five Forks, near Dinwiddie Courthouse, Virginia, King earned the Congressional Medal of Honor on March 31, 1865 for gallantry and was promoted to Major. CITATION: “While serving as a volunteer aide, carried orders to the reserve brigade and participated with it in the charge which repulsed the enemy.” Following his active service, King relied on his combat experience to advance Army doctrine and procedures in the New York National Guard. He joined the New York National Guard in 1876 and served as Major of the Thirteenth Regiment and was then appointed to be judge advocate of the Eleventh Brigade in 1880 and, in 1883, was appointed to be judge advocate general, with the rank of Brigadier General.