The younger King entered the army as a private in Company F, 7th New York Militia, serving a three-month enlistment from April to June 1861.

He served in the Army of the Potomac throughout the war, eventually commanding (from 1864) 4th U.S. Light Artillery, Battery A, in the famed U.S.

[1] This used a counterweight to allow a 15-inch (381 mm) Rodman gun to be moved up and down a swiveling ramp, so the weapon could be reloaded, elevated, and traversed behind cover.

On March 22, 1898, the United States Army finally awarded King the Medal of Honor for his actions at White Oak Swamp.

Citation: This officer, when his captain was wounded, succeeded to the command of two batteries while engaged against a superior force of the enemy and fought his guns most gallantly until compelled to retire.