Clitz, whose deteriorating mental state had been noticed by relatives for several months, disappeared at Niagara Falls, New York, and was presumed drowned on October 30, 1888.

[4] Clitz received a brevet appointment as first lieutenant in the Regular Army on April 18, 1847, for gallant and meritorious conduct at the Battle of Cerro Gordo.

[4] Clitz was an original member of the Aztec Club of 1847, which was founded as a military society of officers who served with the United States Army in the Mexican–American War.

[1][4] Upon leaving West Point, Clitz was assigned to frontier duty at Santa Fe, New Mexico, in 1856.

[12] Clitz served in the defense of Fort Pickens, Florida from Confederate States Army assault between April 19, 1861, and June 27, 1861.

[12][13] At the Battle of Gaines's Mill on June 27, 1862, Clitz was severely wounded in both legs and captured by the Confederate forces.

[14] The 12th and 14th US Infantry Regiments were attacked by a much larger Confederate force as they tried to hold the line while Union Army wagons and other units withdrew.

[14] Clitz was taken to the McGehee House, a prominent battlefield landmark, where his Mexican–American War colleague, Confederate Major General D. H. Hill called for a surgeon to dress his old friend's wounds.

[15] Clitz was appointed brevet lieutenant colonel in the Regular Army to rank from June 27, 1862, for gallant and meritorious conduct at the Battle of Gaines's Mill, Virginia.

[1][8][12][16] Clitz served at the US Military Academy, as Commandant of Cadets and Instructor of Artillery, Infantry, and Cavalry Tactics, from October 23, 1862, to July 4, 1864.

[1][10][12] Following his service at West Point, Clitz served on garrison duty at Bedloe's Island, New York City, from July 1864 to May 1865.

[12] For his "gallant and meritorious services during the Rebellion" he received a brevet appointment as colonel in the Regular Army.

Commanding General William T. Sherman supported these recommendations but they failed to gain adherence from many older officers and the US Army bureaucracy.