[3] Among his classmates were several future general officers, including Charles Gerhardt, Charles S. Farnsworth, Nathaniel Fish McClure, Michael Joseph Lenihan, Herman Hall, William Weigel, Ernest Hinds, Mark L. Hersey, James Theodore Dean, Frank Herman Albright, Marcus Daniel Cronin, George Owen Squier, Thomas Grafton Hanson, George Washington Gatchell, Alexander Lucian Dade and Ulysses G.

[6] During the Spanish–American War, he was first posted to Fort Huachuca, Arizona, where his regiment conducted security patrols on the Mexico–United States border.

[6] Again assigned as regimental adjutant, Wittenmyer was with the 15th Infantry in the autumn of 1899, when it participated in the China Relief Expedition.

[6] In October 1906, his regiment deployed as part of the Army of Cuban Pacification during the Second Occupation of Cuba, and he served there until 1908.

[6] Upon returning to the United States, Wittenmyer was assigned as the 5th Infantry's adjutant, a post he held until January 1910.

[8] After serving on the War College staff, Wittenmyer was assigned to the 27th Infantry at Fort Sheridan, Illinois.

[8] In August 1917, Wittenmyer was promoted to temporary brigadier general for World War I and assigned to command of the 153rd Infantry Brigade, a unit of the 77th Division.

[8] After the armistice ended the war, Wittenmyer remained in command of the 7th Division as it occupied positions near Toul, France.

[10] In addition, he was awarded France's Legion of Honor (Commander) and Croix de Guerre with Palm.

[12] After the war, Wittenmyer was reduced to his permanent rank of colonel and assigned as chief of staff for the Ninth Corps Area.

In retirement, he lived with a sister in law and her family near Peebles, Ohio and operated a farm in nearby Lawshe, Meigs Township.

[10] In 1936, Wittenmyer became ill after an automobile accident, and sought treatment at the military hospital in Hot Springs, Arkansas.