[3] Hornbrook was then selected to attend the United States Military Academy (USMA) at West Point, New York, from where he graduated in 1890.

[1] Hornbrook returned stateside on July 31, 1918, and was stationed at Headquarters for the Southern Department until August 11, 1918.

[1] He was honorably discharged from federal service as a brigadier general on March 10, 1919.

[2] From October 1, 1919, to May 26, 1920, Hornbrook commanded the 5th Cavalry Regiment at Big Bend District, Texas.

[2] In 1895, Hornbrook married Mary Worth Sanno, the daughter of Brigadier General James M. J. Sanno (1840–1907), a career army officer and Union veteran of the American Civil War.