Among his classmates were future general officers such as Robert Lee Bullard, Joseph E. Kuhn, Beaumont B. Buck, Charles Henry Muir, William Franklin Martin, George Washington Burr, Daniel Bradford Devore.

After America entered World War I in April 1917, Holbrook was promoted to brigadier general in command of the 165th Infantry Brigade.

[2] In 1902, Holbrook married Anna Huntington Stanley (1864 – 1907), daughter of Major General David S.

His military awards include the Army Distinguished Service Medal, the citation for which reads: The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pleasure in presenting the Army Distinguished Service Medal to Major General Willard Ames Holbrook, United States Army, for exceptionally meritorious and distinguished services to the Government of the United States, in a duty of great responsibility.

As Commanding General, Southern Department, where his firmness and tact in handling a threatening situation on the Mexican border materially improved conditions between the United States and Mexico.