Biddle was commissioned an engineer. Biddle was in charge of river and harbor work at
Nashville, Tennessee from 1891 to 1898. When the
Spanish–American War broke out, he became Chief Engineer of Volunteers, serving in
Puerto Rico,
Cuba, and the
Philippines. He was awarded the
Silver Star. From 1901 to 1907 he was Engineer-Commissioner in charge of public works in
Washington, D.C. Subsequently, he was in charge of river and harbor work in
San Francisco from 1907 to 1911 and then served as an observer with the
Austro-Hungarian Army on the
Eastern Front from November 1914 to June 1915. He then was in charge of river and harbor improvements in
Baltimore, Maryland. Biddle served as the superintendent of the US Military Academy at West Point from July 1916 to June 1917. When the United States entered World War I, he commanded a brigade of engineer regiments, then served as acting United States Army Chief of Staff in Washington while Chief of Staff
Tasker Bliss was in
London. In 1918 he was again sent overseas to take charge of American troops in Great Britain and Ireland. ==Death==