Appointed from New York to the United States Military Academy (USMA), he graduated in the bottom half of his cadet class of 1896.

[1] Among his classmates at the academy there were several men who would, like Stewart himself, eventually attain the rank of general officer, such as Edward L. King, Lucious R. Holbrook, Dennis E. Nolan, Frank C. Bolles, LeRoy Eltinge and George H. Shelton.

Stewart was regimental commissary until his unit's deployment to the Philippine Islands in 1901, where he served first as quartermaster, then as garrison commander at Pagsanjan, Laguna.

He returned to Plattsburgh in 1916 to lead reserve officer training schools, and later that year received assignment as inspector general of the District of Columbia National Guard.

[3] After the war, Stewart returned to the permanent rank of major and commanded an Overseas Replacement Depot at Fort Meade, Maryland, served again at Fort Leavenworth and on the Army General Staff, and received promotions to permanent lieutenant colonel and colonel.

As Chief of Staff, 76th Division, from August 1917 until June 1918, he again showed tireless energy, practical resourcefulness, and military attainments of the highest order.