Hume served in the National Guard, and was commissioned in the 2nd Maine Infantry on April 2, 1894. After he finished school, Hume returned to Bridgewater and formed his own army. He was able to secure recognition from the state of Maine. The outfit was designated Company L,
National Guard of the State of Maine. He continued to gradually earn promotions throughout his service with the Maine militia. Hume enlisted in the 2nd Maine Infantry for the
Spanish–American War. He also earned the Distinguished Service Medal for "exceptionally meritorious and distinguished services while in command of the 103rd Infantry, during the St. Mihiel and Meuse-Argonne operations." Three days before the
armistice, Colonel Hume and Colonel
Edward L. Logan were removed from their positions. He was later reinstated on February 4, 1919. It was speculated that the
Regular Army officers were trying to get rid of any National Guard officers so that the "regulars may get the glory and lead the boys back home". ==Post-war==