Enlisting as a cornet player, he rose in rank to become the principal musician of the 1st Vermont Volunteer Infantry Regiment during the Spanish–American War.

[5][6] Following the Spanish–American War Tillotson resigned from the Central Vermont Railroad to pursue legal studies in the office of St. Albans Attorney Alfred A.

[11] Tillotson's appointment was a generational break, because he was the first Vermont Adjutant General since the American Civil War who was not a veteran of that conflict.

Tillotson won reelection every two years, and continued to serve as Adjutant General until the start of World War I.

In April 1920 he transferred to the Infantry branch, and his postings included adjutant and executive officer of the 21st Regiment, Hawaiian Division.

[24][25][26] During his Army service Tillotson authored The Articles of War, Annotated and Index/Digest to Uniform Code of Military Justice.

Initially he resided in Springfield and practiced law with Alban J. Parker, who went on to serve as Vermont Attorney General.

Tillotson remained active, including serving on Newfane's Board of Selectmen and authoring numerous articles on American history and other topics.

[31] Tillotson died at the hospital in Townshend, Vermont on July 18, 1957, as the result of complications from a fall that left him with a fractured hip.