Colonel David Noel Tool was commissioned as an Infantry Officer upon graduation from Infantry Officer Candidate School, class 6-65 at Fort Benning, Georgia on 22 June, 1965. His first duty assignment was as a Personnel Officer, United States Army Training Center, Fort Jackson, South Carolina.

His subsequent duty assignments were: Rifle/Weapons Platform Leader/ Executive Officer, Company B, 2nd Battalion, 16th Infantry Brigade, 1st Infantry Division, Vietnam; Transpiration Officer, Army Terminal Unit, Charleston, South Carolina; Arts & Monuments Officer, 301st Civil Affairs Battalion, Los Angeles, California; Psychological Operations Officer, 306th Psychological Operations Battalion, Los Alamitos, California; Headquarter Commandant, 63rd Army Reserve Command, Los Alamitos, California; Commander, 377th Personnel & Administration Battalion, 63rd Army Reserve Command, Long Beach, California; Chief, Unit Training Division, 63rd Army Reserve Command, Los Alamitos, California; and Assistant Chief of Staff, Personnel, 311th Corps Support Command, Los Angles, California.

His military education consists of: Infantry Officer School, Jungle Operations Course, Infantry Officer Advanced Course, and Command and General Staff College.

His military awards include: Bronze Star Medal, Meritorious Service Medal (2nd Award), Army Commendation Medal (3rd Award), Army Achievement Medal, Vietnamese Cross of Gallantry with a Bronze Star and Combat Infantryman Badge.