Colonel Cornelius Breen was commissioned an Infantry Officer upon graduation from Officer Candidate School 20 August 1942, class number 53. His first duty assignment was as Platoon Leader, Company C, 3d Infantry, New Foundland. | His subsequent duty assignment include: Company Executive Officer, Headquarters, Newfoundland Base Command, 471st Infantry Battalion; Post Commander and Post XO, Headquarters Fort McAndrew; Aerial Port Officer and Squadron Adjutant, Westover Air Force Base, ATC; CI Agent duties, 108th Counterintelligence Detachment, New York City, New York; S-3, 108th CO Det, NYC; Commander, CIC Det in combat, 209th CIC Det, Korea; Commandant CIC School Far East, 441st CIC Det, Japan; School Secretary, DA Strategic Intel School, Washington , D.C.; Deputy Battalion Commander/ Commander/ Battalion Commander, 163 Military Intelligence Battalion, SETAF, Verona, Italy; Chief Security Military Intel Branch, Headquarters USCONARC, Fort Monroe, Virginia. | His awards and decorations include: Army Commendation Medal (with Oak Leaf Cluster), Bronze Star Medal, Legion of Merit.