Colonel Robert William O’Brian was commissioned an Infantry Officer upon graduation from Officer Candidate School in March of 1967. His first duty assignment was as an Instructor at the Mountain Range Camp. | His subsequent duty assignments include: Platoon Leader, 173d Airborne Brigade: Advisor Team 31, Republic of Vietnam; Range Control Officer, Fort Devens, Massachusetts; S3, 3/18th Infantry Brigade, Lowell, Massachusetts; Company Commander, CSC 3/18th Infantry Brigade, 187th Infantry Brigade; S3, 3/18th Infantry, 187th Infantry Brigade; Logistical Service Officer, 187th Infantry Brigade; Individual Ready Reservist; Chief, Plans and Operations, Headquarters, 94th U.S. Army Reserve Command; Assistant S-3, 187th Infantry Brigade: S3, 187th Infantry Brigade; Battalion Commander, 3/18th Infantry Brigade; Chief Individual Training, Headquarters and Headquarters Detachment, 94th U.S. Army Reserve Command; Deputy Brigade Commander, 187th Infantry Brigade, Fort Devens, Massachusetts.