Colonel Donald L. Keldsen was commissioned an Infantry Officer upon graduation from Officer Candidate School, 26 January 1967. His first duty assignment was A Detachment Commander, Company C, 7th Special Forces Group (Airborne), Fort Bragg, North Carolina. | His subsequent duty assignments include: Platoon Leader, Bravo Company, 2nd Battalion 12th Cavalry, 1st Cavalry Division (Airmobile), Vietnam; Operations Officer, H Company, 52nd Infantry (Long Range Recon Patrol), 1st Cavalry Division (Airmobile), Vietnam; Company Commander, Headquarters Company, 6th Special Forces Group (Airborne), Fort Bragg, North Carolina; A Detachment Commander, 46th Special Forces Company (Airborne), Thailand; Company Commander, Combat Support Company, 1st Battalion, 35th Infantry, 25th Infantry Division, Schofield Barracks, Hawaii; Human Relations Officer, 2nd Brigade, 25th Infantry Division, Schofield Barracks, Hawaii; Chief, Organizational Effectiveness Branch, First U.S. Army, Fort Meade, Maryland; Battalion Executive Officer, 7th Infantry Division (Light), Fort Ord, California; Curriculum Evaluator Command and General Staff College, Fort Leavenworth, Kansas; Chief, Integrated Development Plans, Combined Arms Center, Fort Leavenworth, Kansas; Group Executive Officer, 10th Special Forces Group (Airborne), Fort Devens, Massachusetts; Battalion Commander, 10th Special Forces Group (Airborne), Fort Devens, Massachusetts; Director, Personnel, Administration and Security, US Delegation to North Atlantic Treaty Organization Military Committee, Brussels, Belgium and Senior Army Advisor to the Maryland Army National Guard, Baltimore, Maryland. | Following retirement Colonel Keldsen worked as a Senior Consultant, Human Equations, Inc. in Baltimore, Maryland.