A graduate of the U.S. Military Academy at West Point, Colonel Farrell served as an armor officer in a variety of leadership assignments in the United States, Europe, and the Middle East. He has led American soldiers in three different wars, including as an advisor to the Afghan National Army in Afghanistan and as the battalion commander of a 1,000-soldier combined arms battalion conducting extended combat operations in East Baghdad, Iraq. His most recent military assignment was Chief of Military History at the U.S. Military Academy at West Point.

His military decorations include the Legion of Merit, the Bronze Star, and the Combat Action Badge. Colonel Farrell holds the M.A., the M.Phil, and the Ph.D. from Columbia University in New York City. A recognized international authority on leadership and military history, he has been featured frequently on the History Channel and PBS while his most recent book is The Military and the Monarchy.