Dr. Mountcastle is a 1994 graduate of the Virginia Military Institute and holds a Masters and PhD in History from Duke University.  He served as an officer and historian in the U. S. Army for more than two decades. His military service took him to Germany, South Korea and Iraq and on assignments with the 82nd Airborne Division, US Army 5th Corps and US Army Special Operations Command.   He taught military history at West Point and led the development of the military history curriculum at the US Army Combat Studies Institute at Fort Leavenworth.  More recently, he served as the Professor of Military History at the University of Washington in Seattle and as an Assistant Professor of Military History at the US Army Command and General Staff College at Fort Lee, Virginia. Following his retirement from active duty with the U. S. Army, he returned to the Old Dominion and was appointed Director of the Virginia War Memorial in Richmond in June 2016.

He and his wife, Dr. Sally Mountcastle, and their three children live in Chesterfield County, Virginia.