Dr. Callahan is the Director of History Division. He was commissioned into the Marine Corps in 1992 after graduating from the U.S. Naval Academy.
He served on active duty for 22 years as an F/A-18D Weapons and Sensors Officer with deployments to Europe, the Western Pacific, and the Middle East. During his military career he also served as a Forward Air Controller, commanded two headquarters units, and started a second career path in education.
His teaching assignments included instructing in the History Department of the U.S. Naval Academy and as a Faculty Advisor at the U.S. Marine Corps Command and Staff College. Dr. Callahan also served as an adjunct faculty member for the Expeditionary Warfare School and Command and Staff College Distance Education Programs (EWSDEP and CSCDEP).
He retired from the Marine Corps in August 2014 as a lieutenant colonel and was then employed as the Course Director for the CSCDEP Theory and Nature of War course for the next nine years. Dr. Callahan joined the Marine Corps History Division in his current role as its director in January 2024.
He earned a Ph.D. in History at the University of Maryland in 2023, dissertating on the theories of John Boyd, the origins of maneuver warfare doctrine, and doctrinal change within the Marine Corps after the Vietnam War.