Colonel Sean M. Castilla

Col. Sean Castilla assumed his present duty as a U.S. Army War College Fellow at The University of Texas in July 2026. He is from McAllen, Texas. He commissioned as an Armor officer in the U.S. Army in May of 2006 from the ROTC program at St. Mary’s University.

Prior to his fellowship, Col. Castilla served at U.S. Southern Command (USSOUTHCOM) in Doral, Florida, as Chief of the J39 Division for Information Operations and as a Planner in the J35 Future Operations Division.

Col. Castilla commanded the 3rd Battalion, 8th Cavalry Regiment located in Ft. Hood, TX and during that time he dual-hatted as the Commander of the Enhanced Forward Presence Battle Group – Poland while deployed to Poland. He also commanded C Company, 2nd Battalion, 5th Cavalry located in Ft. Hood, TX.

His staff assignments include service as a battalion and brigade Operations Officer in the 1st Armored Division, Armor Branch Career Manager at U.S. Army Human Resources Command, and Lead Exercise Planner at U.S. Army Joint Modernization Command. At the strategic level, he served as Deputy Strategist in the Office of the Chief of Public Affairs, East Africa Desk Officer in the Office of the Secretary of Defense for Policy, and Aide-de-Camp to the Commander of the U.S. Special Operations Command Africa. He began his service as a Reconnaissance Platoon Leader in the 101st Airborne Division (Air Assault).

Col. Castilla’s deployments include Iraq, Kuwait, South Korea, and Poland. His decorations include the Bronze Star Medal, Purple Heart, Defense Meritorious Service Medal (with Bronze Oak Leaf Cluster), Meritorious Service Medal (with Silver Oak Leaf Cluster), Joint Service Commendation Medal, Combat Action Badge, Ranger Tab, Parachutist Badge, Air Assault Badge, Pathfinder Badge, Office of the Secretary of Defense Identification Badge, and the Army Staff Identification Badge.

Col. Castilla holds a Bachelor’s Degree in Psychology from The University of Texas, a Master’s Degree in International Relations from St. Mary’s University in San Antonio, and a Master’s Degree in Public Policy from Georgetown University.

Col. Castilla is married to the former Theresa Hill of Menard, TX and together they have three children: Joshua (13), Margaret (10), and Jude (8).