Colonel Brennan enlisted, from Bedford, Texas, in May 1997, serving with Marine Aircraft Group 41, 4th Marine Aircraft Wing. He commissioned through the Platoon Leaders Course (combined) upon graduating from Texas A&M University in December of 1998.
Assignments include Marine Fighter Attack Squadron 251, Carrier Air Group 1, Marine Aircraft Group 31. Marine Fighter Attack Squadron 112, Marine Aircraft Group 41. Marine Fighter Attack Squadron 323, Marine Aircraft Group 11. Carrier Air Group 11, Carrier Strike Group 11. Commanding Officer Marine Fighter Attack Squadron 122, Marine Aircraft Group 31. Commanding Officer Marine Aircraft Group 41, 4th Marine Aircraft Wing.
Staff Assignments include Administration Officer, Quality Assurance Officer, and Family Readiness Officer, Marine Fighter Attack Squadron 251, where he deployed in support of the Unit Deployment Program (2003), and with Carrier Air Group 1 in support of Operation Enduring Freedom and Operation Iraqi Freedom (2005) Director of Safety and Standardization, Pilot Training Officer, Weapons and Tactics Instructor, and Operations Officer, Marine Fighter Attack Squadron 112, where he deployed to Al Asad, Iraq, Operation Iraqi Freedom (2009). Operations Officer, Aircraft Maintenance Officer, and Executive Officer, Marine Fighter Attack Squadron 323, where he deployed with Carrier Air Group 11 in support of Operation Enduring Freedom (2013), and the Unit Deployment Program (2015). Operations Officer, Carrier Air Group 11, deployed in support of Operation Enduring Freedom. Tac-Air Integration, and F/A-18 Requirements Officer, Deputy Commandant of Aviation. Executive Officer Marine Aircraft Group 31. Assistant Chief of Staff G-3, 3d Marine Expeditionary Brigade / Task Force 76/3, Camp Courtney, Okinawa, Japan. He is currently assigned as the Chief of Staff Marine Forces Reserve.
Joint Assignments include Joint Operations Center Team Chief, Central Command. Presidential Nuclear Strike Advisor / Assistant Deputy Director of Operations, Operations Team 4, National Military Command Center.
Colonel Brennan’s military education includes Amphibious Warfare School (non-resident) Weapons and Tactics Instructors Course, MAWTS-1, Air Command and Staff College (resident), and Top-Level School at the Marine Corps War College.
Colonel Brennan holds a Bachelor of Environmental Design (Architecture) from Texas A&M University; Master of Military Science and Operational Design from Air Command and Staff College; and a Master of Strategic Studies from the Marine Corps War College.