Rear Admiral Mattis, from Fullerton, CA, graduated with distinction from the United States Naval Academy, Annapolis, MD in 1994 and Oxford University, England in 1996 as a FitzGerald Scholar. At sea, Mattis qualified in submarines, as a nuclear engineer and as a ballistic missile officer while serving on USS HENRY M. JACKSON (SSBN 730)(GOLD). He also deployed aboard USS ALABAMA (SSBN 731)(GOLD) and USS COLUMBUS (SSN 762) during his Junior Officer tour from 1998-2000. Ashore, Mattis served on the staff of the Chief of Naval Operations, Washington, DC as an Assistant for Political-Military Affairs in 1994 and at the Naval Satellite Operations Center (NAVSOC), Point Mugu, CA from 2000-2002 as Satellite Operations Department Head and later Operations Director (N3/5/6). He transitioned to the Navy Reserve in 2003.

In the Navy Reserve, Mattis’ command tours include: Post-Major Command as Deputy Commander, NR Readiness and Mobilization Command (REDCOM) San Diego, NR Naval Information Warfare Systems Command (NAVWAR) Space and Unmanned Systems West, NR Commander, THIRD Fleet (C3F) Headquarters (HQ), and NR Undersea Warfare Detachment, Salt Lake City. He also served at NR Undersea Warfare Operations Detachment Port Hueneme as Chief Staff Officer and as the Submarine Force Reserve Component Operational Planning Competency Lead, NR Naval Mine and Anti-Submarine Warfare Command (NMAWC) as Executive Officer, Operations Officer and Administrative Officer, and Space and Naval Warfare Systems Command (SPAWAR) 0466 as Operations Officer.

Returning to Active Duty in 2008-2009, Mattis, trained in Army Civil Affairs and deployed to Baghdad, Iraq as part of Operation Iraqi Freedom (OIF) in support of the XVIII Airborne Corps/Multi-National Corps-Iraq (MNC-I) serving as MNC-I C9 (Civil Military Operations) Effects Assessment Officer, working as an Operational Level of War (OLW) planner for Non-Kinetic Effects, evaluating civil capacity across Iraq and coordinating assessments with the Department of State Office. In 2020 Mattis returned to Active Duty supporting OPNAV N7 as the Space, Information Warfare and Integrated Fires Lead for the Tri-Service Maritime Strategy and led COVID-19 relief efforts in Los Angeles (LA) as the shore OIC and later
Commander, Task Force-LA. He returned to Active Duty again in 2021-2022, serving as Director, Navy Space Command (NAVSPACE), leading the stand-up of NAVSPACE as the Navy Service Component to US Space Command (USSPACECOM). Mattis assumed his current roles as Director, Strategic Effects for Commander U.S. Naval Forces Europe/Africa and Commander, CTF-66 in October 2023.

Mattis’ awards include the Legion of Merit (3), Bronze Star Medal, and Meritorious Service Medal (4). He is a graduate of USMC Command and Staff College and Joint Forces Staff College Joint Professional Military Education programs, National Defense University Reserve Component National Security Course, Naval War College Executive Level OLW Course and Naval Postgraduate School Navy Senior Leader Seminar. He is a Joint Qualified Officer and qualified as an Information Warfare (Space Cadre) Officer.