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I MEF provides the Marine Corps a globally responsive, expeditionary, and fully scalable Marine Air-Ground Task Force (MAGTF), capable of generating, deploying, and employing ready forces and formations for crisis response, forward presence, major combat operations, and campaigns. 


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Sailors, Marines to conduct Maritime Prepositioning Force exercise off coast of San Diego

6 Oct 2014 | 1st Marine Expeditionary Force Public Affairs Office

U.S. Navy and Marine Corps expeditionary forces are scheduled to participate in a Maritime Prepositioning Force (MPF) exercise, Exercise Pacific Horizon 2015, off of the coast of Southern California and ashore at Marine Corps Base Camp Pendleton, Oct. 20-28, 2014.

Pacific Horizon is a scenario-driven Humanitarian Assistance/Disaster Relief exercise designed to train the U.S. Navy and Marine Corps in MPF operations. The exercise will test staffs in the planning and execution of MPF operations, civil-military security assistance, and infrastructure renovations in a series of live and constructive training events. Exercises like PH15 provide realistic, relevant training necessary for effective global crisis response expected of the Navy and Marine Corps.

Units from U.S. Third Fleet's Expeditionary Strike Group 3 and 1st Marine Expeditionary Brigade will employ the latest technologies and operational techniques to accomplish PH15 training objectives. This exercise will involve ship to shore off-loads of equipment and humanitarian resources as well as disaster relief and ground security operations.

PH15 participants include U.S. Navy Expeditionary Strike Group 3 (ESG-3) command element, 1st Marine Expeditionary Brigade (1st MEB) command element and the following composited forces: USNS MONTFORT POINT (Mobile Landing Platform, MLP-1), USNS DAHL (LMSR), USNS WILLIAMS (T-AK), Naval Beach Group One (NBG-1), Amphibious Construction Battalion One (ACB-1) , Beach Master Unit One (BMU-1), Assault Craft Unit One (ACU-1), Assault Craft Unit Five (ACU-5), Marine Wing Support Squadron 373 (MWSS-373), Combat Logistics Regiment 1 (CLR-1), and 1st Battalion, 4th Marines (1/4).

Between the exercise dates Oct. 20-28, local San Diego residents may notice an increased presence of naval vessels and maritime activity off the coast of Camp Pendleton. 

On Frid, Oct. 24, ESG-3/1stMEB PA will host a Media Day that includes interviews with key Navy and Marine Corps leadership as well as coverage of sea-based, ship to shore, and humanitarian response activities.  Media interested in covering the exercise should contact Maj. Staci Reidinger, 1st MEB public affairs officer at (760) 277-7823 or staci.reidinger@usmc.mil.

Expeditionary Strike Group 3 mission: Through aggressive training and readiness, Expeditionary Strike Group Three provides regional and combatant commanders with an agile, tailorable, forward-postured and immediately employable force, capable of projecting expeditionary striking power in the maritime, littoral, and inland environs in support of U.S. national interests.

1st Marine Expeditionary Brigade mission: When directed, 1st Marine Expeditionary Brigade composites and deploys as a Marine Air Ground Task Force (MAGTF) in support of Combatant Commander (COCOM) requirements across the range of military operations.  With appropriate augmentation, 1st MEB prepares and deploys combat ready MAGTF's to support COCOM presence and crisis response; and supports service and COCOM initiatives as required.

Coordinating Instructions:  Media interested in covering Pacific Horizon 2015 must RSVP attendance by October 16 via email to staci.reidinger@usmc.mil.  Confirmed media will be provided an itinerary of events for Media Day (Oct. 24) which is scheduled to include a visit to one of the Navy's newest vessels and viewing of ship to shore operations.

View complete press release

I MEF Leaders

George W. Smith Jr.
Commanding General, I Marine Expeditionary Force

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Brig. Gen. Ryan S. “Chick” Rideout
Deputy Commanding General, I Marine Expeditionary Force

Brigadier General Rideout assumed duties as Deputy Commanding General, I Marine Expeditionary Force in July 2021. His previous assignment was serving as Director, Military Advisor Group, Combined Joint Task Force - Operation INHERENT RESOLVE based in Baghdad, Iraq from June of 2020 to June 2021. Fleet Marine Force assignments include: Commanding

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Colonel Brian Rideout
Chief of Staff, I Marine Expeditionary Force

Colonel Rideout holds a baccalaureate degree in Psychology from Ohio Wesleyan University, a Master of Science in Information Technology Management from the Naval Postgraduate School, a Master of Military Studies from Marine Corps University and a Master of Arts in National Security and Strategic Studies from the Naval War College.  He is a graduate

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Sgt. Maj. Terrence C. Whitcomb
Sergeant Major, I Marine Expeditionary Force

Sergeant Major Whitcomb began Marine Corps Recruit Training on 14 September 1993 at Marine Corps Recruit Depot, San Diego, California with Company C, 1st Recruit Training Battalion.  He was meritoriously promoted to Private First Class and graduated Recruit Training on 10 December 1993. Following graduation from Recruit Training, Private First

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Command Master Chief

 Though a native of Montebello, California, Master Chief Ruiz calls Monte Vista, Colorado home.  He enlisted in the Navy in March 1991, reported to basic training at RTC Great Lakes, Illinois and completed Signalman “A” School at NTC Orlando, Florida.  After serving two tours as a collateral-duty Command Career Counselor in 2000 and 2003, he became

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