I Marine Expeditionary Force (I MEF)

Organization and principal units

A MAGTF like I MEF integrates three core elements so it can operate independently or as part of a larger joint force:

• Ground combat element: the 1st Marine Division, responsible for infantry, armor, artillery and combat support.
• Aviation combat element: the 3rd Marine Aircraft Wing, which provides fixed‑ and rotary‑wing aviation, close air support and air reconnaissance.
• Logistics combat element: the 1st Marine Logistics Group, delivering supply, maintenance, transportation, and medical services.

These elements allow I MEF to form task-organized units ranging from a Marine Expeditionary Unit (MEU) to larger Marine Expeditionary Brigades (MEBs) and the full MEF.

History and operational role

I MEF traces its organizational model to the post‑World War II development of the MAGTF concept and has participated in major operations and contingencies where Marine Corps expeditionary forces were employed. As the largest of the Marine Corps’ three MEFs, it has been involved in regional training, amphibious exercises, humanitarian missions and combat deployments, supporting joint and coalition operations across the Pacific, Middle East and elsewhere.

Capabilities and typical missions

• Amphibious assault and forcible entry operations
• Air-ground maneuver and close air support
• Logistics sustainment and casualty evacuation
• Noncombatant evacuation, disaster relief and security cooperation

I MEF is often described as a "warfighting" MEF because of its focus on readiness for major combat operations. For more information about MAGTF organization see the Marine Corps overview, and for base information visit Marine Corps Base Camp Pendleton.