The I Marine Expeditionary Force (pronounced as first) is a Marine Air Ground Task Force (MAGTF) of the United States Marine Corps primarily composed of the 1st Marine Division, 3rd Marine Air Wing, and 1st Marine Logistics Group. Among Marines, it is common to pronounce I MEF as "eye mef", "first mef", or "one mef". Image:Stub.png. You can help My English Wiki by expanding it.