Marine Expeditionary Unit. The smallest type of Marine Air Ground Task Force. A principal United States Marine Corps organization that combines air-, land-, and sea-borne forces to conduct a wide array of military operations and humanitarian responses anywhere in the world. Comprised of a CE, ACE, GCE, and LCE. May take the form of a MEB, MEF, or MEU. with customizable composition based on the task at hand. Additional artillery, armor, or air units can be attached, including squadrons of MV-22B Osprey and AV-8B Harriers.