I saw that one of the groups of soldiers fighting in Iraq was labeled as an expeditionary force. What is different about them? Why aren’t they just the 5th Armored Division or the 8th Cavalry Division (joke) or whatever? Honestly, calling them an expeditionary force makes it sound like they’re less important.
Q: “You here to fight?”
A: “Naw, we’re an expeditionary force. We’re on an expedition!”
It’s a particular type of unit unique to the US Marine Corps, a Marine Expeditionary Force (MEF). It’s generally a Marine division with extensive additional supporting arms.
This website has more details, but also some very annoying adverts.
Nope, not unique tothe Marines. It’s a military concept developed in the mid 90s in an effort to “spread the wealth” or the responsibility for deploymetns to forward locations. Prior to that time the taskers to deploy were sent to the closest Major Comand and therefore the bases within that command got hit repeatedly to deploy while some fo the others rarely went. Now someone in the great DoD pie-in-the-sky decides how many bodies they need to function at that particular forward location and the tasker to fill those slots are rotated through out any deployable base. However with the defense posture what it is right now I think there are a whole lot of forward deployed bases.
Really? I didn’t know; I’d only seen MEF specifically relating to, well, the “M” part. Thanks.
Yeah, I work for the Air Force and for us it’s AEF. 
Truthfully, I didn’t know the Marines did the same thing but it does make sense that it would be DoD wide. Is it roughly the same concept?
Eh, I’m no expert. Non-military, not even US. There are far more qualified Dopers here than I to talk in detail about it, I’m sure. I’m just a bit of a know-it-all show-off who doesn’t know when to shut up!
The MEF is the largest and most powerful of the MAGTFs and is the principal warfighting MAGTF in the active force structure. It consists of a command element, Marine aircraft wing, Marine division and a force service support group.
ref: Marine Corps Common Skills Handbook
I always took it to be a large force fighting overseas. In WW1 and WW2 , The troops sent to Europe(likely elsewhere as well) were called the American Expeditionary Force(AEF). The British have been sending expeditionary forces all over for a long time.
I was sure I’d heard earlier uses, and the first result on Google mentions a Canadian expeditionary force in WWI. Your explanation of what it is might still be correct, but it doesn’t really explain why it’s called “expeditionary”. Anyone?
Expeditionary refers to being able to pick up and move in a very short time period. The EAF (exp. air field) here in 29 Palms is called that due to it not being a permanent air field, and if need be, it could pick up and relocate.
As in ‘Good heavens, the volcano is erupting/penguins are attacking/dark-skinned persons want to have a word about the burial site we excavated, run for it, no time to stop and pack’? Yeah, I suppose that sounds reasonable.
Like in Roadrunner cartoons, or Roger Rabbit, when they pick up the road and drag it off to the side? Wow! 
Do you have any of that hole paint too?
The British created the British Expeditionary Army after the Boer War. By the end of WWI, it had been divided into the First, Second, Third and Fourth Armies.
The Canadian Expeditionary Force had more than 600,000 soldiers during the First World War.
Ahh, got it, so the AF adopted it in the mid-90s but it isn’t a new concept. Still I think that is pretty much what it signifies. It’s a fancy-schmancy way to say they are deployed and not permanent partry personnel. Right?
Before they were called Marine Expeditionary Forces/Brigades/Units they were called Marine Amphibious F/B/U’s, or MAF, MAB, and MAU. They changed them to the existing name in 1988.
Something that makes them unique in the Marine Corps is that in the smallest unit, the MEU, you have a reinforced infantry battalion, a composite helicopter squadron (with Harriers) and a Service Support Group all under one commander, a full Colonel.