In WWII, a US Army division was 20,000 men, at full strenght. Most european armies preferred smaller divisions-usually 10,000 men, or half the US Army size.
Anybody know why the US preferred larger divisions?
Different TOE=Table of organisation and equipment. US divisions usually had a lot of support units and formations attached; for example an three artillery battalions, ususally one anti-aircraft battalion, a tank battalion, as well as signals, engineers and medical bns.
British divisions were often bigger, but usually British divisions were HQ, with as many battalions attached as possible, in Burma the 36th (Ulster) Division had at one point 37 battalions attached, though this was for a short period.
It might very well be that the US preferred to set each division up as almost a self-contained army, with a full set of organic support units, whereas the Europeans historically preferred to have pure e.g. infantry divisions or cavalry divisions and bolt on batallions/regiments/brigades of supporting arms (e.g. artillery, engineers, etc.) if they are required for a mission. FWIW, the US tendency to ‘supersize’ divisions goes back at least to WW1, when the European powers were startled by the size of the US divisions deploying on the western front.
It is simply a national trait.
We first had divisions in the Civl War. Each was nominally three regiments. This was continued when divisions were formed for WWI. We have had divisions ever since.
So, American divisions are bigger (about twice the size) than European ones because our regiments are bigger. Our regiments are bigger because they were expected to fight the Indians on long, remote campaigns with little or no outside assistance.
American regiments were self-contained since Way Back. A division is sometimes said to be the smallest self-contained unit. When you take three self-contained regiments and make a division out of them, you end up with an oversized division.
Was that helpful?
And sometimes a Marine Corps MEU (Marine Expeditionary Unit) is said to be the smallest. You left off the “in the Army.” part of that sentence.
A MEU has about 2,200 jarheads, composed of a reinforced infantry battalion (with LAVs, tracks), composite squadron (helos, Harriers), and a support group. It is not a permanently organized unit, but stands down and rebuilds on a regular basis with rotating units taking the roles.
But you knew that.
Incidentally, this question has been asked often within the Pentagon for over a decade. There are lots of folks pushing to make the military more maneuverable by chopping it into smaller chunks. It’s extraordinarily difficult to change since it would necessitate so much shifting of command chains. You can easily imagine petty rivalries and turf wars emerging as a result of transfers of power.
Nonetheless, they’re moving towards that goal, slowly but surely. The Army Transformation project has a goal of refocusing Army resources to be more brigade-centric and less division-centric.
All of this stuff has deep historic roots.
A Corps was supposed to be able to fight on its own for a day. (In Napoleon’s time.) Another way to say it is that a corps had formations of all the combat arms.
A division was supposed to be the smallest self-contained combat unit. It had its own surgeon, smithy and whatnot, but had only one combat arm.
A brigade was three regiments (in the Civil War era) but came to mean a combat-team based on a regiment by WW2 or so.
A regiment was a single-arm, usually based in (or recruited in) a unique geographical area.
None of that is true any more. In the movern US military, a division has all (well most) of the combat arms organic, a regiment (in the cav) is like a small division.
The brigade is now the same as a regiment. The regiment (outside the cav) has lost all tactical relevance and is an historical fig leaf.
So, in the US at least, read one echelon up to get an idea of combat power. “Division” is more like a “Corps” elsewhere.
(Oddly doctrine requires you fight two up. Platoons kill battalions, Battalions take on enemy divisions.)