How Are Army Divisions Numbered?

Here's a few rules of thumb regarding heirarchal organization of military units,...at least in the US since WWI.

Theory of Threes:
Any unit with a leader overseeing less than three will tend towards micromanagement, while any leader in charge of more than three will tend towards either regrouping his assets into 3 managable entities or will loosen control on his command. With this stated, here is the general heirarchal organization of US military for ground forces.

In each of these groupings, additions or deletions may arise to match the intent of the unit.

3 men = Fire team
3 Fire Teams = Squad
3 Squads = Platoon
3 Platoons = Company
3 Companies = Battalion (smallest deployable force)
3 Battalions = Regiment
3 Regiments = Division
3 Divisions = Corps
3 Corps = Army
3 Armies = Front

This is the general theme. Now in practice, over time, there are numerous variations. E.G.

3 Men + Fire Team Leader or 4 Men = 1 squad
3 FT + Sqd Ldr = 1 Squad
3 Sqds + Plt Sgt, Plt Guide, PltCO = 1 Plt
3 Plts + CoHQ, Co 1stSgt, CoCO, COXO, etc = 1 Co
3 Cos + WpnsCo, HQCo, BnCO, SgtMaj, etc = 1 Bn
3 Bn + RegtHQ, = 1 Regt
etc

Now over time these might change at various levels,...again this is only focused on infantry as the model...in the US. specifically the Marine Corps.

Now consider how deployed units which are 'TASK-ORGANIZED'.

A MAGTF (Marine Air-Ground Task Force) is composed of 3 Elements led by a Command Element (4 elements).

GCE = Ground Combat Element
ACE = Air Combat Element
CSSE = Combat Service Support Element
CE = Command Element

A MEF, (Marine Expeditionary Force) corresponds to Division sized elements. E.g.
1 Marine Division (grunts) + 1 Marine Wing (Fixed and helo aviators) + 1 FSSG (Division sized support element, maintenance, supply, etc) + 1 MEF Command Element = 1 MEF

A MEB (Marine Expiditionary Brigade) is simlar to the MEF, only based upon regimental sized elements.

1 Marine Regiment + 1 Marine Composite Group (2-3 squadrons) + 1 Marine CSSG + MEB HQ (Which no longer exist but are now called MEF Fowards depending on time and place and task organization of the remainder of forces..go figure)

A MEU Marine Expeditionary Unit is similar to the MEF, but based upon Battalion sized elements. e.g.

1 Battalion + 1 Composite Squadron + 1 CSSE + MEU HQ = 1 MEU

Now consider how these structures may change over time, equipment and tactics, keeping with task organized structures.

The Marine Corps does refer to a Brigade, essentially, the regimental sized MAGTF based in Hawaii.

Number systems are kept fairly simple. odd number -west coast, evens-east coast (not quite, but easier to remember) and the bastard stepchildren in Okinawa.

1st MarDiv = 1,5,7 Regts (grunts)
2nd MarDiv = 2,4,6 Regts
3rd MarDiv = 3,8,9 Regts (I might be off here a bit) with one of those regts assigned to the Brigade in Hawaii.

Now this basis changes with time, politics, funding, tactics, etc.

For example, ever since WWII, it seems that every 7 years the trucks assigned to grunts are switched between a separate Battalion within the Division to direct assignment as a company to the battalions to a separate battalion within the FSSG. Depends on leadership and the situation.

Fire Teams and Squads.
When the USMC is procuring weapons or personnel, these units might vary a bit so they can procure the weaponry with justification and then later reorganize if times gets lean. Instead of a Rifleman, Grenadier and Automatic Rifleman and fire team leader, the squad might reorganize 3 FTs into 2 larger fireteams and associated support weapons.

TOWs might swap between Tank Bns and Regt HQs.
so
If 2 tanks = section
2 sections = Plt
and 3 Plts = Co,
What do 5 TOWs make?

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