That's an interesting question in a lot of ways. There are a lot of things that make the wargamer's idealized OBs and TOEs a matter of fiction. But at the same time it is a fiction we must embrace. Unlike computer games, or boardgames, or even the original Kriegspiel where units can be subdivided as much a suits, miniatures have a certain size that makes it hard to break down units beyond a minimum granularity.
But so be it. I have already pretty much decided that the lowest level of commander for a multi-player game is the corps commander, and in 1870 for both armies the building blocks of corps are divisions. The way they corps are built is very different between the French and Prussian armies, but that is another post. I'll set the Cavalry divisions aside for now as well.
On the French side, a "typical" infantry division is more or less 2 brigades, each of 2 regiments of line (with the 1st brigade having a battalion of Chasseurs as well a bonus) plus 2 batteries of field guns and a battery of Mitrailleuse. Since a French battalion is 750 men at full strength, that gives line regiments of 2250, and brigades of 4500-5250.
More of less, give and take. Units can be below strength to varying degrees, battalions can be detached, battalions can be attached -- all of these things I may want, or need, to consider at some point.
Before I get into the German formations, I shoudl make it clear that I am starting with the Prussian practice, before looking at the rest of the North German Confederation, and then at the various South German allied states. Although the Prussians were more-or-less the models the other states were moving toward, in 1870 the integration was not complete and German practice in general is not exactly always the Prussian model.
The Prussian infantry division is a bit more complicated. It likewise has 2 brigades each of 3 regiments. The regiments, however, are made of 3 x 1000 man battalions. The Brigade therefore is 6000 men at full strength. While each French division has a battalion of Chasseurs, Prussian Jaegers are a corps asset, so one may or may not be attached to a division.
The artillery firepower is far greater, with 2 batteries of Krupp lights, and 2 of heavies. In addition, a 600-saber regiment of cavalry was integrated with the division.
This means our Prussian division at paper bayonet strength is nearly 25% larger than its French opposite number, setting aside supporting arms.
So, how to represent this?
There are several ways to go, each with it's own advantages and disadvantages.
The simplest is "a stand is a division" - nice big stand, all types of figure on it.
For the next level there is a split. We can take a uniform stand size and figure count and say "this is so many thousand men" -- So if we take 3000 per stand, a Prussian division gets 4, a French 3 and Bob's your uncle.
The problem with this is that it cannot map any historical designation by the stand for both sides. At a stand equals 3000, each stand lines up nicely with a Prussian regiment, but a French brigade is a stand-and-a-half. At 2000 men each, the French Regiments sort out nicely, but a Prussian regiment becomes a stand-and-a -half.
Is that a problem? If we are just talking about the Division and the stands are just representing states and formations within it, this should be no worse than the common practice or representing a lace wars battalion as several stands and ignoring the platoon or company organization within it.
You can tell I am waffling on this issue.
The alternative is to have each stand represent a fixed formation - say a French or Prussian regiment -- and have the difference in size represent in the base size and factors. Then I can say "That stand is the 2nd Turco Regiment, 2nd Brigade, 3rd Division." This is especially nice for the French, with their fancy uniforms.
At the moment, I am not going to worry about the Brigades of the Army of the Loire, which paired a Regiment De Marche with a regiment of Guarde National Mobiles in each of its brigades.
Except perhaps to consider it simplest to break a division up into either 4-6 2000 man stands or 3-4 3000 man stands.
the larger number reduces the number of stands, making it easier to make the time objective. The smaller lines up with the French regiments for the sake of the pretty uniforms, and make the stand or that pesky 600-man attached cavalry regiment a bit more beefy in its figure count.
In the next post, I will try to fit cavalry into this picture.
update: Ive been kicking this around a lot. Here's the July 2012 iteration.