I'll do these posts as I work through the scenario, proportioned for a smaller miniature army that is functionally possible to use in a reasonable length game.
A quick look at a map shows that the length of the Gettysburg field, from roughly the end of Little Round Top to the other end at Cemetery Hill is around 7000 yards. I haven't decided if the first day's battle will be included or not. For this exercise, I'll just use the 7000 yard figure.
My table is 108" ( 9 foot). So - 7000 yards/ 108" = 64.8 yards per inch. I'm comfortable enough with my historicity to round that up to 1" = 65 yards. My preferred set of rules is Field of Battle, 2nd Edition. FoB's nominal ground scale is 1" = 25 yards. The actual to game ground scale ration is 65/25, or 2.6. I'm happy to say that the real to game ground scale is somewhere around 2.5 to 3 to 1.
So, this begins to tell us what kind of game proportioning (real units to game units) we'll see. If we assume the same 2.5 to 3 to 1 scaling, we can start to see where we are.
Assume that the game unit is the game representation of the nucleus of the multiple units it represents. The multiple real units would be deployed "somewhere" around that game unit nucleus, with 2.5 to 3 times the frontage. This means we'd also have more depth than the nucleus game unit. So, if we make another assumption (never assume, or it will make an....), and say that we have something like a box of 2.5 to 3 real units wide by 2.5 to 3 real units deep roughly centered around our game nucleus unit, that means that the game unit represents something like 6.25 to 9 real units. I can live with rounding that and saying 1 game unit = 6 to 9 real units.
At the least detailed OOB level, the Army of the Potomac had around 93,000 men. The Army of Northern Virginia had around 73,000 men. Let's assume, for the sake of conversation, that the infantry present for battle (leaving out cavalry and artillery) represents around 60% of those numbers. That leaves us with around 55,000 for the AoP and 45,000 for the ANV. If we take that further, and assume that each infantry regiment is 500 men, then the AoP has 110 regiments and the ANV has 90 regiments. Are these numbers correct? I don't know. I have plenty of resources to acurrately figure this out, but quite honestly, this is for a game, not a dissertation and I just don't want to go to that level of research!
So, if you're still following along, we were looking at 1 game unit equaling 6 to 9 real units. That means that the AoP would be 110/6 to 110/9 infantry units, or somewhere between 12 and 18 infantry (game) units. Similarly, the ANV would be somewhere between 10 to 15 game units.
My ACW collection (25mm) presently has 15 Federal infantry regiments in it. Zowie! 15 units is right in the middle of the 12 to 18 unit range we're looking at above. If I follow proportions, the ANV would then have 12 infantry units or so for the game.
What does each game unit represent? Surely at the extremes, a very large brigade to a division of real troops. Does that change the game? Not in the least.
Next will be a scaling of support units (cavalry and artillery) to get that correct.
This is actually quite a bit of fun! Now its back to the painting table to work on Libyan spear units for my Carthaginian army (Pulse of Battle).