[reviewed/revised 19 Oct 2021]
The Brandy Station battle is fought with other CSA units, not your own. You will be outnumbered, but the Union forces are not as aggressive as they could be, and your units despite their small sizes can rack up kills at high rates, thus routing attackers pretty easily.
You want to bring your units in to the fortified area, and dismount your cav. Your five artillery units also should be centrally positioned, aimed most N and S, and kept in a “hold” position so they don’t constantly swing around aiming at different targets (and exhausting themselves). Your three-star infantry units are the most powerful and should be positioned to support the main routes of attack, usually N and S. The Federals will at least try to approach you from E and W.
Mostly this mission runs on autopilot: Union units move in, are killed at high rates, rout, and retreat—rinse and repeat. But you really are short on units and the AI will try to set you up for being flanked, so you’ll need to do some micro to ensure that key units are pointing the right way when attacks come in. Once you get the hang of it you can run the timer down on fast speed.
J & P Rebalance Mod (1.27.4.3) BG
This battle may be bugged with this mod, because when I tried it, just one small skirmisher unit attacked, was repulsed, retreated out of artillery range, and never attacked again. It may be that at this point in the campaign with the mod, if you’re a decent player, USA has so few men in these battles that it declines to attack and its forces don’t even come into view.
♠♠♠
