Lol wait, now a full fledged war? XD
Actually I thought of an interesting idea of that. While it depends on the region the person is from, or perhaps their style of attack etc.
A brigade could be similar to that of a Pokemon deck (from the TCG) where there will be a majority of one or two types of Pokemon, this way it will also make describing the moves slighlty easier.
But you'd also have to look at it realistically... Perhaps it is easier for the opponents to breed easy-to-breed pokemon... Like lets say it is easier to make a ton of Taurases...
It would definitely suck to describe or say otherwise that there were 300 different kinds of pokemon in the battle...
Or you could also describe a part of the battle, like how the reader is reading about how specific pokemon are fighting or that particular attacks are just so overwhelming.
Perhaps an intersting way to describe it, would be to think of yourself as a camera, now take that camera and start flying with it before, during and after the battle area.
"Pokemon clashed... A Nidoran was seen upturning an Ivysaur with its horn... Blood was being shed everywhere." etc (half baked example mind you...)
You also want to make the war look tough for both sides... Unless of course your pokemon are like the spartans.
You want the reader to feel for the protagonist's side. And the thing is, you don't have to be blatant about it... like the bad guys all wearing black armour and giving menacing looks. What can make it more fearful is that (if especially they have the upperhand) they are presented as merely human and pokemon, nothing more.
Perhaps a good example of this is Cyrus, he gives off a good vibe at first... but then suddenly his plan is in full spin, of course we can do better than that though, because the show was meant for kids, and dialogue limits to some extent.