This reminded me of a battle between Puritans and I think Catholics in New England, sometime around one of the changes in Kings of England in the 17th century. I think.
I can't remember enough details to find the wiki article, but if you can find it it may provide some sort of inspiration for your game.
I can't remember enough details to find the wiki article, but if you can find it it may provide some sort of inspiration for your game.