I tried blocking the bridge with a treb in a bridge battle with the Mongols yesterday. Oddly the Mongols became smart and just waited at the other end, not too smart though, I used my other trebs to blast them into kingdom come
Its only after the barrage where the problem comes. They still overpower my forces so its either I try to lure them in or withdraw. But in the cases they decide to cross the bridge, I win hands down and my losses are only less than a 100.
Bookmarks