You're forgetting they have one of Tilly's witches that can mold dirt and mud into solid walls capable of forming two story houses as you saw in past images of the Fjord stronghold. So it's no problem for creating eight cannon-emplacement bunkers on each side of the river for a total of 16 hidden bunkers. Each bunker is basically a pillbox with a small opening for the cannon. I was expecting those careless overconfident dorks to parade around the opening again and have a spear or arrow poke them as in that long ago chapter.is a bunker made out on nothing but loose dirt a good idea?