Originally Posted by GeneralMikeIII
IIRC, in M1TW, the later castles could be upgraded to include seige towers containing ballista, catapults, and in the late game even cannons. You didn't have to have seige weapons stationed in the province (in fact, if you did, they usually just put them inside the walls of the castle, but not on them. This was kinda nice though, because the high Angle of Fire of the catapults allowed you to lob rocks over the wall onto the besiegers as they approached and not have to worry about taking return fire, at least until the walls were breached). I assume it will be the same in M2, since I haven't heard anything to the contrary.