If you get a papal warning, then you must assault the forts you are besieging the turn after you get the warning. If you besiege for another year, then assault, you will be excommunicated. Also, you cannot invade the turn after you get a warning, then assault the turn after that or you will be excommunicated. So basically once you recieve the warning, no new offensives other than immediately assaulting castles. If you dont mind getting excommunicated, then go ahead and just ignore it.
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