@CountMRVHS : I don't think the AI in RTW has to worry about diplomatic reputation, and will exploit opportunities as they arise in a way that would not make sense for the player. I suspect that if RK had had military access in your territories it would not have attacked your settlements, but as it had landed troops in your territory, and encountered lightly defended settlements the AI figures "in for a penny, in for a pound" and goes for it. I would try reloading to before they break the peace and use money or forced diplomacy to give them military access and see if they still try to attack your settlements.
Would you do me the favor of reading @06 in the guide and comparing that to my response to your question about trading settlements above and give some suggestions on how that section could be improved to be more clear, or what is missing. Thank you for your continued help with the guide.