Guide: Bandar Log - you whipped me with what?!?

[Loren]

Originally Posted by Rytek

Ah yes, the AI. A quick tip to avoid that: If 2 AI's are at war with each other. And one is at war with you and the other is not you must make sure that the AI you are at peace with cannot come adjacent to you sieging the AI that you are both at war with. The AI that has peace with you does not recognize you as owning the sieged castle yet. So, it will attack your force laying siege to the castle. If that happends, win or lose, the AI that you had peace with will consider itself at war with you. To prevent that, you must prevent that peacfull AI from getting adjacent to the castle you wish to siege. If you must, take that sieging army attack all around the castle, cutting the friendly AI off from getting to the castle. Even if both you and the friendly AI hit the same enemy ai province war will not be declared as long as it did not happen in a fort province.

As far as I can tell such a battle happening as part of a siege doesn't trigger war. It looks like war depends on who owned the province at the start of the turn.

What happened in this case was it was a suicidal attack by his pretender. Kill a pretender and it's war no matter what.