In my Mac campaign, I'm around 243 BC, firmly establishing my presence in Anatolia. I have Pergamon, Halicarnasos, Sardis and Nicea. AS are fighting the Ptolies, losing Antiochia to them and Damascus (but retake Damascus later).They are also fighting Pahlava and losing their north-eastern and some central provinces. Overall their position is not good.

I'm their ally from the start and since I see that they are in a though position, I decide to help them. I attack the Ptolies and take Salamis, then I take one of their towns on the southern coast of Asia Minor. Previously (7-10 years earlier) I've killed off KH (that's how I took Sardis) who were also fighting the AS in Anatolia and were the Ptolies' allies. One turn ago Baktria declared war on AS too and what I see the very next turn: AS, who were trying to sneak their spy for some time already into Pergamon and failed, move in their assassin and kill my governor there. At that time I have my king's army in Southern Anatolia and another army, consisting only of professional and elite troops in Nikea. The only thing the AS get from that assassination is that the public order in Pergamon dropped to 80%. But, I already signed a truce with the Ptolies and my armies are ready to wipe out AS in Anatoia in a war that will be started in the next couple of turns.

What is the reasoning behind AI actions? I know, the AI sometimes does strange things, but here it's like signing a death verdict to their own empire.