I don't know if this is a bug or just an AI fault or something to do with power level calculation, but the Resoln declared war on me and two turns later had their sovereign's army parked outside my border town.

"Great," I thought, "They've planned this war out, then!"

They then proceeded to attack a fortress with 14 defender groups with an army of 5 units, in a battle they couldn't possibly hope to win, and proceeded to get slaughtered without killing anything. It was very strange, and I'm not sure if the AI is meant to be this suicidal. I was playing on Hard difficulty. Has anyone else encountered something like this?