Just wondering if higher campaign difficulty changes the agressiveness of the AI factions, and their ability to expand.

It seems AI factions expand at a very, very slow pace when fighting each other. The only cities the AI captures quickly are rebel ones (e.g Pontus sweeping Asia minor in a few turns). I have observed Greek Cities (AI controlled) siege Corinth (Macedon AI) 5 times (!) before finally taking it.

The reason I care is that in my campaigns (hard/hard or med/med), most of the challenge is in the early game. Once I get to 245BC or so, I am (by far) the strongest faction. Mostly because the others are still at their starting positions +/- a couple of provinces.