Quote Originally Posted by NodachiSam
They probably do that because the AI is programmed to be really concerned about you. If they share a border they are likely to beef it up.
That may well be true, but the Byzantines regularly leave Constantinople undefended when the Turks have captured Nicea and I am playing as Egyptians.

If the Danes take Sweden they can grow big, but they seldom do. For some reason they are more likely to attack Sweden if you or another faction takes it then when it's rebel held. Aragon seems programmed to take Toulouse and occasionally attacks Valencia, but I have never seen them do both. Almohads were a monster in early M:TW but pathetic in VI.

On the other hand, the Sicilians can be very annoying. They seldom form a big empire, but I have seen them attack North Africa and Spain, and they often go at war with the Papacy and the Italians, so I wouldn't call them passive. Also their ships are a major pain if you are trying to set up a Mediterranean trade network. The Pope went berserk in several of my games, but I cannot remember if this was the consequence of a reemergence. In other games, however, he never gets beyond Genoa. However, one might argue that it's not his purpose to go conquering.