Glenn, what difficulty are you playing on? What I have gathered from these forums, it seems that with medium campaign difficulty AI does not act like the rabid dog it is in very hard campaigns. Also, playing as Casse has the advantage of not having a land border with any AI factions, a situation which has the tendency to make AI's binaric eyes glee with maniacal battlelust.

In accordance to how to machinate AI attack, I can only speculate. When things work out it, it might be that AI isn't in a war with anyone and has enough troops and when the declaration of war was made it chose to attack it's new enemies. If things don't work out, it might be that AI didn't have enough troops to attack, or it had another goal in mind and couldn't change it (AI cannot handle 2 fronts at a time).

RTW diplomacy engine is quite limited in options, has been butchered by the systems unmoddability and AI's warlust against human player and suffers from the not-so-bright AI. Still, when stars are aligned correctly and everything works right it can stretch to good deeds, what is clearly shown in Glenn's post.