Well, if you push them slowly... (capture their city, reinforce it, but let them grow to opposite site... For example, when attacked from the south, in my now running KH campaign, they'll found themself ways to kick Gallic (Aedui's and Avernii's) ass, and then made them as a partially culturalized barbaroi of the north. But when pressed from the north, that goes in my Sweboz camp, they'll just go nuts, and conquer Karthadast... not sure what'll they do when attacked from both side, but at least I can tell, Caralis and Sardinia are their favourite last vacation resorts anyway... (in BI), in Alex, they just try to fight back more fierely on you......