Quote Originally Posted by CrossLOPER
In STW, allies become war hungery and seem attack everyone they can once they have secured a border. Behavior more or less depends on what situation your ally is in.
In S:TW, it depended mainly on the A.I. personality. The Takeda clan would break alliances for no reason other than that their leaders was bored. On the other hand, Hojo tended to be very reliable. This mechanism was present in M:TW as well, but I got the impression that A.I. personalties changed far more rapidly.