Enemy Civil War: Given the Empire’s preference for deviousness and indirection, not to mention preemption, by way of military policy, this happens surprisingly often.  Well, okay, still not all that often, but if a society has a crack in it that a skillful warrior-philosopher/memeticist can use to get them fighting each other rather than running around fighting other people, the Stratarchy of Indirection and Subtlety considers that a net win.