Unlike the Roman and Carthaginian superfactions that must be broken through civil war, the Greek superfactions (Sparta and Athens) are also broken whenever one of them is destroyed - meaning if Athens is destroyed, the Spartan superfaction is broken and all its members become neutral towards each other (and vice-versa). The members of the superfaction whose leader was destroyed remain allies, but are no longer affected by the usual superfaction restrictions (meaning they can break the alliance at any time).