We often look for parallels between the state of our civilization and the fall of the Roman Empire. More important than that, I have argued, are lessons from the fall of the Roman Republic, when a centuries-old constitutional order of law and liberty was thrown away for the ideal of a divinized state and an all-powerful ruler. Also important to contemplate is the fall of the civilization of ancient Greece.
That was essentially what happened with the Peloponnesian War. The Athenian democracy and the Spartan oligarchy were both at their heights, having each established mini-empires of their own, with virtually every other city state in thrall to or an ally of one or the other. They started a war, for no good reason, which lasted nearly 30 years (from 431-404 B.C.). By the time it was over, with Sparta’s victory, Greece had squandered its ideals, thrown out its most treasured traditions, and exhausted its power. It became easy pickings for Macedonian conquest shortly thereafter.