Cunning Realist writes on trauma cocktails which effectively make a nation accept anything; breaking down individual and social norms such that extremes become accepted as the new norm.
One of the interesting aspects of the Peloponnesian War was that the normal method of determining conflict between Greek city-states, hoplite battle, was replaced with political and ethnic genocide. Asymmetric warfare ruined the wealth, morality and power of Greece such that the Macedonians and then the Romans replaced them as the centre of Mediterranean power.
The shocks of two generations of continuous warfare, asymmetry, ethnic genocide, political turbulence, political genocide (people were wiped out for being oligarchic or democratic in their politics), plus the plague in Athens all led to a Greek trauma cocktail where plunder and genocide became the norm. It destroyed the power of Athens and Sparta; making them easy prey for Phillip of Macedonia and later the foreign policy politics of Rome's Scipio Africanus.