History of the Peloponnesian War

Afterwards, when Brasidas had dismissed the allies to their several cities, he himself went back to Corinth, and prepared for his expedition to Thrace, which was his original destination.

When the Athenians also had returned home, such of the Megareans in the city as had been most implicated in the negotiations with them, knowing that they had been marked, immediately stole away; while the rest, having conferred with the friends of the exiles, restored the party at Pegae, after binding them by solemn oaths to forget the past, and to advise what was best for the city.

When, however, they had been put in office, and held a review of the heavy-armed troops, having separated the battalions, they selected a hundred of their enemies, and of those who appeared to have joined most decidedly in the negotiations with the Athenians; and having compelled the commons to pass an open sentence upon them, on their being condemned, they put them to death, and established a thorough oligarchy in the city.

And this change of government lasted a very long time, though effected by a very few men through the triumph of a faction.