History of the Peloponnesian War

The origin of our quarrel was this. We settled Plataea some time after the rest of Boeotia, together with other places out of which we had driven the mixed population. The Plataeans not choosing to recognize our supremacy, as had been first arranged, but separating themselves from the rest of the Boeotians, and proving traitors to their nationality, we used compulsion; upon which they went over to the Athenians, and with them did us much harm, for which we retaliated.