History of the Peloponnesian War

We quarrelled then with them in the first instance, because, on our settling Plataea at a later period than the rest of Boeotia, and some other places with it, of which we took possession after driving out their mixed population, these men did not think fit, as had been first arranged, to submit to our supremacy, but, apart from the rest of the Boeotians, offended against the principles of their fathers, and when they were being compelled to observe them, went over to the Athenians, in conjunction with whom they did us many injuries, for which they also suffered in return.