History of the Peloponnesian War

Thucydides

Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.

When the winter was now ending the Boeotians took Oropus, where the Athenians had a garrison, by treachery. And they had the cooperation of some men of Eretria and of Oropus itself who were plotting for the revolt of Euboea. For since the place is opposite Eretria, it was impossible, while the Athenians held it, that it should not injure greatly both Eretria and Euboea in general.