History of the Peloponnesian War

When the winter was now closing, the Boeotians took Oropus by treachery, while an Athenian garrison was holding it. There co-operated with them, also, some of the Eretrians and of the Oropians themselves, who were plotting the revolt of Euboea. For as the place was just opposite to Eretria, so long as the Athenians held it, it could not fail to do much damage both to Eretria and the rest of Euboea.