History of the Peloponnesian War

This they negotiated with one Eurymachus the son of Leontiadas, one of the most potent men of Thebes. For the Thebans, foreseeing the war, desired to preoccupy Plataea, which was always at variance with them, whilst there was yet peace and the war not openly on foot. By which means they more easily entered undiscovered, there being no order taken before for a watch.