History of the Peloponnesian War

The Athenian generals, having observed this and being desirous to draw forth the Syracusians' whole power as far as might be from the city, to be able in the meantime without impeachment, going thither in the night by sea, to seize on some convenient place to encamp in; for they knew they should not be able to do it so well in the face of an enemy prepared, nor if they were known to march by land, for that the Syracusian horsemen being many would greatly annoy the light-armed and other multitude, they themselves having no horsemen there; whereas thus they might possess themselves of a place where the horse could not do them any hurt at all to speak of (now the Syracusian outlaws that were with them had told them of a place near the temple Olympieium, which also they seized); I say, the Athenian generals, to bring this their purpose to effect contrived the matter thus:

They send a man, of whose fidelity they were well assured, and in the opinion of the Syracusian commanders no less a friend of theirs. This man was a Catanaean and said he came from Catana, from such and such, whose names they knew, and knew to be the remnant of their well-willers in that city.

He told them that the Athenians lay every night within the town and far from their arms; and that if with the whole power of their city, at a day appointed betimes in a morning they would come to their camp, those friends of the Syracusians would shut the Athenians in and set on fire their galleys, by which means the Syracusians, assaulting the pallisado, might easily win the camp, and that the Catanaeans that were to help them herein were many, and those he came from already prepared for it.