History of the Peloponnesian War

After this, when he saw his opportunity, he brought out the army again. Nicias and the Athenians, who thought it necessary, if not to begin the battle, yet by no means to set light by the wall in hand (for by this time it wanted but little of passing the point of theirs, and proceeding, would give the enemy advantage, both to win if he fought, and not to fight unless he listed), did therefore also set forth to meet the Syracusians.

Gylippus, when he had drawn his men of arms farther without the walls than he had done before, gave the onset. His horsemen and darters he placed upon the flank of the Athenians, in ground enough, to which neither of their walls extended.

And these horsemen, after the fight was begun, charging upon the left wing of the Athenians next them, put them to flight; by which means the rest of the army was by the Syracusians overcome likewise and driven headlong within their fortifications.

The night following, the Syracusians brought up their wall beyond the wall of the Athenians so as they could no longer hinder them, but should be utterly unable, though masters of the field, to enclose the city.