History of the Peloponnesian War

When they were all together, they sat down about break of day at a place called Metropolis and there encamped. And the Athenians not long after with their twenty galleys arrived in the Ambracian gulf to the aid of the Argives, to whom also came Demosthenes with two hundred Messenian men of arms and threescore Athenian archers.

The galleys lay at sea before the hill upon which the fort of Olpae standeth. But the Acarnanians, and those few Amphilochians (for the greatest part of them the Ambraciotes kept back by force) that were come already together at Argos, prepared themselves to give the enemy battle, and chose Demosthenes, with their own commanders, for general of the whole league. He, when he had brought them up near unto Olpae, there encamped.

There was between them a great hollow. And for five days together they stirred not; but the sixth day both sides put themselves into array for the battle. The army of the Peloponnesians reached a great way beyond the other, for indeed it was much greater; but Demosthenes, fearing to be encompassed, placed an ambush in a certain hollow way and fit for such a purpose, of armed and unarmed soldiers, in all to the number of four hundred; which, in that part where the number of the enemies overreached, should in the heat of the battle rise out of ambush and charge them on their backs.