History of the Peloponnesian War

But he, induced by the Messenians whom he favoured, but especially because he thought without the forces of the people of Athens with the confederates only of the continent and with the Aetolians to invade Boeotia by land, going first through the Locri Ozolae and so to Cytinium of Doris, having Parnassus on the right hand till the descent thereof into the territory of the Phoceans, which people, for the friendship they ever bore to the Athenians, would, he thought, be willing to follow his army, and if not, might be forced; and upon the Phoceans bordereth Boeotia; putting off therefore with his whole army, against the minds of the Acarnanians, from Leucas, he sailed unto Solium by the shore.

And there, having communicated his conceit with the Acarnanians, when they would not approve of it because of his refusal to besiege Leucas, he himself with the rest of his army, Cephalonians, Zacynthians, and three hundred Athenians, the soldiers of his own fleet (for the fifteen galleys of Corcyra were now gone away), warred on the Aetolians, having Oeneon, a city of Locris, for the seat of his war.

Now these Locrians called Ozolae were confederates of the Athenians and were to meet them with their whole power in the heart of the country. For being confiners on the Aetolians and using the same manner of arming, it was thought it would be a matter of great utility in the war to have them in their army for that they knew their manner of fight and were acquainted with the country.