History of the Peloponnesian War

Demosthenes was induced to make this decision, not only by his desire to please the Messenians, but chiefly because he thought that, without help from Athens, he would be able with his allies from the mainland, once the Aetolians had joined him, to make an overland expedition against the Boeotians by passing through the country of the Ozolian Locrians to Cytinium in Doris, keeping Parnassus on the right, until he should descend into Phocian territory. The Phocians would presumably be eager to join the expedition in view of their traditional friendship with Athens, or else could be forced to do so; and Phocis is on the very borders of Boeotia. So he set sail from Leucas with his whole armament in spite of the unwillingness of the Acarnanians and went along the coast to Sollium.

There he made his plan known to the Acarnanians, but they would not agree to it because of his refusal to invest Leucas; he therefore set out upon his expedition against the Aetolians without them, taking the rest of his army, which consisted of Cephallenians, Messenians, Zacynthians, and three hundred Athenian marines from his own ships—for the fifteen Corcyraean ships had gone back home. The base from which he started was Oeneon in Locris.

The people of this country, Ozolian Locris, were allies, and they with their whole force were to meet the Athenians in the interior; for since they were neighbours of the Aetolians and used the same sort of arms, it was believed that their help would be of great service on the expedition on account of their knowledge both of the Aetolian manner of fighting and of the country.