His base he established at Oeneon in Locris, as the Ozolian Locrians were allies of Athens and were to meet him with all their forces in the interior.

Being neighbours of the Aetolians and armed in the same way, it was thought that they would be of great service upon the expedition, from their acquaintance with the localities and the warfare of the inhabitants.
After bivouacking with the army in the precinct of Nemean Zeus, in which the poet Hesiod is said to have been killed by the people of the country, according to an oracle which had foretold that he should die in Nemea, Demosthenes set out at daybreak to invade Aetolia.

The first day he took Potidania, the next Krokyle, and the third Tichium, where he halted and sent back the booty to Eupalium in Locris, having determined to pursue his conquests as far as the Ophionians, and, in the event of their refusing to submit, to return to Naupactus and make them the objects of a second expedition.

Meanwhile the Aetolians had been aware of his design from the moment of its formation, and as soon as the army invaded their country came up in great force with all their tribes; even the most remote Ophionians, the Bomiensians, and Calliensians, who extend towards the Malian Gulf, being among the number.
The Messenians, however, adhered to their original advice.

Assuring Demosthenes that the Aetolians were an easy conquest, they urged him to push on as rapidly as possible, and to try to take the villages as fast as he came up to them, without waiting until the whole nation should be in arms against him.