To this plan Demosthenes consented, not only to please the Messenians, but also in the belief that by adding the Aetolians to his other continental allies he would be able, without aid from home, to march against the Boeotians by way of Ozolian Locris to Kytinium in Doris, keeping Parnassus on his right until he descended to the Phocians, whom he could force to join him if their ancient friendship for Athens did not, as he anticipated, at once decide them to do so. Arrived in Phocis he was already upon the frontier of Boeotia. He accordingly weighed from Leucas, against the wish of the Acarnanians, and with his whole armament sailed along the coast to Sollium, where he communicated to them his intention; and upon their refusing to agree to it on account of the non-investment of Leucas, himself with the rest of the forces, the Cephallenians, the Messenians, and Zacynthians, and three hundred Athenian marines from his own ships (the fifteen Corcyraean vessels having departed), started on his expedition against the Aetolians. 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. Led on by his advisers and trusting in his fortune, as he had met with no opposition, without waiting for his Locrian reinforcements, who were to have supplied him with the light-armed darters in which he was most deficient, he advanced and stormed Aegitium, the inhabitants flying before him and posting themselves upon the hills above the town, which stood on high ground about nine miles from the sea. Meanwhile the Aetolians had gathered to the rescue, and now attacked the Athenians and their allies, running down from the hills on every side and darting their javelins, falling back when the Athenian army advanced, and coming on as it retired; and for a long while the battle was of this character, alternate advance and retreat, in both which operations the Athenians had the worst.
Still as long as their archers had arrows left and were able to use them, they held out, the light-armed Aetolians retiring before the arrows; but after the captain of the archers had been killed and his men scattered, the soldiers, wearied out with the constant repetition of the same exertions and hard pressed by the Aetolians with their javelins, at last turned and fled, and falling into pathless gullies and places that they were unacquainted with, thus perished, the Messenian Chromon, their guide, having also unfortunately been killed. A great many were overtaken in the pursuit by the swift-footed and light-armed Aetolians, and fell beneath their javelins; the greater number however missed their road and rushed into the wood, which had no ways out, and which was soon fired and burnt round them by the enemy. Indeed the Athenian army fell victims to death in every form, and suffered all the vicissitudes of flight; the survivors escaped with difficulty to the sea and Oeneon in Locris, whence they had set out. Many of the allies were killed, and about one hundred and twenty Athenian heavy infantry, not a man less, and all in the prime of life. These were by far the best men in the city of Athens that fell during this war. Among the slain was also Procles, the colleague of Demosthenes. Meanwhile the Athenians took up their dead under truce from the Aetolians, and retired to Naupactus, and from thence went in their ships to Athens;Demosthenes staying behind in Naupactus and in the neighbourhood, being afraid to face the Athenians after the disaster.
About the same time the Athenians on the coast of Sicily sailed to Locris, and in a descent which they made from the ships defeated the Locrians who came against them, and took a fort upon the river Halex.
The same summer the Aetolians, who before the Athenian expedition had sent an embassy to Corinth and Lacedaemon, composed of Tolophus, an Ophionian, Boriades, an Eurytanian, and Tisander, an Apodotian, obtained that an army should be sent them against Naupactus, which had invited the Athenian invasion. The Lacedaemonians accordingly sent off towards autumn three thousand heavy infantry of the allies, five hundred of whom were from Heraclea, the newly founded city in Trachis, under the command of Eurylochus, a Spartan, accompanied by Macarius and Menedaius, also Spartans.