While the enemy was taking up his dead and hastily burying them as he could, and those who obtained permission were secretly planning their retreat, word was brought to Demosthenes and the Acarnanians that the Ambraciots from the city, in compliance with the first message from Olpae, were on the march with their whole levy through Amphilochia to join their countrymen at Olpae, knowing nothing of what had occurred. Demosthenes prepared to march with his army against them, and meanwhile sent on at once a strong division to beset the roads and occupy the strong positions. In the meantime the Mantineans and others included in the agreement went out under the pretence of gathering herbs and firewood, and stole off by twos and threes, picking on the way the things which they professed to have come out for, until they had gone some distance from Olpae, when they quickened their pace. The Ambraciots and such of the rest as had accompanied them in larger parties, seeing them going on, pushed on in their turn, and began running in order to catch them up. The Acarnanians at first thought that all alike were departing without permission, and began to pursue the Peloponnesians; and believing that they were being betrayed, even threw a dart or two at some of their generals who tried to stop them and told them that leave had been given. Eventually, however, they let pass the Mantineans and Peloponnesians, and slew only the Ambraciots, there being much dispute and difficulty in distinguishing whether a man was an Ambraciot or a Peloponnesian. The number thus slain was about two hundred; the rest escaped into the bordering territory of Agraea, and found refuge with Salynthius, the friendly king of the Agraeans.
Meanwhile the Ambraciots from the city arrived at Idomene. Idomene consists of two lofty hills, the higher of which the troops sent on by Demosthenes succeeded in occupying after nightfall, unobserved by the Ambraciots, who had meanwhile ascended the smaller and bivouacked under it. After supper Demosthenes set out with the rest of the army, as soon as it was evening; himself with half his force ****** for the pass, and the remainder going by the Amphilochian hills. At dawn he fell upon the Ambraciots while they were still abed, ignorant of what had passed, and fully thinking that it was their own countrymen- Demosthenes having purposely put the Messenians in front with orders to address them in the Doric dialect, and thus to inspire confidence in the sentinels, who would not be able to see them as it was still night. In this way he routed their army as soon as he attacked it, slaying most of them where they were, the rest breaking away in flight over the hills. The roads, however, were already occupied, and while the Amphilochians knew their own country, the Ambraciots were ignorant of it and could not tell which way to turn, and had also heavy armour as against a light-armed enemy, and so fell into ravines and into the ambushes which had been set for them, and perished there. In their manifold efforts to escape some even turned to the sea, which was not far off, and seeing the Athenian ships coasting alongshore just while the action was going on, swam off to them, thinking it better in the panic they were in, to perish, if perish they must, by the hands of the Athenians, than by those of the barbarous and detested Amphilochians. Of the large Ambraciot force destroyed in this manner, a few only reached the city in safety; while the Acarnanians, after stripping the dead and setting up a trophy, returned to Argos.