Demosthenes formed the right wing of the Athenian-led army with Athenian and Messenian troops, with the centre and left wing formed by the Acarnanians and Amphilochians. Eurylochus formed the left wing of his army, directly facing Demosthenes, with the Ambraciots and Mantineans forming the rest of the line. When the battle began, Eurylochus quickly outflanked Demosthenes and was about to surround him when the Acarnanians began their ambush, causing panic among the other troops when Eurylochus was killed. The Ambraciots defeated the left wing of the Acarnanians and Amphilochians, chasing them back to Argos, but they were themselves defeated by the rest of the Acarnanians when they returned. Demosthenes lost about 300 men, but emerged victorious when the battle was completed later that night.

The next day, Menedaius, who had taken command when Eurylochus was killed, attempted to arrange a truce with Demosthenes. Demosthenes would only allow the leaders of the army to escape. However, some of the Ambraciots attempted to flee with Menedaius and the other commanders. The Acarnanians chased them, allowed Menedaius to escape as agreed, and killed about 200 Ambraciots.

Meanwhile, Demosthenes learned that a second army from Ambracia was marching towards Olpae. These Ambraciots set up camp on the road to the fort, having no knowledge of the defeat of the previous day. Demosthenes surprised them there at night, pretending to be the other Ambraciot army, and killed most of them; the rest fled to the hills or into the sea where they were captured by the 20 Athenian ships. Overall, the Ambraciots lost about 1000 men over the two days.

Although Demosthenes could have easily taken Ambracia, he did not, and the Acarnanians and Ambraciots signed a 100-year peace treaty with them.

Robert B. Strassler ed., The Landmark Thucydides: a Comprehensive Guide to the Peloponnesian War- (The Free Press, 1996) ISBN 0-684-82815-4