History of the Peloponnesian War

The same winter the Ambraciotes, according to their promise made to Eurylochus when they retained his army, made war upon Argos in Amphilochia with three thousand men of arms, and invading Argeia, they took Olpae, a strong fort on a hill by the sea-side, which the Acarnanians had fortified and used for the place of their common meetings for matters of justice, and is distant from the city of Argos, which stands also on the sea-side, about twenty-five furlongs.

The Acarnanians, with part of their forces, came to relieve Argos; and with the rest they encamped in that part of Amphilochia which is called Crenae to watch the Peloponnesians that were with Eurylochus that they might not pass through to the Ambraciotes without their knowledge;