Asopius (d.428 BC) was the son of the successful Athenian commander Phormio, but had a much less successful military career himself, being killed during his first known command (Great Peloponnesian War). In the spring of 428 BC Phormio returned to Athens from Naupactus in the Gulf of Corinth, and after this isn't mentioned again by Thucydides. The general assumption is that he died soon after returning to Athens. This is supported by a request from the Acarnanians, Athenian allies in the north-west of Greece, to have a son or relative of Phormio as the next Athenian commander in their area.
The Athenians sent Phormio's son Asopius, with a fleet of 30 ships. Asopius sailed around the Peloponnese, carrying out a series of raids on the coast of Laconia (the area around Sparta), before reaching the Athenian naval base of Naupactus, at the western end of the Gulf of Corinth. By this time he had sent eighteen of his ships back to Athens, arriving at Naupactus with the remaining twelve. In Phormio's last campaign he had led an army through Acarnania, but had decided not to attack the town of Oeniadae, the only consistently anti-Athenian town in Acarnania. Asopius decided that Oeniadea, at the south-eastern corner of Acarnania, would be his first target. His fleet sailed up the River Achelous, which formed the boundary between Aetolia and Acarnania, while the army ravaged the local area, but the citizens of Oeniadea refused to surrender.
Faced with this setback Asopius decided to abandon the campaign in Acarnania. The army was dismissed, and he led his small fleet to Leucas. This island, off the north-western tip of Acarnania, was an ally of Sparta. The town of Leucas was located at the northern end of the island, but Asopis decided to land at Nericus, at the southern end of the island. He then led his small army somewhere unspecified (possibly from his landing site to Nericus or on the fifteen mile march north to the town of Leucas), before deciding to return to his ships. Thucydides states that he was attacked 'on his way' back, but not from where. Asopius's small army was attacked by a force made up of the local people of the area, supported by a small number of troops from a garrison (probably of Nericus). Asopius and a large number of his men were killed in the resulting battle. The surviving Athenians arranged an armistice to collect their dead, and then sailed away.