Battle of Chalcis

Battle of Rhium
Part of the Peloponnesian War
Date 429 BC Location The mouth of the Corinthian Gulf, near present-day Rio, Greece Result Athenian victory
Belligerents
Athens	Sparta, Corinth, and other members of the Peloponnesian League
Commanders and leaders
Phormio	Machaon, Isocrates, Agatharchidas, and others
Strength
20 triremes	47 triremes, some being used as transports
Casualties and losses
None	12 ships captured, with most of their crews

The Battle of Rhium (429 BC) or the battle of Chalcis was a naval battle in the Peloponnesian War between an Athenian fleet commanded by Phormio and a Peloponnesian fleet composed of contingents from various states, each with its own commander. The battle came about when the Peloponnesian fleet, numbering 47 triremes, attempted to cross over to the northern shore of the Gulf of Patras to attack Acarnania in support of an offensive in northwestern Greece; Phormio's fleet attacked the Peloponnesians while they were making the crossing.

In the battle, the Peloponnesian ships, hampered by the fact that many of them were equipped not as fighting vessels but as transports, circled together in a defensive posture. Phormio, taking advantage of his crews' superior seamanship, sailed around the clustered Peloponnesians with his ships, driving the Peloponnesians closer and closer together until they began to foul oars and collide with each other. The Athenians then suddenly attacked, routing the Peloponnesians and capturing 12 ships.

The summer of 429 BC was marked by a Peloponnesian offensive in the Greek northwest. The Spartans and their allies hoped to knock several Athenian allies such as Acarnania, Zacynthus, and Cephallenia out of the war, and if possible to capture the Athenian base at Naupactus. The Spartan (navarch) Cnemus was placed in command of the campaign. He set out against Acarnania with 1,000 hoplites from Sparta, crossing over the Corinthian Gulf unnoticed by Phormio. Combining his forces with 2,000 troops sent from allied states, Cnemus moved against the city of Stratus, an Acarnanian ally. The Acarnanians appealed to Phormio for help, but he refused to leave Naupactus undefended.

The Peloponnesian fleet, meanwhile, was charged with ferrying troops to the southern coast of Acarnania to prevent the residents of that area from supporting their allies inland. As the Peloponnesians moved westward along the south coast of the Gulf of Corinth, the Athenian fleet followed them on the northern shore. The Peloponnesians, with 47 ships, were not particularly concerned about the 20 Athenians ships across the gulf, but they nonetheless left their moorings at night to pass through the strait between Rhium and Cape Antirrhium, hoping to give their pursuers the slip. This ruse failed, as the Athenians noticed the move and gave chase, catching the Peloponnesians in the open water of the Gulf of Patras.

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