The battle of Chios (357 or 356 BC) was the first fighting during the Social War, and saw the rebels defeat an Athenian land and sea attack on the island.
The Social War was triggered by the refusal of Chios to pay its annual contribution to the Athenian League. Chios, Rhodes and Byzantium were at the heart of the revolt, joined by Cos, and supported by Mausolus, satrap of Caria. The rebels concentrated their forces at Chios, a sizable island off the west coast of Asia Minor, and the nearest of the rebel states to Athens.
The Athenians also decided to deal with Chios first. Chares and Chabrias were give command of the army and fleet that was sent to deal with the revolt (Cornelius Nepos provides a different version, in which Chabrias was present in a private capacity, but ended up with more influence than the real commanders). They arrived at Chios after the allies, and decided to attack. The army, under Chares, was landed on the island, while Chabrias commanded the fleet. Diodorus hints at a siege followed by a unsuccessful assault on the city, although it is possible that the assault was made immediately after the Athenians arrived.
The plan was for a two pronged assault. Chabrias was to lead the fleet into the harbour, where he would attack the Allied fleet. Chares would attack from the land.
Chabrias was soon caught up in a fierce naval battle. His ship was rammed, and probably immobilised. He may have got ahead of the rest of the fleet, as the other ships withdrew intact. According to Diodorus Chabrias chose to fight on, and died of his wounds. Cornelius Nepos has Chabrias dashing ahead of the rest of the fleet as he wanted to be the first into the harbour. He was then surrounded, and chose to fight to the death rather than swim to safety.
As Chares advanced towards the wall, the defenders sortied from the city and a battle took place outside the walls. Diodorus gives no further details of this battle,