The battle of the Arginusae Islands (406 BC) was the last major Athenian victory of the Great Peloponnesian War, but after the battle six of the eight victorious generals were executed for failing to rescue the crews of the twenty five Athenian warships lost during the battle.
At the start of the campaigning season in 406 BC the Athenians had a fleet of 70 ships in Asia Minor, commanded by Conon, while the Peloponnesians had 140 ships under the newly appointed Callicratidas. He achieved a series of early successes, capturing Delphinium in the territory of Chios and Methymne on Lesbos. He then chased Conon into Mytilene, sinking or capturing thirty of the seventy Athenian ships, and began a siege of Mytilene.
When this news reached Athens a new fleet was scraped together. Our two main sources agreed on the eventual size of the Athenian fleet, but not on its composition. According to Xenophon 110 ships came from Athens, ten were at Samos and thirty were provided by other allies, for a total of 150. In Diodorus Siculus sixty ships came from Athens, ten from Samos and eighty from other Athenian allies, again for a total of 150. The fleet came together at Samos, and sailed up the coast towards Lesbos, pausing on the night before the battle at the Arginusae Islands, east of Lesbos and close to the mainland.
Callicratidas decided to intercept the Athenian fleet, a sign of the greatly increased confidence of the Peloponnesian fleet. He left fifty ships at Mytilene, and took one hundred and twenty with him.
The Athenian fleet was drawn up in two lines. At the far left was Aristocrates with fifteen ships, and with Pericles (son of the famous statesman) behind him. Next was Diomedon with fifteen ships and Erasinides behind. In the centre were the ten Samian ships, ten ships commanded by the Athenian taxiarchs, three by the navarchs and other allies. Next was Protomachus with Lysias behind him, both with fifteen ships. Finally on the far right Thrasylus commanded the front line and Aristogenes the rear. The Athenian left wing pointed out to open sea, the right towards the shore and the Arginusae islands were in the centre of the line. The Athenians hoped that this formation would prevent the Spartans from breaking their line, while the islands extended their line and would make it harder for the Spartans to outflank it.
Callicratidas was effectively forced to split his fleet in two. He commanded on the right, while the Boeotians, commanded by Thrasondas of Thebes, held the left.
Neither Xenophon or Diodorus give us any real details of the battle, other than to agree that it was hard fought and lasted for some time. Callicratidas was killed during the battle, although our sources disagree on how. According to Xenophon he fell overboard after his ship rammed an Athenian ship, and was drowned. In Diodorus he was killed fighting onboard his ship, after becoming entangled with Pericles' ships. Our sources also disagree on which wing of the Peloponnesian fleet was defeated first - the right wing goes first in Diodorus and the left wing in Xenophon. In both sources most of the Peloponnesians fled south to Chios.
Our sources give largely similar casualty figures, with the Peloponnesians loosing 70-77 ships and the Athenians twenty ships along with most of their crews. This loss of crew would lead to the most controversial aspect of the battle. The Athenian commanders apparently decided to split their fleet, sending some ships to lift the siege of Mytilene and some to rescue their shipwrecked comrades, but a storm blew up, and the fleet was forced to return to shore without achieving either objective.
This gave Eteonicus, the Peloponnesian commander at Mytilene, time to evacuate his army and fleet. Conon was able to emerge from the blockaded city, and joined up with the main Athenian fleet. Meanwhile news of the battled reached Athens, where the initial celebrations of victory were marred by the news of the heavy losses. The generals were blamed for failing to rescue the shipwrecked men, and were dismissed. Conon, Adeimantus and Philocles were appointed to replace them. Of the eight generals in command during the battle Protomachus and Aristogenes decided not to return to Athens. Pericles, Diomedon, Lysias, Aristocrates, Thrasylus and Erasinides returned to the city, where they were put on trial and after a somewhat lengthy process condemned and executed.
The Athenian people soon regretted their decision, but it was too late. The execution of six victorious generals had a double effective - it removed most of the most able and experienced commanders, and it discouraged the survivors from taking command in the following year. This lack of experience may have played a part in the crushing Athenian defeat at Aegospotami that effectively ended the war.