In 415 BC, the Athenian assembly led by Alcibiades, voted to invade Sicily. The city-state of Segesta had promised huge financial aid in return for assistance against its enemy Selinus. With a foothold in Sicily the Athenians would also gain a tactically advantageous position from which to attack Sparta, if war broke out between the two great powers once more.

Setting off with a fleet of 100 triremes, numerous transport and cargo ships, over 5000 hoplites and additional archers and slingers, the armada was confident of an easy victory. Yet before it was more than a few days out to sea it received its first setback. Alcibiades was recalled to answer charges of religious sacrilege. Jumping ship he sought the protection of Sparta and the war began again in earnest.

Meanwhile the Athenian invasion of Sicily did not proceed well. The Segestans had tricked them about the extent of their wealth and military strength, and in 413 Athens was forced to send out another 60 ships as reinforcements.

Trapped behind their city walls, the Athenians heard no news for three months. Then, according to Plutarch (Rise & Fall of Athens, 7:30) a sailor arrived at the Piraeus in need of a haircut. He told the barber an appalling story of an invasion force decimated in a failed invasion of Sicily. Athens had suffered the most spectacular defeat in its history.