11 events the sources record for this year, grouped by region.
What happened
Southern Europe (11)
The Syracusan generals, realizing they had been deceived, turned back and attacked the Athenian camp. (Diodorus Siculus, Library of History 13.6.5)
He enters seven chariots at the Olympic Games and takes first, second and fourth places (Plutarch's Parallel Lives Plut. Alcibiades 11)
When Egesta and Leontini envoys request an expedition, Nicias opposes it but loses (Plutarch's Parallel Lives Plut. Nicias 12)
Athens sets out against Melos with 30 of its own ships (joined by 6 from Chios and 2 from Lesbos), 1,600 hoplites, 300 archers, 20 mounted archers, and about 1,500 allied and island hoplites (Thucydides, History of the Peloponnesian War 5.84.1)
With reinforcements and internal betrayal Melos surrenders; the adult men are executed, the women and children enslaved, and 500 colonists settled (Thucydides, History of the Peloponnesian War 5.116.3–4)
Athens resolves to launch a second Sicilian expedition with a larger fleet, not knowing the size of the island or its population (Thucydides, History of the Peloponnesian War 6.1.1)