The war waged between Athens and Sparta and their respective allies between 431 and 404 bc. Sparta invaded Attica with its allies in 431, but Pericles had persuaded the Athenians to withdraw behind the ‘long walls’, which linked Athens and its port of Piraeus, and avoid a land-battle with Sparta’s superior army. Athens relied on its fleet of triremes to raid the Peloponnese and guard its empire and trade-routes. It was struck a serious blow by an outbreak of plague in 430, which killed about a third of the population, including Pericles. Nevertheless the fleet performed well and a year’s truce was made in 423 bc.

The Peace of Nicias was concluded in 421 bc, but Alcibiades orchestrated opposition to Sparta in the Peloponnese, though his hopes were dashed when Sparta won a victory at Mantinea in 418. He was also the main advocate of an expedition to Sicily (415–413), aimed at defeating Syracuse, that ended in complete disaster for Athens. War was formally resumed in 413 bc. Athenian fortunes revived, with naval victories at Cynossema (411), Cyzicus (410), and the recapture of Byzantium (408). There was a further victory at Arginusae in 406. From then on, Persian financial support for Sparta and the strategic and tactical skills of the Spartan Lysander tilted the balance. Sparta’s victory at Aegospotami and its control of the Hellespont starved Athens into surrender in April 404. An oligarchic coup followed immediately, supported by Sparta, and the reign of terror of the ‘Thirty Tyrants’, but democracy was restored in 403.