Peloponnesian War

War fought 431–404 BC between Athens and Sparta and their respective allies, involving most of the Greek world from Asia Minor to Sicily and from Byzantium (present-day Istanbul, Turkey) to Crete. Sparked by Spartan fears about the growth of Athenian power, it continued until the Spartan general Lysander captured the Athenian fleet in 405 BC at Aegospotami and starved the Athenians into surrender in 404 BC. As a result of this victory, Athens' political power collapsed.

The Peloponnesian War was a classic example of a war between a seapower and a landpower, with Athens controlling most of the Aegean and its coasts, and Sparta most of the Peloponnese and central Greece. This partly explains both its length and why so much of the early fighting was peripheral. The Spartans were unable to bring about the decisive battle they wanted by invading Attica, since the Athenians withdrew within the fortifications of Athens and the Peiraias, their supplies guaranteed by seapower. But, equally, Athenian raids on the Peloponnesian coast were ineffective even when extended by the occupation of permanent bases on and off enemy coasts 425–424 BC, though the pressure this exerted brought about a spectacular Athenian success at Pylos in 425 BC. Following this, an Athenian attempt to win control of Megara failed, and an over-ambitious plan to knock Boeotia out of the war ended in disaster at Delium in 424 BC.

Meanwhile, the Spartans at last devised a means of hitting Athens in a vital spot when they sent an expeditionary force overland to raise revolt amongst its allies in Thrace. However, the death of its charismatic leader Brasidas and that of Cleon, the Athenian principally opposed to negotiations, at Amphipolis, led to a temporary peace in 422/1 BC.

During the early years of the peace Athens made use of the discontent of some of Sparta's allies to engineer an alliance in the Peloponnese and so match Sparta on land. The alliance disintegrated after Sparta's victory at Mantinea in 418 BC, and Athens fatally dissipated its strength by sending an expeditionary force to Sicily in 415 BC. The annihilation of this force in 413 BC shattered Athenian seapower and encouraged Sparta and its allies to make a real effort at sea, Athens' allies to rebel, and Persia to throw its financial weight behind Sparta in the hope of recovering the Asiatic Greek cities lost to Athens in the years following the Persian king Xerxes I's defeat at Plataea in 479 BC.

The great battles of the last ten years of the war were all fought at sea, in the northern Aegean, the Hellespont (present-day Dardanelles), or the Propontis (Sea of Marmara), as successive Spartan admirals strove to cut Athens' supply lines. Athens won a series of victories, notably off Cyzicus in 410 BC and the Arginusae Islands in 406 BC, but the end came with Lysander's destruction of the Athenian fleet at Aegospotami in 405 BC and, after withstanding siege by both land and sea through the winter, Athens surrendered in 404 BC.