a strategy that avoided land battles and relied instead on control of the sea. When the war broke out, most Athenians crowded into the city, leaving the outlying areas of Attica open to invasion. Sparta's strategy was to invade yearly, as it did from 431 to 425 (except in 429 and 426), hoping to break Athens's will and to encourage Athens's subjects to rebel.
The first stage of the war, called Archidamian from Archidamus, the Spartan king, ended in a stalemate in 421 with the Peace of Nicias. Athens had remained firm and had suppressed the dangerous rebellion of Mytilene in 427. Athens was most damaged by the onset in 430 of plague, which removed perhaps a quarter of the Athenian population and caused Pericles' death in 429. Athens gained an advantage in the war in 425 by capturing a Spartan force on the island of Sphacteria, but this victory was canceled the next year when the Spartan Brasidas captured Amphipolis. The deaths in 422 of Cleon and Brasidas, both of whom were prowar, led to a truce the next year. The peace was unstable because, although there were no significant hostilities, neither side fully complied with the terms of the agreement.
In 415, a year after destroying the inoffensive island state of Melos, Athens attempted to conquer Syracuse, largely at the urging of Alcibiades. The expedition ended disastrously in 413, and the debacle enticed Sparta into fighting once more. This last stage of the war is called "Decelean" from the name of a town in Attica, Decelea, which Sparta fortified, to the enormous cost of the Athenians. However, the war was won on the sea. Aided by Persian resources, Sparta became a naval power and encouraged the rebellion of Athens's allies. Proceeding north from Chios to the Hellespont, Sparta gradually overcame the Athenian navy in spite of
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