Greece was now organized into two armed camps, the land-based Peloponnesian League led by Sparta and the sea-based Delian League by Athens. Yet the Athenians adopted a defensive policy advocated by Pericles, who recognized that the Spartans were superior to the Athenians on land but could not challenge them on the sea. The standoff continued for several years and the cramped conditions inside the city led to an epidemic that killed at least one-fourth of the population, including Pericles. Pericles nephew, who in 415 b.c.e convinced Athenians to invade Syracuse an ally of the Spartans.
When the subject city-states that made up the Athenian empire learned of the disaster, many of them rebelled. A short-lived oligarchy took control of Athens in 411 b.c.e during the upheaval. Although democracy was sson restored, the humbled Athenian fleet could not longer effectively prosecute the war, for the Spartans now had an effective fleet of their own, paid for by the Persians, who took advantage of the war in Greece to play their former enemies against one another. Finally in 404 b.c.e the Athenians surrendered. An oligarchy known as the Thirty Tyrants, friendly to Sparta, took control of the city. With the defeat of Athens, the Classical culture of the Greeks declined.