Which Greek city-state defeated Athens in the Peloponnesian War? Sparta defeated Athens in the Peloponnesian War, which ended with Athens surrendering in 404 BC.
The conflict lasted from 431 to 404 BC and pitted the Peloponnesian League, led by Sparta, against the Delian League, dominated by Athens. Athens possessed a powerful navy and relied on its maritime empire, while Sparta was renowned for its disciplined land army. The war was not a single uninterrupted campaign; it included truces, renewed fighting, shifting alliances, and major disasters.
A devastating plague struck Athens early in the war and killed many inhabitants, including the statesman Pericles. Later, the disastrous Athenian expedition against Syracuse weakened Athens severely. Sparta eventually built a navy with Persian financial support and defeated the Athenian fleet at Aegospotami in 405 BC. Athens then surrendered, its long walls were dismantled, and Sparta became the leading Greek power, although its dominance was temporary.