The immediate cause of the war was a dispute between Corinth and its colony, Corcyra, which led Athens to become involved. The war soon escalated to include most of the Greek world. The first phase of the war, the Archidamian War, lasted for ten years and saw Sparta invade Attica, while Athens used its navy to raid the Peloponnese. The second phase, the Sicilian Expedition, saw Athens send a massive expedition to conquer Syracuse in Sicily, which failed disastrously. The third and final phase, the Ionian War, saw Sparta receive support from the Persian Empire and gradually gain the upper hand. The war ended with the defeat of Athens in 404 BC and the establishment of Spartan hegemony over Greece.
The Peloponnesian Wars had a profound impact on Greek society and culture. The war led to a significant decline in population, and the economic and political systems of many city-states were disrupted. The war also had a profound effect on Greek philosophy and art, as artists and philosophers sought to come to terms with the violence and destruction of the war.
The Peloponnesian Wars are studied today for their historical significance and for the insights they provide into the nature of war and human behavior. The war is also considered one of the first documented instances of biological warfare, as both sides used poison gas and contaminated water supplies to attack each other.