Peloponnesian War Begins

In 431 BCE, the long rivalry between Athens and Sparta broke into open warfare, beginning a conflict that would last, with a brief pause, until 404 BCE. The Peloponnesian War pitted the Athenian maritime empire against the Spartan-led Peloponnesian League, drew in much of the Greek world, and left the most dynamic city-states of the age exhausted and weakened. It also produced one of history's great works of analysis, Thucydides' account of the struggle.

The roots of the war lay in the half century after the Greek victory over Persia. Athens had led the Delian League, an alliance created to continue the fight against Persia, and gradually turned it into an empire in which allies paid tribute and were prevented from leaving. Sparta, the leading land power, headed a looser alliance of Peloponnesian states and grew uneasy at Athenian growth. Thucydides, our main source, argued that the deepest cause was the rise of Athenian power and the fear it inspired in Sparta. Earlier clashes in the 460s and 450s, followed by a truce known as the Thirty Years' Peace of 446 BCE, had failed to settle the matter.

Several disputes in the 430s pushed the two sides toward war, among them the quarrel between Corinth and its colony Corcyra, in which Athens became involved, and the Athenian siege of Potidaea. Corinth pressed Sparta to act, and the Spartans concluded that Athens had broken the peace. The fighting itself is usually said to have started in 431 BCE, when Thebes, a Spartan ally, attacked the small city of Plataea, which was allied with Athens.

The early strategy reflected each side's strengths. Sparta invaded Attica almost every year, hoping to force the Athenians into a land battle. Athens, guided by Pericles, retreated behind its walls, relied on its navy and imported supplies, and raided the Peloponnesian coast. A devastating plague struck the crowded city around 430 BCE and killed many people, Pericles among them. The first phase ended with the Peace of Nicias in 421 BCE, which proved unstable. Athens then launched a disastrous expedition to Sicily in 415 BCE, losing much of its fleet and army. With Persian financial help, Sparta built a navy of its own and finally destroyed the Athenian fleet at Aegospotami in 405 BCE. Athens surrendered the following year.

The consequences were profound. Athens lost its empire and walls, and its democracy was briefly replaced by an oligarchic regime. Sparta gained supremacy, but its dominance was short-lived, soon challenged by Thebes and others. The war encouraged brutality and political upheaval across Greece, and the weakened city-states later proved easy prey for Macedon. Its enduring intellectual legacy is Thucydides' history, still studied for its insights into power, fear and the dynamics of war.