The Peloponnesian War was an ancient Greek war fought between Athens and Sparta and their respective allies for the hegemony of the Greek world. The war remained undecided for a long time, until …The Peloponnesian War was an ancient Greek war fought between Athens and Sparta and their respective allies for the hegemony of the Greek world. The war remained undecided for a long time, until the decisive intervention of the Persian Empire in support of Sparta. Led by Lysander, the Spartan fleet, built with Persian subsidies, finally defeated Athens and started a period of Spartan hegemony over Greece.