Peloponnesian War
The final phase of the war is called the Decelean War, or the Peloponnesian War. In this phase, Sparta, now receiving support from the Achaemenid Empire, supported rebellions in Athens' subject states in the Aegean Sea and Ionia, undermining Athens' empire.  Eventually, Athens lost its naval supremacy.  The destruction of the Athenian fleet in a battle in 405 BC effectively ended the war, and Athens surrendered in the following year.