How did Persian money help Sparta defeat Athens in 404 BCE?

During the final phase of the Peloponnesian War, the Achaemenid Empire provided critical financial support that allowed Sparta to challenge and eventually dismantle Athenian naval supremacy.1

Following the Athenian defeat in Sicily, the Persian king Darius II decided to back Sparta, viewing a weakened Athens as beneficial to Persian interests in Anatolia. The young prince Cyrus the Younger was appointed as satrap of Lydia and commander of Achaemenian forces in Asia Minor in 407 BCE. He formed a close, strategic alliance with the Spartan commander Lysander, providing the necessary funds to maintain and rebuild the Spartan fleet.12

This infusion of Persian wealth enabled Sparta to sustain its naval operations, leading to the decisive victory at the Battle of Aegospotami in 405 BCE. By 404 BCE, the lack of resources and the loss of its fleet forced Athens to surrender, resulting in the demolition of its Long Walls and the end of its empire.1