What factors outside Athens helped Sparta win the war?

Several factors outside Athens contributed to Sparta's victory in the Peloponnesian War. Key among these was Sparta's alliance with Persia, which provided financial support to build a formidable navy that challenged Athenian dominance at sea. Additionally, the discontent among various city-states within the Athenian Empire, which led to revolts and defections to Sparta, further weakened Athenian resources and morale. Finally, Sparta's military discipline and effective leadership under commanders like Lysander played a crucial role in their strategic successes.