What impact did the Peloponnesian war have on ancient greece

Athens, was the strongest city-state in Greece before the war, while Sparta was established as the leading power of Greece after/during the war.

The Peloponnesian War reshaped the Ancient Greek world. On the level of international relations, Athens, the strongest city-state in Greece prior to the war's beginning, was reduced to a state of near-complete subjection, while Sparta was established as the leading power of Greece.