Excerpts from Books and Wikipedia
"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 became established as the leading power of Greece. The economic costs of the war were felt all across Greece; poverty became widespread in the Peloponnese, while Athens found itself completely devastated, and never regained its pre-war prosperity." [Wikipedia]