Answer:
Key aspects of the Peloponnesian War:
1) It was caused from the ongoing rivalry between the city states of Athens and Sparta. Sparta had created the Peloponnesian league with its main city states as Sparta, Corinth, Elis, and Tegea.
2) Athens had bullied other city states into joining the Delian League, with its main city states as Athens, Aegina, Byzantium, Naxos, and many more.
3) The Peloponnesian War lasted from 431-405 B.C.E. Athens and Sparta had made a peace treaty: Peace of Nicias, stating that the two city states would defend one another for the next 5 decades, but the treaty only lasted for six years.
4) The Spartan general Lysander had defeated the Athenians at Aegospotami, making Athens surrender. With the Peloponnesian War ending, at the same time was the end of Ancient Greece's golden age.