What was the fundamental cause of the Peloponnesian war?

Answer 1

he underlying cause of the war was Sparta's fear of the growth of the power of Athens. This is Thucydides' own final judgment. The whole history of the rise and power of Athens in the 50 years preceding justifies this view, though the immediate occasion of the war concerned Corinth, Sparta's chief naval ally. Since the peace of 445 B.C. Pericles had consolidated Athenian resources, made Athens' navy incomparable, concluded in 433 B.C. a defensive alliance with the strong naval power Corcyra (Corinth's most bitter enemy), and renewed alliances with Rhegium and Leontini in the west. The very food supply of the Peloponnese from Sicily was endangered. In the Aegean Athens could always enforce a monopoly of seaborne trade. To this extent the Peloponnesian War was a trade war and on this ground chiefly Corinth appealed to Sparta to take up arms. The appeal was backed by Megara, nearly ruined by Pericles' economic boycott, and by Aegina a reluctant member of the Athenian Empire.

But if Sparta had not also been eager for war then peace would have lasted. Sparta was waiting an opportunity that came when Athens was temporarily embarrassed by the revolt of her subject-ally Potidaea in Chalcidice in the spring of 432 B.C. The rebel city held out until the winter of 430 B.C. and its blockade meant a constant drain upon Athenian military, and naval resources. Sparta seized the opportunity. Confident of speedy victory she refused an offer of arbitration made by Pericles. Instead, Sparta sent an ultimatum that would have practically destroyed Athenian power. Pericles urged the people to refuse and Sparta declared war.

Another Viewpoint:

Athens, having converted the anti-Persian alliance it led into an empire after peace was made with Persia, was overconfident and interfered in the affairs of other city-states outside its empire. Disputes over Potidaia and Corcyra came to a head when Athens imposed ruinous trade restrictions on Megara, a member of the Peloponnesian League led by Sparta. The League demanded these be lifted, Pericles persuaded Athens to be confident of its walls and war fleet and refuse, and war ensued.

Answer 2

A confident Athens attempted to extend its power in the Greek world. The Peloponnesian League resisted its.