The Peloponnesian War a. broke out when Greece was united under Pericles.
b. was the result of the plague.
c. began because older Spartans wanted to return to fighting.
d. began with quarrels over trade.

The Cause of the Peloponnesian War

The formation of the Delian League, or Athenian League, in 478 B.C. united several Greek city-states in a military alliance under Athens, ostensibly to guard against revenge attacks from the Persian Empire. ... It became a 15-year conflict between Athens and Sparta and their allies.

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