The Peloponnesian War was won by Sparta because A. their alliance with the Persian Empire helped win the war against Athens.
In the 5th Century BC, the Peloponnesian War broke out between Athens and her allies and Sparta and her allies because:
As war raged, the Persians got involved on the side of the Spartans because they were worried about Athens's influence in Persian held Greek areas. They gave the Spartans money and took over Delian League areas.
In conclusion, Sparta allied with the Persians to defeat the Athenians because both powers feared the might of Athens.
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