Answer: Because they had heard about the Spartan defeat at Thermopylae, and thought the Persians would destroy Athens. How were the Greeks able to defeat the Persian fleet, even though they were outnumbered?The invasion, consisting of two distinct campaigns, was ordered by the Persian king Darius the Great primarily in order to punish the city-states of Athens and Eretria. These cities had supported the cities of Ionia during their revolt against Persian rule, thus incurring the wrath of Darius.
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