The meaning of for in this text

In Athens, citizens helped to rule. Ennobled by this participation, Athenians were prepared to fight for their city-state. Perhaps this was the secret of the victory at Marathon, which freed them from Persian rule. On their way to Marathon, the Persians tried to fool some Greek city-states by claiming to have come in peace. The frightened citizens of Delos refused to believe this. Not wanting to abet the conquest of Greece, they fled from their city and did not return until the Persians had left. They were clever, for the Persians next conquered the city of Etria end captured its people.

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