The
first Persian invasion of Greece, during the
Persian Wars, began in 492 BC, and ended with the decisive Athenian victory at the
Battle of Marathon in 490 BC. The invasion, consisting of two distinct campaigns, was ordered by the Persian king
Darius I 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. Darius also saw the opportunity to extend his empire into Europe, and to secure its western frontier.