The first Persian invasion of Greece took place from 492 BC to 490 BC, as part of the Greco-Persian Wars. It ended with a decisive Athenian-led victory over the Achaemenid Empire during the Battle of Marathon. Consisting of two distinct campaigns, the invasion of the independent Greek city-states was ordered by the Persian king Darius the Great, who sought to punish Athens and Eretria after they had supported the earlier Ionian Revolt. Additionally, Darius also saw the subjugation of Greece as an opportunity to expand into Southeast Europe and thereby ensure the security of the Achaemenid Empire's western frontier.