The first Persian invasion of Greece, during the Persian Wars, begins in 492 BCE and ends with the decisive Athenian victory at the Battle of Marathon in 490 BCE.

The invasion, consisting of two distinct campaigns, is 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 sees an opportunity to extend his empire into Europe, and to secure its western frontier.The first campaign in 492 BCE, led by Mardonius, re-subjugates Thrace and forces Macedon to become a client kingdom of Persia.

However, further progress is prevented when Mardonius's fleet is wrecked in a storm off the coast of Mount Athos.

The following year, having demonstrated his intentions, Darius sends ambassadors to all parts of Greece, demanding their submission.

He receives it from almost all of them, except Athens and Sparta, both of whom execute the ambassadors.

With Athens still defiant, and Sparta now effectively at war with him, Darius orders a further military campaign for the following year.The second campaign, in 490 BCE, is under the command of Datis and Artaphernes.

The expedition heads first to the island Naxos, which it captures and burns.

It then island-hops between the rest of the Cycladic Islands, annexing each into the Persian empire.

Reaching Greece, the expedition lands at Eretria, which it besieges, and after a brief time, captures.

Eretria is razed and its citizens enslaved.

Finally, the task force heads to Attica, landing at Marathon, en route for Athens.

Here, it is met by a smaller Athenian army, which nevertheless proceeds to win a remarkable victory at the Battle of Marathon.This defeat prevents the successful conclusion of the campaign, and the task force returns to Asia.

Nevertheless, the expedition has fulfilled most of its aims, punishing Naxos and Eretria, and bringing much of the Aegean under Persian rule.

The unfinished business from this campaign leads Darius to prepare for a much larger invasion of Greece, to firmly subjugate it, and to punish Athens and Sparta.

However, internal strife within the empire delay this expedition, and Darius will die of old age.

It is thus left to his son Xerxes I to lead the second Persian invasion of Greece, beginning in 480 BCE.