Leonidas, a member of the Agiad house and married to Cleomenes' daughter, Gorgo, who possibly supports Cleomenes' aggressions against other Greek cities, in 490 succeeds his half-brother as one of Sparta's two kings.

The Messenians stage an unsuccessful anti-Spartan revolt from the fortress citadel of Mount Ithome in 490 BCE.

The First Persian War is brief.

Persia in the summer of 490, intending to punish Athens for its participation in a raid in Asia Minor, sends a force (small by Persian standards, about twenty thousand infantry and eight hundred cavalry, commanded by Datis, a Mede) that sails across the Aegean, stopping to capture the Ionian colony of Náxos, the largest of the Cyclades.

Hippias, the deposed Athenian tyrant who had taken refuge with the Persian governor at Sardis and is now a bitter old man, crosses the Aegean with the Persian army.

The seaborne invaders capture Náxos, treating the island with severity, …

…receive the submission of Andros, then continue to …

…Euboea, where they subjugate Carystus (modern Káristos) in the south and …

…destroy Eretria, enslaving and deporting its inhabitants as punishment for the five triremes sent in aid of the Ionians.

The Persians then sail south to …

…the Plain of Marathon northeast of Athens, a spot preselected by the Athenian Alcemeonid faction, led by Hippias, which hopes to be restored to power by the would-be conquerors. (The Peisistratids came originally from eastern Attica.)

The Persian army of twenty-five thousand men lands unopposed.

The Athenians are faced with the choice of marching out and confronting the Persians at Marathon or waiting for them at Athens; the decision is to be made by the Assembly.

Miltiades is well aware of the power of the Persian cavalry, which, once out on the open plain, will wreak havoc.

He is also anxious for a quick decision, because there are factions within Athens that will welcome a Persian victory in order to advance their own political ambitions.

His arguments persuade the Assembly, and the Athenian forces set out.

A runner is sent to Sparta, to seek the support of the Spartan army, but the pious Spartans reply that they will participate only at the conclusion of the sacred month of a religious festival six days later (when the moon is full).

A conflict then arises among the ten Athenian generals over whether to wait or to attack the Persians immediately.

The deciding vote is cast by the polemarchos (supreme military commander) Callimachus, whom Miltiades is able to persuade to immediate action.

The operational command of the army is to be held for one day in turn by each of the ten, but the four who have supported Miltiades surrender their right to command to him.

The Plataeans, adhering to the alliance of 519 BCE, add their troop strength of one thousand to that of the Athenians (the Tomb of the Plataeans, excavated in 1966, probably commemorates the place where they fell).

The Athenian Callias, a three-time winner of the Olympic chariot race, is a member of the Greek force, as is budding Athenian dramatist Aeschylus, who has begun to submit plays in the past decade.

Miltiades, occupying the foothills surrounding the bay, waits for a favorable moment to attack.

He chooses a time when the Persian cavalry is nonoperational, either because it has reembarked for a possible direct attack on Athens or because of some other circumstance; the reason for its absence is uncertain.

The Greeks in any case attack the Persians “at a run,” probably advancing under a under a hail of arrows.

The combination of Greek tactics, the superiority of their armor, and the new phalanx formation proves decisive.

Charging a mile across the Marathon plain, Miltiades' ten thousand Greek troops envelop—by design or topographic necessity—the Persian phalanx infantry, killing some sixty-four hundred men (and capturing seven ships) at a cost of one hundred and ninety-two Athenian dead (according to Herodotus).

The rest of the Persian force quickly embarks and put out to sea.

The Spartans arrive a couple of days later to view the corpses and depart with patronizing congratulations to the Athenians.

A Greek soldier named Pheidippedes runs (according to legend) the twenty-two and a half miles (thirty-six point two kilometers) from the Marathon battlefield to Athens, where he announces the overwhelming Greek victory over the Persians, collapses, and dies.

The Athenian army, force-marching to Athens to join the alerted citizenry, arrives in time to see the Persian fleet decline to land.

Hippias is said to have died at Lemnos on the journey home.