Themistocles, whose father, Neocles, came of the aristocratic Lycomid family and was not poor, but whose mother was a concubine, non-Athenian, possibly non-Greek, thus owes his citizenship to the legislation of Cleisthenes, which, in 508, had made citizens of all free men of Athens.

Elected archon in 493, he sponsors the first public works destined to make the defensible rocky bays of Piraeus, five miles from Athens, into harbors, replacing the nearer but unprotected beaches of Phaleron.

Miltiades, having arrived in Athens, is bound to raise animosities here because of his fabulous wealth, his foreign wife Hegesipyle (who bore him a son, Cimon the younger, about 510), and his past as a “tyrant”.

As archon, Themistocles must be concerned in the trial of Miltiades, who is prosecuted for his tyrannical role in the Chersonese, probably at the instigation of the rival clan of the pro-Persian Alcmaeonids, but he is triumphantly acquitted as the champion of resistance to Persian encroachments upon Greek freedom.

Having firsthand experience of the Persians, Miltiades is chosen, from 493 onward, as one of the ten generals of the Athenian land forces.

Unlike Themistocles, he is still thinking in terms of land warfare and of an agreement with Sparta, which is favored by the Athenian landowners, the peasantry, and the rural middle class.

Persian king Darius the Great before the Scythian campaign of 513-512 according to Herodotus had sent ships to explore the Greek coasts, but he takes no military action until after Athens and Eretria support the Ionian revolt, which Darius takes as a pretext for launching an invasion of the Greek mainland.

After the suppression of the rebellion, Mardonius, Darius' son-in-law, is given charge of an expedition against Athens and Eretria, but the loss of his fleet in a storm off Mount Athos in 492 BCE forces him to abandon the operation.

Two royal families hold the kingship of Sparta, whose ruling class has devoted itself to war and diplomacy from the fifth century on, deliberately neglecting the arts, philosophy, and literature, and forging the most powerful army standing in Greece.

Cleomenes, the Agiad king, tries in 491 to punish the Medizers of Aegina for that city's submission to the Persians, but co-king Demaratus again thwarts him.

Cleomenes engineers the deposing of Demaratus on a false charge of illegitimacy by bribing the Delphic oracle, and Demaratus' cousin Leotychidas of the Eurypontid house accedes to the throne.

Cleomenes' deceit is discovered, and he flees to Thessaly.

The Spartans reinstate him, but soon afterwards, he goes insane (it is alleged), is imprisoned, and commits suicide.

The deposed Demaratus has in the meantime fled to Persia and is given some small cities in northwestern Asia Minor (which his descendants will continue to hold in the time of Xenophon, nearly a century later).

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.