The first campaign (492 B.C.) was led by Mardonius, who re-subjugated Thrace and forced Macedonia to become a vassal of the kingdom of Persia. However, the progress of the military expedition was impeded by a storm that surprised the Persian general”s fleet while it was coasting Mount Athos. The following year, having given signs of his intentions, Darius dispatched ambassadors to all parts of Greece asking for submission. He received the same from all except Athens and Sparta, which executed the ambassadors. With Athens defiant and Sparta at war with him, Darius ordered a military campaign for the following year.
The second campaign (490 B.C.) was under the command of Datis and Artafernes. The expedition first headed for the island of Naxos, which was captured and burned, and then moved from island to island through the rest of the Cyclades, annexing them to the Persian Empire. The expedition landed at Eretria, which was besieged, and after a short period of six days, after this, captured and razed to the ground, its citizens were enslaved. Finally, the expeditionary army headed for Attica, landing at Marathon, en route to Athens. There it encountered a much smaller Athenian army, which nevertheless won an outstanding victory at the battle of Marathon.
This defeat prevented the campaign from concluding successfully, and the expeditionary force returned to Asia. Nevertheless, the expedition had achieved most of its objectives by punishing Naxos and Eretria and bringing much of the Aegean Sea under Persian rule. The unachieved goals of the campaign prompted Darius to prepare a much larger invasion of Greece to firmly subjugate it and punish Athens and Sparta. However, internal conflicts in the empire delayed the expedition, and then Darius, already advanced in age, died. His son Xerxes I led the second Persian invasion of Greece, which began in 480 BC.
For the first time, a chronicler sets out to trace the origins of a conflict not to a past so ancient or remote as to be fabulous, he does not attribute it to the wishes or whims of any god, nor to the manifest destiny of a people, but to explanations that he himself could verify.
The Ionian revolt had begun with the unsuccessful expedition against Naxos, a common enterprise of the satrap Artafernes and the tyrant of Miletus, Aristagoras. After the incident, Artafernes decided to remove Aristagoras from power; but before he could do so, Aristagoras abdicated, declaring Miletus a democracy. The rest of the cities of Ionia, on the verge of rebellion, followed in his footsteps, expelling their Persian-appointed tyrants and declaring themselves democracies as well. Aristagoras turned to the states of European Greece for support, but only Athens and Eretria offered him troops.
Greek participation in the Ionian revolt is the consequence of a complex set of circumstances, beginning with the establishment of Athenian democracy at the end of the 6th century B.C. In 510 B.C., with the help of Cleomenes I, king of Sparta, the Athenians had expelled the tyrant Hippias, who ruled the city, with the help of Cleomenes I, king of Sparta, the Athenians had expelled the tyrant Hippias, who ruled the city.Together with his father Pisistratus, Hippias” family had ruled Athens for 36 of the past 50 years.Hippias fled to the court of Artaphernes, Persian satrap of Sardis, and promised him control of Athens if he would help him regain government. Meanwhile, Cleomenes installed a pro-Spartan tyranny in Athens, personified in Isagoras, and opposed to Clisthenes, leader of the powerful family of the Alcmeonides, who considered themselves the natural heirs to the government of Athens. In a bold maneuver, Clisthenes promised the Athenians that he would install a ”democracy” in Athens, to the horror of the rest of the aristocracy. Clisthenes” reasons for suggesting such a drastic measure, which would significantly reduce the power of his own family, are unclear. It is possible that he perceived that those days of aristocratic rule would end anyway; he certainly wished by any means to prevent Athens from becoming a puppet of Sparta. Unfortunately, as a result of his proposal, Cleisthenes and his family were exiled from Athens by Isagoras, along with other dissidents. Having been promised a democracy, the Athenians seized the moment and revolted, expelling Cleomenes and Isagoras. Cleisthenes then returned to the city (507 B.C.) and began to establish a democratic government at a dizzying pace. The advent of democracy brought a revolution to Athens, which from then on became one of the great powers of Greece. The newfound freedom and self-government of the Athenians implied a further intolerance of the return of the tyranny of Hippias or any other form of subjugation, whether by Sparta, Persia or third parties.
Meanwhile, the armada reached Thasos, at the sight of which the city submitted to the Persians. The fleet followed the coastline to Acanthus in Chalkidiki, before attempting to coast the slopes of Mount Athos. There they were surprised by a violent storm, which pushed them against the cliffs. According to Herodotus, 300 ships were wrecked and 20,000 men perished.
However, Sparta suffered a series of internal machinations that destabilized its situation. The cities of Aegina submitted to the Persian ambassadors, and the Athenians, concerned that Persia might use this island as a naval base, asked Sparta to intervene. Cleomenes traveled to Aegina to deal personally with its inhabitants, but they turned to the other diarch of Sparta, Demaratus, who supported the Aeginetan resolution. Cleomenes responded by accusing Demaratus of illegitimacy, with the help of the priests of Delphi (whom he had bribed). Demaratus was replaced by his cousin Leotychidas. With the two diarchs against him, the Aegineta capitulated, giving hostages to the Athenians as a guarantee of their word. However, in Sparta it became known of Cleomenes” bribes at Delphi, and he was expelled from the city. In exile, he tried to win the support of the northern Peloponnese, at which the Lacedaemonians backed down and invited him to return to the city. Cleomenes, however, had gone too far, and in 491 B.C. he was imprisoned, accused of insanity, and died the next day. Although the official verdict was suicide, it is presumed that he was assassinated. He was succeeded by his half-brother Leonidas I.
Herodotus does not make an estimate of the size of the Persian army, indicating only that they formed a “numerous infantry in very close lines”. Among other sources, the poet Simonides, almost contemporary of the facts, counts the campaign force at 200,000 soldiers. A later writer, the Roman Cornelius Nepos estimates the figures at 200,000 infantry and 10,000 horsemen. Plutarch and Pausanias put the Persians at 300,000, the same number mentioned in the Suda. Plato and Lysias state that there were 500,000, and Marcus Junianus Justinus puts the figure at 600,000.