So perished the Great King’s most formidable enemy in Greece. With him also passed a style of leadership—unscrupulous, to be sure, but decisive and proactive—that the naturally cautious Spartans had never ceased to find alarming. Indeed, the squalid circumstances of Cleomenes’ end did much to confirm them in their suspicion of strong leaders altogether. True, Leonidas, the new king, was his brother’s successor in more ways than one, for he had married, with her father’s blessing, Gorgo, Cleomenes’ only child—as wealthy as an heiress as she had been precocious as a little girl. All the same, Leonidas remained, as a man new upon the throne and possibly tainted by fratricide, an unknown quantity: he was bound to take some time to find his feet. Who else was there, then, with the Persian hammer blow threatening, to take a lead? Leotychides? He was too busy crowing over the wretched Demaratus. The Gerousia? Or the Ephorate? Both were instinctively conservative bodies, far less likely to sanction a policy of forward defense than Cleomenes had been. Persian spies, feeding intelligence back to Sardis that winter, had much good news to report of Sparta. The turmoil in the city, the faction fighting that would have struck Darius’ strategists as so inveterately Greek, appeared to offer them their perfect opening: the opportunity to strike at Athens and take her out while she stood alone.
A chance not to be missed. In the early weeks of 490 BC, the long-awaited invasion order was finally given. A large army, “powerful and well equipped,” totaling perhaps some 25,000 men in all, marched out from Susa.35 With Mardonius still recovering from his injuries, command of the expedition was entrusted to two other generals with detailed knowledge of the western front: Artaphernes, son and namesake of the satrap in Sardis; and, as effective supremo, Datis the Mede, the seventy-quarts-a-day veteran of the Ionian revolt, and a man who, unusually for a member of the imperial elite, had such a specialized understanding of the enemy that he could actually speak some faltering Greek. The strategy these two commanders were to follow had been mapped out for them directly by the Great King: cross the Aegean with an immense armada, bring the benefits of Persian rule and peace to all the islands, and then, that objective completed, “reduce Athens and Eretria to slavery, and bring the slaves before the king.”36 The conquest of the rest of Greece, including Sparta and the Peloponnese, was to wait; and yet, even as Darius’ instructions stood, the planned expedition was an ambitious one. Certainly, as an amphibious operation, it promised to be on a scale not witnessed since the invasion of Egypt thirty-five years before. On top of that, the plan not to hug the coast but to island-hop directly to Greece was as bold and innovatory a strategy as any that even Darius had conceived.
Yet Datis and Artaphernes can have had little doubt as to their ultimate success. Every day’s journey westward brought them fresh evidence of the barely believable scale of the Great King’s resources: the labor gangs toiling to maintain the roads, whole populations sometimes, transplanted from the furthest reaches of the earth; the guards, stationed beside every bridge, every flotilla of pontoons, every mountain pass; the troops in their own rear, not merely Persians and Medes, but levies drawn from even further east, Bactrians, Sogdians and axe-wielding Saka. What was Athens to peoples such as these? Not even a name. Yet on they marched, directed by the will of their far-off, all-seeing king; and every evening, no matter where they halted, these men from the steppes, from the mountains, from the villages of Iran, they would be provisioned out of monstrous depots, supplied punctiliously with jugs of wine, and loaves of bread, and barley for their horses. And when at last, having passed through the Syrian Gates and descended into the plain of Cilicia, on the southeastern coast of modern-day Turkey, they found there waiting for them an immense fleet of ships, some built as weapons of war, others as horse transports. Up the gangplanks they climbed, men and horses alike; Datis gave the order; and the armada pulled out to sea.
Rumors of its approach were soon filtering through to Greece. No one there was unduly alarmed. Although the monstrous fleet was clearly bound for the Aegean, even to the jumpy Athenians it hardly seemed to be an imminent threat. Plenty of Persian fleets had been seen off Ionia before, after all—and they had always sailed northward, hugging the coast, on to the Hellespont. What reason to think that this fleet would take a different course? Onward the armada glided, past the ruined harbors of Miletus, toward the straits between Mount Mycale and the island of Samos—or so it appeared. But then, just by Samos, something wholly unexpected: the fleet suddenly changed its course. A shudder of disbelief passed through all those watching from the shore. The Persians were not continuing northward but heading west! There could be only one possible explanation: Datis and his task force were embarked for the open sea, for Greece—for Attica.
And as the Persian fleet fanned out across the Aegean, so its commander gave a master class in the arts of empire building. First: shock and awe. Gliding into the harbor of a startled Naxos, he took belated revenge for the debacle of the expedition there a decade previously by torching the city and rounding up the natives as slaves, dragging them onto his ships in chains as their homes and temples burned. Next: win hearts and minds. Arriving off his next port of call, the island of Delos, holy throughout the Greek world as the birthplace of Artemis and Apollo, Datis reacted to the news that the Delians had fled before his approach with injured innocence. “You men illumined by the sacred,” he expostulated, “what a strange notion of me you must have, that you run away in this manner!”37 This might have been thought a disingenuous complaint—for the Persians, after the fall of Miletus, had thought nothing of sacking the holy oracle of Didyma and carting off its great bronze statue of Apollo to Ecbatana. But the Delians were sorely mistaken if they imagined that this stern treatment of the rebels’ shrine had in any way implied disrespect for great Apollo! After all, it was the rebels themselves who had shown the god of light the grossest disrespect, by turning to the Lie and thereby surrendering his holy oracle to the night-bred pollutions of the daiva. Datis, resolved that this theological subtlety should not be lost on the Greeks, duly staged a spectacular demonstration of his devotion to the Lord Apollo, standing before the god’s altar and burning in his honor barrowloads of frankincense. Then, his point expensively made, he returned to the fleet to continue his tour of the islands, receiving their submission, taking hostages, press-ganging troops. None thought to resist him. The twin clouds of smoke—one belching black from the flames of burning Naxos, the other white and perfume-scented, rising to the nostrils of Apollo himself—had done their work. It was as though the armada, heading for Eretria and Athens, still sailed beneath their shadow—and as though that same shadow were drifting westward, inexorably, to plunge all Greece into darkness.