The prospect, then, that his army might starve, or even—perish the thought—that the royal table itself might stand empty, was a crisis of far more than mere logistics: for at risk were the very foundations of imperial prestige. Deprive the Great King of his pudding, and morale might start to plummet. Not that it was an easy matter to catch out a bureaucracy so attentive to detail that it was in the habit of issuing travel chits to ducks. Extensive preparations had been made for just such a moment of crisis as was brewing at Thermopylae. Waterfowl would certainly have been brought in the imperial baggage train, but so also would any number of the other delicacies to which the royal palate had grown accustomed: acanthus oil from Carmania, dates from Babylon, cumin from Ethiopia. Even the Great King’s drinking water had been transported in great jars from a river near Susa.
All the same, the supply of ingredients—and particularly fresh ingredients—had its limits, even for the peerless logistics chiefs of Persia. By the sixth day of the enforced halt at Thermopylae, the situation beyond the gilded confines of the royal tent, out among the teeming multitudes of the rank and file, was turning serious. The appetites of Iranians, in particular, did not readily lend themselves to belt-tightening. The Greeks, who tended to eat only the meat of animals that had first been sacrificed to the gods, told wide-eyed stories of their enemy’s carnivorous tastes. A Persian, it was said, would think nothing of baking a whole donkey by way of a birthday celebration; or even, if he were particularly well off, a camel. Soldiers on campaign took a regular supply of “oxen, asses, deer, smaller animals, ostriches, geese and cocks”34 as their daily right. The approaches to Thermopylae, never abundant in ostriches at the best of times, were proving an alarming culinary letdown to the men of the Great King’s army. Persian cooks, celebrated though they were for the inventiveness of their recipes, could hardly magically produce meals out of fields stripped wholly bare.
Yet Xerxes, though anxious about the rumbling in his soldiers’ stomachs, knew that there were others who would be feeling the pinch even worse. The presence of the Persian army on their doorstep threatened local landowners with ruin. Since responsibility for this regrettable state of affairs clearly stopped with Leonidas and his pestilential little army, the obvious—indeed, the only—way for the natives to spare themselves utter destitution was to help the Great King flush the Hot Gates clear of its obstruction. Surely, then, Xerxes had to trust, where the spectacle of royal invincibility had so far failed to recruit a guide, self-interest was bound to succeed?
And so in the end it did, as, amid the dust and disappointments of the second day’s fighting, the Greek capacity for backstabbing came to the rescue of the Persian high command. For almost a week the imperial army had been encamped before Thermopylae—and now, at last, an informant was brought cringing into the royal tent. His name was Ephialtes, a native of the plain on which the Persian army was camped, and he it was who revealed to his interrogators that Callidromus did indeed possess a secret. “In the hope of a rich reward, he told the king about the trail which led over the mountain to Thermopylae”35—and even offered, in the truly fatal act of treachery, to serve the invaders as their guide.
Immediately the fearsome machinery of the imperial army was set into smooth and deadly motion. Late in the day though it already was, further delay was clearly out of the question: the ascent of Callidromus was ordered for that very night. Nor was it to be attempted by the light infantry that Leonidas had presumed would be the only troops capable of making such a journey. The Immortals, their toughness bred amid the uplands of Iran, were a squad made for such an adventure. Bloodied the previous day in the pass, there was not a man among them who would not have relished his chance of revenge. For their commander, in particular, the mission had a particular piquancy. Hydarnes was son and namesake of the coconspirator with Darius who, forty-one years previously, had held the Khorasan Highway against a vast army of rebel Medes. Now, given the perfect opportunity to add to his family’s battle honors, Hydarnes would serve Darius’ son, not by holding, but by clearing a vital pass.
He and his ten thousand men left at dusk. Their route began several miles west of the Hot Gates, west too of Trachis and of the Asopus gorge above which it stood.36 Behind them, as they began their ascent, watch fires were already starting to dot the plain, but soon the view of the camp was lost. Fortunately, just as Ephialtes had said it would be, the trail was easy to follow, and the moon, the fateful Carneian moon, full in a cloudless sky, outshone even the brilliance of the August stars. For hours the Immortals marched, through silver light and shadow, swinging left across the broad plain which stretched beyond the high cliffs of Trachis, down into a valley and then over the River Asopus. Here, beyond the far bank, the way at last grew steeper. Even now, however, despite being weighed down by shields and armor, the Persians could still make their ascent without zigzagging, and after an hour or so, breasting a fringe of oaks and pines, they reached the edge of another wide plateau. Ahead of them, past more woods, and over occasional stretches of open grass, the path wound on, still climbing, but gently once more, and the Immortals, picking up speed again, began to round the peak that now loomed between them and Thermopylae. Between them and their view of the eastern horizon, too. But gradually, as the stars began to fade, so the marching Persians could sense the coming of morning, and that the sun, bright with the eternal beauty of Ahura Mazda, would soon be rising over the Hot Gates. The gradient began to flatten out. The Immortals passed into a wood of oaks. Even beneath the trees, however, the way ahead of them remained perfectly visible, for not only was it growing lighter by the minute, but the recent gales had swept bare the trellis of branches above them. The leaves, already dry, crackled underfoot. Then, above the rustling and the tramping of ten thousand pairs of feet, there came a sudden ringing: the sound of metal.
Stepping forward to the edge of the trees, the Immortals’ commander saw, to his consternation, a garrison of hoplites blocking his path. He had clearly taken them by surprise, for the Greeks were still struggling to pull on their armor; but Hydarnes, who had learned the hard way not to underestimate the Spartans, wanted his rematch with them at the Hot Gates, not on the heights above the pass. When Ephialtes, however, pointing to the lack of scarlet tunics and cloaks among the enemy, reassured his master that he was not facing Leonidas’ men, but the soldiers of another city, most likely Phocis, Hydarnes immediately gave his men the order to attack. Drawing their bows, the Immortals duly fired a withering volley at the half-formed phalanx. The Phocians, lacking the strategic good sense that would have been supplied to them, perhaps, by the presence of a Spartan officer, and taking it for granted that the barbarians had marched through the night with the specific goal of wiping them out, retreated chaotically to the top of a nearby hill. Here they steeled themselves to make a heroic final stand—only to see the Immortals sweep contemptuously past them, and continue along the open path.