Often enough in history, one can’t simply take things at face value. Such is the case with the unit I’d like to introduce today, one which has endured harsh, if unearned, criticism throughout history largely for its participation in a single battle. That said, by the standard of their day, this 10,000-strong unit of professional infantrymen performed the dual duties of palace guard and army backbone for one of the greatest empires the world has ever known. It’s record in combat speaks for itself throughout 200 years of uninterrupted existence despite its ultimate failure at the Hot Gates of Thermopylae. Without further ado, let’s examine the legendary “Immortals” of Achaemenid Persia.
Let’s start with the name. While not trying to ruin anybody’s day, nobody knows exactly what designation the Persians had for this unit. The name “Immortals” comes to us from none other than Herodotus, the “father of history”, and while Persian records outlining their permanent army have survived the ravages of time, none of them corroborates the name itself.
The label “Immortals” comes, according to Herodotus, from the Persian tradition of immediately replacing killed or seriously wounded members with another. Thus, the Immortals maintained the appearance of never taking casualties, heartening, no doubt, to the unprofessional levies that filled out an Achaemenid Persian army. As well, one might imagine the opposite effect upon an enemy that fought these guys one day, only to see them line up the next at full strength. A bit of deception, no doubt, that served to erode the confidence of the superstitious peoples with whom the Persians generally fought.
The Immortals were the cream of Persia’s standing army, one which may have numbered 120,000 strong, and could be quickly deployed in response to a developing situation. Messages would go out ordering local satraps and commanders to raise their forces in support, the intent being that a levied army of conscripts and locally-employed professional troops would be raised and met by hard-marching Immortals and other national troops from the capital, forming a large and potent combat force with professional soldiers at its core. The Persian network of royal roads—precursor to the vast network built by the Romans two centuries later—assured a message, and the troops themselves, could move quickly from the empire’s various capitals.
Army units, to include the Immortals, were ordered decimally, with ten regiments of a thousand men each forming a Persian division. These were led, of course, by nobility, though special care was taken in granting leadership of the division and regiments of Immortals. Over the course of the empire, which lasted from 560-330 B.C., the commander of the Immortals would come to be dual-hatted as the Chief Minister to the King.
The Immortals were armed and armored in a manner consistent with their place in Persian military society and their role as both guardians and shock troops. While they wore ceremonial robes in the Imperial Palace, at least initially, the appearance of these elite troops would change with the empire. The Immortals in Cyrus the Great’s army, (600-530 B.C.) are described as wearing bronze breastplates and helmets. By the time of the Greek Wars, however, the Immortals wore chain mail armor under linen overgarments.
Herodotus describes them as carrying both bows and spears, an interesting innovation at the time. As well, he lays out a ratio of roughly one large shield per ten soldiers, which is instructive of how the regiment would have deployed with ten ranks of a hundred men each arrayed behind a front rank of shields defended by spears. Whether or not the Immortals employed the sparabara, or wicker, man-sized shields that fit together into a mobile protective barrier, seems to remain a matter of debate. Regardless, the Immortals were prepared to fight in close quarters combat in a way not normally envisioned for other units of Persian infantry. Thus these professional troops could pour accurate and deadly fire from recurve composite bows onto an advancing foe well beyond 180 meters distant, and still be ready to deal with in close combat whoever managed to survive that murderous rain.
And their combat record was impressive indeed. The Immortals would play an important role in Cambyses’s invasion of Egypt in 525, Darius I’s invasion of India’s western frontier in 520 and again in 513, and were, of course, present at the Battle of Thermopylae in 480. Throughout all but the last engagement, the Immortals were considered to be unbeatable, and their commitment to a battle generally meant the end of said battle.
The circumstances of Thermopylae, where they were employed against a picked troop of Spartan hoplites and other Greek troops, negated their longstanding strengths and highlighted their weaknesses against fully-armored heavy infantry. That their foe was ensconced along a narrow, rocky shelf meant there was no flank to turn, no advantage to gain in maneuver, even when combined with their murderous fire. And so, the Immortals were halted—perhaps for the first time since they were first assembled—and forced to withdraw, a maneuver they accomplished in good order.
This fight, at the end of Day One of the three-day Battle of Thermopylae, has forever tarnished what may have been one of the world’s first truly elite forces. Yet the unit was not broken by their failed attempt to pierce the Greek line and, when a track was identified around the enemy position, it would be the Immortals who would force-march 14 kilometers over Mt. Callidromus to surround the Greeks and ensure Persian victory on the third day of the battle.
The Immortals would continue to serve as the steel core of the Persian army long after Thermopylae, participating in the Persian occupation of Greece through 479. They are presumed to have been destroyed along with the rest of the Persian occupation force at Plataea, though not once does Herodotus mention their presence or activities in his entire 32-page description of the battle. This makes it unclear exactly where the Immortals had gone, though it is known their commander remained with Xerxes when the latter returned to Sardis after the Battle of Salamis.
Regardless, when Alexander embarked on his mission to exterminate the Persian threat once and for all, the Immortals took the field against him at Gaugamela in 331, having retained their elite status throughout the intervening 150 years. Their reputation and martial record led Alexander to retain the unit in his own army after defeating Darius III, though likely in name only.
The Immortals, then, retain an interesting place in history. Their name—if indeed that was their name—was an early trick of psychology that clearly paid off for them. But their actions on countless battlefields ultimately helped the Achaemenid Persians become the world’s first superpower, ruling territory on three continents, stretching from modern Rumania to Pakistan and the Crimea to Sudan.
The Immortals, as a singular, formed unit, survived for 200-years, an incredible feat seldom repeated throughout all human history. They carried the torch of Persia’s first great empire until finally defeated by a spectacular individual who would, by the time of his death at the age of 33, conquer much of the known world, attaining true—not just paper—immortality.
M. G. Haynes