Origins
The Persian Immortals (Greek: Athanatoi) were the elite infantry corps of the Achaemenid Persian Empire, established by Cyrus the Great during his conquest of the ancient Near East in the mid-6th century BCE. Our primary knowledge comes from the Greek historian Herodotus, who wrote that the Persians called this force “the Immortals” because their number was always maintained at exactly 10,000—whenever a member was killed, wounded, or fell ill, he was immediately replaced, giving the impression that the unit could never be diminished and was therefore immortal.
The Immortals emerged from Cyrus’s need for a reliable core force during his rapid expansion. Conquering the Median Empire (550 BCE), Lydia (546 BCE), and Babylon (539 BCE) required not only battlefield effectiveness but also a formation loyal to the king personally amid the shifting allegiances of a multiethnic empire. The Immortals served this dual function: as shock troops in battle and as the king’s personal bodyguard, they combined military utility with political security.
The unit drew its members from the Persian and Median nobility, though the exact recruitment criteria remain unclear. Some scholars believe membership was hereditary; others suggest it was awarded for military distinction. What is certain is that the Immortals enjoyed privileged status—they received the best equipment, supplies, and compensation. Their families accompanied them on campaign with elaborate baggage trains, a luxury denied to regular troops. This combination of elite status, constant strength, and personal proximity to the king made them the Achaemenid Empire’s most prestigious military formation.
Structure & Function
The Immortals were organized as a division of exactly 10,000 men, commanded by a general (hazarapatis) who ranked among the empire’s highest military officials. The force was subdivided into ten battalions of 1,000, each led by a hazarapat, and further into companies of 100 (under satapatis) and squads of 10 (under dathabam). This decimal organization reflected broader Persian administrative practice and facilitated precise command and control.
Within the 10,000, a further elite existed: 1,000 men, sometimes called the “Apple Bearers” (melophoroi) from the golden apple counterweights on their spear butts, served as the innermost royal guard. These soldiers accompanied the king everywhere and had access to his person. They carried distinctive golden pomegranate ornaments and wore especially elaborate dress, visually distinguishing them from the other 9,000 Immortals.
The Immortals’ equipment reflected their dual role as combat troops and ceremonial guards. They wore ornate robes over scale armor, carried wicker shields (spara), short spears, and powerful composite bows. In battle, they typically formed the Persian center, using archery to weaken enemy formations before closing for hand-to-hand combat. Their effectiveness depended on overwhelming numbers and combined arms—the Immortals were often deployed alongside cavalry, supporting their charges or exploiting breaches. Against Greek hoplites at battles like Thermopylae and Plataea, however, their lighter equipment proved a disadvantage in close combat.
Historical Significance
The Immortals were central to Achaemenid military success for over two centuries. They participated in every major campaign of imperial expansion and consolidation, from Cyrus’s conquests through Darius I’s invasion of Scythia and Greece to Xerxes’ massive expedition against Athens and Sparta. At Thermopylae (480 BCE), Immortals led by Hydarnes discovered the mountain path that enabled the Persians to outflank the Spartan-led Greek defenders—the battle’s decisive moment. Though often overshadowed in Western narratives by their Greek opponents, the Immortals were the backbone of the empire that ruled the ancient world’s largest domain.
The unit embodied key aspects of Achaemenid imperial ideology. Their name and constant strength symbolized the empire’s permanence and the king’s inexhaustible resources. Their ceremonial splendor displayed Persian wealth and cultural sophistication. Their multinational composition (later including subject peoples alongside Persians and Medes) represented the empire’s claim to universal sovereignty. When Alexander the Great conquered Persia, he recognized the Immortals’ symbolic importance by creating his own 10,000-strong Macedonian unit and later incorporating Persian nobles into a new royal guard.
The Immortals’ legacy extended far beyond the Achaemenid period. Subsequent Persian empires revived the name and concept: the Sasanians maintained elite units called “Immortals,” and in 1941, Mohammad Reza Shah Pahlavi established the Imperial Guard of Iran under the same name. The romantic image of the 10,000 ever-replenished warriors has captivated Western imagination since Herodotus, appearing in countless works of literature, art, and film. The Immortals represent the archetype of the elite royal guard—fearsome in battle, magnificent in appearance, and eternally at full strength.
Key Developments
- c. 550 BCE: Cyrus the Great establishes the Immortals during Persian Empire’s founding
- 550 BCE: Immortals participate in overthrow of Median Empire
- 546 BCE: Conquest of Lydia; Immortals help defeat King Croesus
- 539 BCE: Capture of Babylon; Immortals enter the ancient city
- 530 BCE: Death of Cyrus; Immortals continue under Cambyses II
- 525 BCE: Conquest of Egypt; Immortals form core of invasion force
- 522 BCE: Immortals support Darius I’s seizure of throne from Bardiya (or Gaumata)
- 513-512 BCE: Immortals accompany Darius on Scythian expedition into Europe
- 490 BCE: Battle of Marathon; Immortals not present at Persian defeat
- 480 BCE: Xerxes’ invasion of Greece; Immortals discover path at Thermopylae
- 480 BCE: Battle of Thermopylae; Immortals outflank Greek defenders
- 479 BCE: Battle of Plataea; Immortals suffer heavy casualties against Greek hoplites
- 465 BCE: Immortals involved in Artabanus’s assassination of Xerxes I
- 401 BCE: Battle of Cunaxa; Immortals fight against Cyrus the Younger’s rebellion
- 330 BCE: Alexander defeats last Achaemenid forces; Immortals cease to exist as Persian institution