Who were the legendary Persian Immortals?

At the beginning of the Achaemenid Empire under Cyrus the Great in the sixth century BCE, the need for a reliable and permanent force became clear because he faced widespread rebellions and rapid territorial expansion, which required a group of elite soldiers who would remain loyal and ready at all times.

As a result, he created the Immortals. Traditionally, only Persian and Median men could join, and only those who had already proven their strength and loyalty through strict drill that demanded constant discipline were considered.

Scholars believe the Immortals may have participated in Cyrus's campaigns against the Medes, Lydians, and Babylonians, though exact records are scarce.

To enter the ranks of the Immortals, a man had to wait for a vacancy caused by death, illness, or retirement.

Then, after passing a strict selection process led by senior commanders, he would take the same position as the man he replaced.

While details on pay and conditions are limited, Herodotus suggested they had generally received better treatment than regular troops and had tended to stay close to the royal court.

Many also came from noble families who had typically trained their sons in Persian values such as archery and horsemanship. 

The Immortals also followed a clear chain of command, as officers controlled groups of ten, one hundred, or one thousand men.

The hazārapati, who generally answered directly to the king, held the office of overall commander and exercised a great deal of power.

One known hazārapati was Hydarnes the Younger, who led the Immortals at Thermopylae, who managed military duties and worked at court as one of the king's most trusted advisors.

As a result, he often played a role in succession disputes and internal state affairs.

Over time, the Immortals gradually became a status symbol among the Persian elite, and some families passed the tradition of service from father to son.

During peace, they often acted as ceremonial guards who attended royal parades and escorted the king in public.

During war, they formed the centre of the battle line and usually guarded the king’s position or pushed forward with the main advance.

Their constant presence reminded subjects and enemies alike that the king was protected and surrounded by warriors who would never hesitate to fight for him.

Rather than depend on the heavily armoured style of Greek hoplites, the Immortals relied on speed and flexibility.

Typically, they carried a short spear as their main weapon, which allowed them to strike from behind a shield wall or engage quickly in close combat.

In addition, each man wore a sword or dagger on his hip for moments when battle formations broke down. 

Many Immortals also carried bows. The Persian composite bow was made from wood, horn, and sinew and delivered powerful and accurate shots at long range.

This often gave them the ability to engage enemies from a distance before they moved forward to finish the fight at close quarters, and because of this, during large-scale battles they often opened the engagement with volleys of arrows before they charged with spears.

Their shields were made from tightly woven wicker, which gave basic protection and made them light enough for fast manoeuvres.

For clothing, the Immortals wore long tunics, trousers, and soft leather boots, which gave comfort and flexibility.

On their heads, they wore soft caps or tiaras, which were often seen in artistic depictions such as the Persepolis reliefs.

Some scholars had previously suggested rank-based decoration, but direct evidence for this is lacking.

In more formal settings, their uniforms included richly embroidered cloaks, golden jewellery, and silver-inlaid weapons, all of which presented a formal and striking appearance both on and off the battlefield.

Sometimes their equipment drew criticism from Greek writers, who saw their lighter gear as a weakness.

However, the Immortals had no intention of mimicking Greek infantry, since they trained for a different purpose.

Their strength came from mobility and flexibility and the support of the wider Persian army, which included cavalry, engineers, and archers.

At the Battle of Thermopylae in 480 BCE, the Immortals fought under Xerxes I against a small Greek force led by King Leonidas of Sparta.

After days of failed frontal assaults, a local Greek named Ephialtes revealed a hidden pass, so Xerxes ordered the Immortals to take this path and strike from behind.

Herodotus reported that Xerxes believed the Immortals would easily defeat the Spartans, but the intense fighting proved otherwise.

Their movement outflanked the Greeks and led to the fall of the pass. Greek writers focused on Spartan heroism.

Earlier, during Darius I’s invasion of Greece in 490 BCE, the Persian army suffered a major defeat at the Battle of Marathon.

Although the Immortals were among the empire's elite units, Herodotus does not mention them by name in his account of the battle.

Most modern historians believe they likely did not participate, and their involvement remains uncertain. 

In 401 BCE, the Immortals took part in the Battle of Cunaxa. Artaxerxes II, who faced rebellion from his brother Cyrus the Younger, relied on the Immortals to defend his position.

Cyrus hired Greek mercenaries who caused heavy damage to parts of the Persian army, and as a result, the Immortals protected the king and kept the line steady long enough for Cyrus to be killed in the confusion.

The Greek soldiers later retreated across Persian territory, and their journey was recorded in Xenophon’s Anabasis.

At times, the Immortals also played key roles in internal conflicts and provincial revolts, since Persian kings used them to enforce the king's orders in distant regions such as Egypt or Bactria.

Whenever the king required loyal troops who would act without hesitation, he called upon the Immortals, and, as such, over time their reputation grew from reliable service during crises rather than from a single victory.

Over the course of the fourth century BCE, the Immortals gradually lost their former power because repeated wars, internal plots, and weak leadership among Persian kings slowly eroded the discipline that had once defined them.

Too often, new recruits had entered the unit without proper training or experience, and as a result the Immortals became more ceremonial than combat-ready. 

During Alexander the Great’s invasion of Persia, some elite units continued to fight in the royal army.

While ancient sources do not definitively identify them as Immortals, it is possible that a unit that claimed descent from the original ten thousand took part in the defence.

At the Battle of Gaugamela in 331 BCE, these troops had joined Darius III’s main line but had failed to hold their position against Alexander’s assault.

The collapse of the Persian army ended the Achaemenid Empire and led to the disappearance of its most famous military unit.

After the conquest, no organised revival took place, so some former Immortals may have joined regional militias or entered the forces of Alexander’s successors.

Later, under the Sasanian Empire, a new elite force called the Pushtigban emerged.

Some Roman and Byzantine writers compared them to the Immortals, but they had no direct connection. The original ten thousand had ceased to exist.

Yet the idea of the Immortals survived in historical memory, partly because Herodotus and later Greek authors had helped preserve their image as an unbreakable force tied to the Persian king.

In many ways, they became widely seen as a symbol of imperial order, combining strict drill with elite status and a continuous presence.

But, no soldier lives forever, and the Persian Immortals created the illusion that the empire's power would not disappear.

Their legend has continued into modern times, which has included fictionalised portrayals in some graphic novels and films such as 300, where historical accuracy gave way to dramatic storytelling.