The battle of Thermopylae saw 300 Spartans hold back a massive Persian army. But who were the soldiers that faced off against King Leonidas and why were they called The Immortals when they were so obviously mortal? Why were they so feared by the enemies that they went up against?
The information that exists about The Immortals is somewhat sparse. It is known that they were troops that fought for the Achaemenid Empire which ws in power in Persia from 550 BCE to 330 BCE. Persia was a true force to be reckoned with. Although the Persians were nomadic originally, they settled on a plateau in southwest Iran. From there, they expanded outward until finally, under the leadership of Cyrus the Great, the empire stretched from the Indus Valley (the eastern boundary of the empire) to the northeastern border of Greece. During its growth, the Persian Empire managed to absorb Egypt, Macedon and Thrace and had absorbed the Median, Lydian and Babylonian Empires.
It is known that these were the elite troops of the Persian Empire. They had several different functions besides taking on Spartans. One was to act as heavy infantry while on duty with the standing army and the other was to act as part of the Imperial Guard.
Because the unit was expected to act as infantry in the standing army they were outfitted as such. The Immortals carried shields and weapons such as spears, swords, bows and arrows and daggers. These allowed them to be very versatile in combat. They wore scale armor which was topped by rich clothing. The Immortals were elite troops. Because of this they were often showered with gold and this showed clearly in the clothing they wore and the equipment that they travelled with. Unlike other troops, the Immortals were allowed to bring women and servants with them. These non-combatants travelled in covered wagons and were dressed very elaborately. The Immortals even received special food that was not given to the remainder of the army.
The uniform of the Immortals was made up of an embroidered, sleeved tunic, scale mail and trousers. They wore tiaras and soft felt caps on their heads. They were armed with short spears, short swords and bows and arrows. In addition to their scale mail shirts they were protected by a wicker shield that each man carried.
Much of the information we have on this unit comes from the writings of Herodotus, a Greek historian who lived from 484 BCE to 425 BCE. He stated that the Immortals always numbered ten thousand men and that any time there was a vacancy (whether due to illness or death) it was instantly filled. The unit was exclusive and soldiers had to apply to join it. They were only accepted if they were of Persian, Elamite or Median ethnicity.
In addition to the battle of Thermopylae, the Immortals also participated in other battles. In 547, they participated in the conquest of the Neo-Babylonian Empire by Cyrus the great and took part in the Egyptian campaign mounted by Cambyses in 525 BCE. In 520 BCE and 513 BCE, the Immortals also took part in fighting in Scythia under Darius the Great.