Persian Immortals

The Immortals (from the Greek Ἀθάνατοι) also known as Immortals Army (Persian: سپاه جاويدان) or Persian Warriors (Persian: جنگجویان پارسی) was the name given by Herodotus to an elite heavy infantry unit of 10,000 soldiers in the army of the Achaemenid Empire. This force performed the dual roles of both Imperial Guard and standing army. The force consisted mainly of Persians, but also included Medes and Elamites.

Essential questions regarding the unit (even its native name) remain unanswered, because authentic sources are missing.

Herodotus describes the 'Immortals' as being heavy infantry, led by Hydarnes, that were kept constantly at a strength of exactly 10,000 men. He stated that the unit's name stemmed from the custom that every killed, seriously wounded, or sick member was immediately replaced with a new one, maintaining the corps as a cohesive entity with a constant strength.

This elite corps is only called the 'Immortals' in sources based on Herodotus. There is evidence of the existence of a permanent corps from Persian sources, which provided a backbone for the tribal levies who made up the bulk of the Achaemenid armies. These do not however record the name of "Immortals". "Probably, Herodotus' informant has confused the name Anûšiya ('companions') with Anauša ('Immortals')", but this has been criticized by Rudiger Schmidt.

The Immortals played an important role in Cambyses II's conquest of Egypt in 525 BC and Darius I's invasion of India's smaller western frontier kingdoms (western Punjab and Sindh, now in Pakistan) and Scythia in 520 BC and 513 BC. Immortals participated in the Battle of Thermopylae 480 BC and were amongst the Persian occupation troops in Greece in 479 BC under Mardonius.

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