The Immortals (from the Greek Ἀθάνατοι, sometimes Ten Thousand Immortals or the Persian Immortals) was the name given by Herodotus to an elite force of soldiers who fought for the Achaemenid Empire. This force performed the dual roles of both Imperial Guard and standing army during the Persian Empire's expansion period and during the Greco-Persian Wars. Its Persian name may have been Anûšiya ("companions"; perhaps confused with Anauša 'immortals' from an- 'non' + auša 'death'). The force consisted mainly of Persians but also included Medes and Elamites.