The Daylamites first appear in historical records in the late 2nd century BCE, where they are mentioned by Polybius, who erroneously calls them Elamites () instead of Daylamites (). In the Middle Persian prose Kar-Namag i Ardashir i Pabagan, the last ruler of the Parthian Empire, Artabanus V (r. 208-224) summoned all the troops from Ray, Damavand, Daylam, and Padishkhwargar to fight the newly established Sasanian Empire. According to the Letter of Tansar, during this period, Daylam, Gilan, and Ruyan belonged to the kingdom of Gushnasp, who was a Parthian vassal but later submitted to the first Sasanian emperor Ardashir I (r. 224-242).