sentences:  However, it is not clear if Kassites were actually living in that region so late.During the later Achaemenid period, the Kassites, referred to as "Kossaei", lived in the mountains to the east of Media and were one of several "predatory" mountain tribes that regularly extracted "gifts" from the Achaemenid Persians, according to a citation of Nearchus by Strabo (13.3.6).As soldiers in foreign wars
  
  But Kassites again fought on the Persian side in the Battle of Gaugamela in 331 BC, in which the Persian Empire fell to Alexander the Great, according to Diodorus Siculus (17.59) (who called them "Kossaei") and Curtius Rufus (4.12) (who called them "inhabitants of the Cossaean mountains").