For others with this name, see Arrianus (disambiguation).Arrian of Nicomedia (c. 86/89 – c. after 146/160 AD; /ˈæriən/; Latin: Lucius Flavius Arrianus; Greek Αρριανός Arrianós) was born in Greece, and a historian, public servant, military commander and philosopher of the Roman period.The Anabasis of Alexander by Arrian is considered the best source on the campaigns of Alexander the Great.