Arrian

Arrian of Nicomedia (; Greek: ''Arrianos''; ; ) was a Greek 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. Scholars have generally preferred Arrian to other extant primary sources, though this attitude has changed somewhat in light of modern studies into Arrian's method. Provided by Wikipedia