Battle of Anzen: The Byzantine emperor Theophilos suffers a heavy defeat by the Abbasids.

The Battle of Anzen or Dazimon was fought on 22 July 838 at Anzen or Dazimon between the Byzantine Empire and the forces of the Abbasid Caliphate. The Abbasids had launched a massive expedition with two separate armies in retaliation for the Byzantine emperor Theophilos's successes the previous year, and aimed to sack Amorion, one of Byzantium's largest cities. Theophilos with his army confronted the smaller Muslim army, under the Iranian vassal prince Afshin, at Dazimon.

Theophilos was Byzantine Emperor from 829 until his death in 842. He was the second emperor of the Amorian dynasty and the last emperor to support iconoclasm.

The Abbasid Caliphate or Abbasid Empire was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib, from whom the dynasty takes its name. After overthrowing the Umayyad Caliphate in the Abbasid Revolution of 750 CE (132 AH), they ruled as caliphs based in modern-day Iraq, with Baghdad being their capital for most of their history.