Abbasid Caliphate and Byzantine Empire

The Abbasid Caliphate or Abbasid Empire was the third Islamic caliphate, ruled by the Abbasid dynasty. The dynasty was descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib (d. 653), after whom it is named. The Abbasids rose to power in 750, when the Abbasid Revolution overthrew the preceding Umayyad Caliphate. They ruled as caliphs from their base in Iraq until 1258, with Baghdad as their capital for most of their history.

The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Eastern part of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived the fall of the Western Roman Empire in the 5th century AD, it endured until the fall of Constantinople to the Ottoman Empire in 1453. The term 'Byzantine Empire' was coined only after its demise; its citizens used the term 'Roman Empire' and called themselves 'Romans'.