The Abbasids were an Arabic dynasty that initially ruled over most of the Islamic empire (save some western parts) after assuming the caliphate in 750 CE, later on, their empire fragmented, however, they retained spiritual supremacy as caliphs until 1258 CE. They assumed the caliphal title after ousting the ruling Umayyad Dynasty, hence serving as the second dynasty to serves as a Caliphate (632-1924 CE, intermittently).
This is a companion discussion topic for the original content at https://www.worldhistory.org/Abbasid_Dynasty/.