Reign of al-Mahdi (3 jan 775 ano – 9 jan 785 ano)
Descrição:
 During the reign of al-Mahdi, the administration of the Abbasid empire is expanded and specialized. Divisions known as Diwan are created, which are then headed by wazirs. 
Adicionado na linha do tempo:
Data:
3 jan 775 ano
9 jan 785 ano
 ~ 10 years