WI: Harun al-Rashid doesn't divide his empire

[Night Gaul]

Harun al-Rashid, the fifth Abbasid Caliph, ruled during the zenith of the Islamic Golden Age, and played a major role in turning Baghdad into one of the great centers of learning and commerce. In 802, he decided to divide his vast empire between three of his sons: al-Amin, al-Ma'mun, and al-Qasim ibn Harun al-Rashid, with al-Amin being the one overall in charge. Not long after Harun's death, a civil war known as the Fourth Fitna broke out between the former two over control of the empire.

What if he hadn't divided his territories?

 

[Nivek]

The proto shia will do a great rebellion but without a real division they could beat them and keep with the Abassadid caliphate for a long time