Haroon al Rashid worked towards fool-proofing his succession arrangement more than any other caliph by far: the ceremony he held at Mecca with his heirs swearing to abide by his wishes is more elaborate than anything we have or will come across. He would not have gone to such lengths if he didn’t think it necessary, and it wasn’t long before his sons proved him right. Eager for more power, Al Amin’s advisors urged him to move against his brothers, leading the entire caliphate down a dangerous path.