833–842) following the failure of the previous governor 'Isa ibn Yazid al-Juludi to defeat an uprising of the tribal Arabs in the Hawf district. Umayr quickly began preparing for a campaign against the Hawfis, although he suffered a setback when 'Abdallah ibn Hulays/Jalis, who had been sent to pacify the Qaysi Arabs, defected to their side instead. Despite this, he set out from al-Fustat with his troops and the former governor 'Isa, leaving his son Muhammad in charge in his absence.[2]