It is not evident in medieval Muslim sources when Muhanna died or when the post of "amir al-ʿarab" was stripped from him. It is known for certain that prior to the Mamluk conquest of Syria in 1260, the "amir al-ʿarab" was Muhanna's uncle Ali ibn Haditha. The circumstances of Isa's replacement of Ali are also unclear. In some versions, Isa was appointed by Sultan Qutuz as a reward for his support in the Battle of Ain Jalut against the Mongols in the latter half of 1260, though the sources indicate that Isa and his Bedouin horsemen refrained from actually participating in the battle. In another version, Qutuz's successor Baybars appointed Isa as a reward for assisting him during his 1250s exile in Syria (in this version, Ali was stripped of the title as punishment for denying Baybars refuge). In any case, it is known that Baybars issued a diploma confirming Isa as "amir al-ʿarab" and recognizing his "iqtaʿat" (fiefs) in 1260/61. Among his "iqta'at" were half of Salamiyah, which was separated from the "iqtaʿ" of Hama, and Sarmin. Baybars also entrusted the Al Fadl and the other Bedouin tribes of the Syrian desert and steppe with guarding the Syrian frontier with Mongol Ilkhanid-held Iraq.