He then went to Mecca, where he delivered the oath of allegiance that the people were to give to Ali. Al-Ma'mun also appointed Ibrahim ibn Musa, who in the meantime had lost the Yemen to Hamdawayh ibn Ali, as governor of that province and instructed Isa to assist him in reconquering it. Isa, however, remained in Mecca and gave no support to Ibrahim, who was ultimately defeated by Hamdawayh in 818 and forced to return to Mecca.[5]