813–833), Yazid was appointed governor of the Yemen by al-Ma'mun's general Tahir ibn al-Husayn, with a directive to bring the province under al-Ma'mun's control. He accordingly set off for the Yemen with a large body of horsemen, and upon his arrival he convinced the Yemenis to abandon al-Amin and swear allegiance to al-Ma'mun instead. He quickly ran into problems, however, with his policy of supporting the Qahtanite Arabs of the province at the expense of the local abna, who he treated in an extremely harsh manner.