The early career of Abdallah, the second son of the Persian general Tahir ibn Husayn, governor of Khurasan, had consisted of serving with his father in pacifying the lands of the Abbasid Caliphate following the civil war between al-Amin and al-Ma'mun.

He later succeeded his father as governor of Al-Jazira, with the task of defeating the rebel Nasr ibn Shabath, and earlier in 824 had persuaded Nasr to surrender.

He had next been sent to Egypt, where he successfully ends an uprising led by 'Abd-Allah ibn al-Sari.

He also recovers Alexandria, which had been seized seven years before by Andalusian Muslim refugees.

Abd-ar-Rahman, after his Damascus-based dynasty, the Umayyads, lost the position of Caliph in 750, had run from Abbasid persecutors for six years before arriving in Spain intent on regaining a position of power.

Defeating the existing Islamic rulers of the area,  Abd-ar-Rahman had united various local fiefdoms into an emirate in 756 to become Emir of Córdoba in the Al-Andalus (Moorish Iberia).

Eventually reaching Alexandria, they had dominated the city until their expulsion in 824, following which the refugees head to Crete.