Abdallah ibn Tahir al-Khurasani

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).

His grandson, Al-Hakam, Umayyad Emir from 796 until 822, had crushed a rebellion led by clerics in a suburb called al-Ribad on the south bank of the Guadalquivir river and punished the inhabitants by exiling them by ship.

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

Crete, as the target of Muslim attacks since the first wave of the Muslim conquests in the mid-seventh century, had in 654 suffered a first raid in 674/675 another; parts of the island had been temporarily occupied between 705 and 715 during the reign of the Umayyad Caliph al-Walid I.

The island had never been conquered, however, and despite occasional raids in the eighth century it has remained securely in imperial hands; a quiet cultural backwater, Crete is too distant from the Arab naval bases in the Levant for an effective expedition against it to be undertaken.

A group of Andalusian exiles at some point in the second half of the reign of Emperor Michael II, who reigns from 820 to 829, land on Crete and begin its conquest.

These exiles, with a long history of wanderings behind them, are the survivors of a failed revolt in 818 against the emir Al-Hakam I of Córdoba.

In the aftermath of its suppression, the citizens of the Cordovan suburb of al-Rabad had been exiled en masse.

Some had settled in Fez in Morocco, but others, numbering over ten thousand, had taken to piracy, probably joined by other Andalusians.

Some of the latter group, under the leadership of Umar ibn Hafs ibn Shuayb ibn Isa al Balluti, commonly known as Abu Hafs, had landed in Alexandria and had taken control of the city until 827, when they had been besieged and expelled by the Abbasid general Abdullah ibn Tahir al-Khurasani.

The exact chronology of their landing in Crete is uncertain.

Following the Muslim sources, it is usually dated to 827 or 828, after the Andalusians' expulsion from Alexandria.

Byzantine sources, however seem to contradict this, placing their landing soon after the suppression of the large revolt of Thomas the Slav (821–823).

Further considerations regarding the number and chronology of the campaigns launched against the invaders and prosopographical questions of the imperial generals that headed them have led other scholars like Vassilios Christides and Christos Makrypoulias to propose an earlier date, around 824.

The Andalusians and their families, under the terms of their agreement with Ibn Tahir, had left Alexandria in forty ships.

Historian Warren Treadgold estimates them at some twelve thousand people, of whom about three thousand would be fighting men.

The Andalusians according to Byzantine historians were already familiar with Crete, having raided it in the past.

They also claim that the Muslim landing was initially intended as a raid, and was transformed into a bid for conquest when Abu Hafs himself set fire to their ships.

This is probably later invention, however, as the Andalusian exiles had brought their families along.

The Andalusians' landing-place is also unknown; some scholars think that it was at the north coast, at Suda Bay or near where their main city and fortress Chandax (”Castle of the Moat", modern Heraklion) will later be built, but others think that they most likely landed on the south coast of the island, then moved to the more densely populated interior and the northern coast.

Archbishop Cyril of Gortyn is assassinated and his city so thoroughly devastated it will never be reoccupied.

Iran’s native Tahirid dynasty, which had come to power in 821, rules increasingly independent of the Abbasid caliphate’s central government.

The lands in the east of Persia that had been awarded by Caliph al-Ma'mun to the dynast Tahir ibn Husayn, who had been succeeded on his death in 822 by his son Taljha, will subsequently be extended by his successors as far as the borders of India until their overthrow by the Saffarid dynasty, who in 873 will annex Khurasan to their own empire in eastern Persia.

Talha’s governorship had lasted until 828.

Tahir's other son, Abdullah, had been instated as the wali of Egypt and the Arabian Peninsula, and when Talha died in 828, he had been given the governorship of Khurasan.

Although Abdallah had been made the governor of Khorasan following his brother's death in 828, he had only arrived in Nishapur in 830; in the meantime he had been busy fighting more revolts.

He had been assigned for a brief time in 829 to stop the Khurramite Babak, but then was given new orders by the caliph to move to Khurasan and stop the Kharijites.

Abdallah's brother 'Ali had acted as deputy governor of Khurasan until he was ready to take up residence in Nishapur.

Abdullah is considered one of the greatest of the Tahirid rulers, as his reign witnesses a flourishing of agriculture in his native land of Khurasan, popularity among the populations of the eastern lands of the Abbasid caliphate, and the extension of Khurasanian influence due to Abdullah’s experience with the western parts of the caliphate.