The Banu Hilal invade Ifriqiya

The Banu Hilal and Banu Sulaym were Arab Bedouin from Najd, some of whose clans had moved into Egypt, Iraq and Syria. After they joined the Qarmatians against the Fatimids in the 970s, the caliph al-Aziz confined them to Upper Egypt, where they lived by raiding. In Ifriqiya, meanwhile, the Zirid emir al-Mu'izz ibn Badis, pressed by the Sunni jurists of Kairouan and by anti-Shi'ite riots, broke with his Fatimid overlords, recognised the Abbasid caliph and denounced the Fatimids as heretics on his coins; the sources date the break variously between 1041 and 1051. In reply the caliph, on the advice of his vizier al-Yazuri, gave the Maghreb to the Banu Hilal and the Banu Sulaym; the Fatimids gave each Bedouin tribesman a camel and money and helped the tribes across the Nile, while a severe drought in Egypt also pushed them west. The caliph is reported to have told them: "I have given you the Maghrib and the rule of al-Mu'izz ibn Balkin as-Sanhaji, the runaway slave".

The nomads laid waste Cyrenaica in 1050 and left it to the Banu Sulaym, while the Banu Hilal moved on into Ifriqiya. On 14 April 1052, at Jabal Haydaran in the south-east of present-day Tunisia, they defeated the much larger army of al-Mu'izz; the countryside was ravaged, and in 1057 the emir abandoned Kairouan for the coastal fortress of Mahdia, after which the Bedouin sacked the old capital. The Zirids and their kinsmen the Hammadids, who paid tribute to the Bedouin and by 1090 had moved their capital from the Qal'a of the Banu Hammad to Béjaïa on the coast, were confined to coastal strips, and the economy of Ifriqiya turned increasingly to the sea, to maritime trade and piracy.

Ibn Khaldun, writing in the 14th century, held that the lands ravaged by the Banu Hilal had turned into desert, and his verdict long shaped the image of the invasion as a catastrophe. Modern historians debate its scale: Ifriqiya was already in economic crisis in the 1040s, with currency devaluation, epidemic and famine, and Jean Poncet (1967) called the "Hilalian catastrophe" a myth, while Hady Roger Idris (1968) defended its reality. The long-term result is not in doubt: the Arab tribes spread nomadism and Bedouin Arabic through the countryside and steppes of the Maghreb, a major factor in its Arabization, and their migration is retold in the epic of the Banu Hilal.