Rustamid imamate at Tahert

Ibadi missionaries from Basra had won over many Berber tribes of Tripolitania by 740. Abd al-Rahman ibn Rustam, raised in Kairouan, was one of the ‘bearers of knowledge’, a group of Maghribi students taught in secret in Basra by the Ibadi scholar Abu Ubayda Muslim. After their return an Ibadi imamate was proclaimed in Tripolitania under Abu al-Khattab, which took Kairouan in 758; Ibn Rustam governed the city until August 761, when an Abbasid army under Muhammad ibn al-Ash'ath retook it and Abu al-Khattab was killed. Ibn Rustam fled west and founded Tahert near an old Roman town, and Ibadi refugees from Ifriqiya and the Jabal Nafusa settled around it.

After failed attempts to regain Kairouan, the Ibadis of the Maghreb elected Ibn Rustam imam in 776 or 778 (777 in some modern works). Ibadi tradition says that he was chosen because, as a foreigner, he belonged to no tribe and would favour none, and that he made his electors swear to obey his just orders. The office nevertheless became hereditary: his son Abd al-Wahhab succeeded him, and the community split over the succession. At its height in the early 9th century the imamate controlled much of the central Maghreb as far as Tlemcen, and its imams were recognised by Ibadis as far as the Jabal Nafusa.

Tahert, nicknamed ‘the Iraq of the Maghreb’ and ‘Little Basra’, was a walled religious and commercial centre on the caravan routes, where Christians and non-Ibadi Muslims also lived; Ibadi merchants from the Maghreb travelled as far as Gao and Ghana, spreading Islam as they traded. The Rustamids kept good relations with Sijilmasa and with the Umayyads of Córdoba but were attacked by the Idrisids. In 909 the Fatimid general Abu Abd Allah al-Shi'i took Tahert; the surviving Ibadis withdrew to Ouargla and later to the Mzab.