By 1147, 17 years after Ibn Tūmart’s death, Almohads had replaced Almoravids in all their Maghribi and Andalusian territories. In Andalusia their arrival slowed the progress of the Christian Reconquista. There, as in the Maghrib, arts and letters were encouraged; an example is an important movement of falsafah that included Ibn Ṭufayl, Ibn al-ʿArabī, and Ibn Rushd (Latin Averroës), the Andalusian qāḍī and physician whose interpretations of Aristotle became so important for medieval European Christianity. During the late Almohad period in Andalusia the intercommunal nature of Islamicate civilization became especially noticeable in the work of non-Muslim thinkers, such as Moses Maimonides, who participated in trends outside their own communities even at the expense of criticism from within. By the early 13th century, Almohad power began to decline; a defeat in 1212 at Las Navas de Tolosa by the Christian kings of the north forced a retreat to the Maghrib. But the impact of Almohad cultural patronage on Andalusia long outlasted Almohad political power; successor dynasties in surviving Muslim states were responsible for some of the highest cultural achievements of Andalusian Muslims, among them the Alhambra palace in Granada. Furthermore, the 400-year southward movement of the Christian-Muslim frontier resulted, ironically, in some of the most intense Christian-Muslim interaction in Andalusian history. The Cid could fight for both sides; Muslims, as Mudejars, could live under Christian rule and contribute to its culture; Jews could translate Arabic and Hebrew texts into Castilian. Almohads were replaced in the Maghrib as well, through a revolt by their own governors—the Ḥafṣids in Tunis and the Marīnid Amazigh dynasty in Fès. There too, however, Almohad influence outlasted their political presence: both towns became centres, in distinctively Maghribi form, of Islamicate culture and Islamic piety.

Continued spread of Islamic influence

As the Maghrib became firmly and distinctively Muslim, Islam moved south. The spread of Muslim identity into the Sahara and the involvement of Muslim peoples, especially the Tuareg, in trans-Saharan trade provided several natural channels of influence. By the time of the Marīnids, Ḥafṣids, and Mamlūks, several major trade routes had established crisscrossing lines of communication: from Cairo to Timbuktu, from Tripoli to Bornu and Lake Chad, from Tunis to Timbuktu at the bend of the Niger River, and from Fès and Tafilalt through major Saharan entrepôts into Ghana and Mali. The rise at Timbuktu of Mali, the first great western Sudanic empire with a Muslim ruler, attested the growing incorporation of sub-Saharan Africa into the North African orbit. The reign of Mansa Mūsā, who even went on pilgrimage, demonstrated the influence of Islam on at least the upper echelons of African society.

The best picture of Islamdom in the 14th century appears in the work of a remarkable Maghribi qāḍī and traveler, Ibn Baṭṭūṭah (1304–1368/69 or 1377). In 1325, the year that Mansa Mūsā went on pilgrimage, Ibn Baṭṭūṭah also left for Mecca, from his hometown of Tangiers. He was away for almost 30 years, visiting most of Islamdom, including Andalusia, all of the Maghrib, Mali, Syria, Arabia, Iran, India, the Maldive Islands, and, he claimed, China. He described the unity within diversity that was one of Islamdom’s most prominent features. Although local customs often seemed at variance with his notion of pure Islamic practice, he felt at home everywhere. Despite the divisions that had occurred during Islam’s 700-year history, a Muslim could attend the Friday worship session in any Muslim town in the world and feel comfortable, a claim that is difficult if not impossible to make for any other major religious tradition at any time in its history. By the time of Ibn Baṭṭūṭah’s death, Islamdom comprised the most far-flung yet interconnected set of societies in the world. As one author has pointed out, Thomas Aquinas (c. 1224–74) might have been read from Spain to Hungary and from Sicily to Norway, but Ibn al-ʿArabī (1165–1240) was read from Spain to Sumatra and from the Swahili coast to Kazan on the Volga River. By the end of the period of migration and renewal, Islam had begun to spread not only into sub-Saharan Africa but also into the southern seas with the establishment of a Muslim presence in the Straits of Malacca. Conversion to Islam across its newer frontiers was at first limited to a small elite, who supplemented local religious practices with Muslim ones. Islam could offer not only a unifying religious system but also social techniques, including alphabetic literacy, a legal system applicable to daily life, a set of administrative institutions, and a body of science and technology—all capable of enhancing the power of ruling elements and of tying them into a vast and lucrative trading network.

The period of migration and renewal exposed both the potentiality and the limitations of government by tribal peoples. This great problem of Islamicate history received its most sophisticated analysis from a Maghribi Muslim named Ibn Khaldūn (1332–1406), a contemporary of Petrarch. His family had migrated from Andalusia to the Maghrib, and he himself was born in Ḥafṣid territory. He was both a faylasūf and a qāḍī, a combination more common in Andalusia and the Maghrib than anywhere else in Islamdom. His falsafah was activist; he strove to use his political wisdom to the benefit of one of the actual rulers of the day. To this end he moved from one court to another before becoming disillusioned and retiring to Mamlūk Cairo as a qāḍī. His life thus demonstrated the importance and the constraints of royal patronage as a stimulant to intellectual creativity. In his Muqaddimah (the introduction to his multivolume world history) he used his training in falsafah to discern patterns in history. Transcending the critiques of historical method made by historians of the Būyid period, such as al-Masʿūdī, Ibn Miskawayh, and al-Ṣūlī, Ibn Khaldūn established careful standards of evidence. Whereas Muslim historians conventionally subscribed to the view that God passed sovereignty and hegemony (dawlah) from one dynasty to another through his divine wisdom, Ibn Khaldūn explained it in terms of a cycle of natural and inevitable stages. By his day it had become apparent that tribally organized migratory peoples, so favoured by much of the ecology of the Maghrib and the Nile-to-Oxus region, could easily acquire military superiority over settled peoples if they could capitalize on the inherently stronger group feeling (ʿaṣabiyyah) that kinship provides. Once in power, according to Ibn Khaldūn, conquering groups pass through a phase in which a small number of “builders” among them bring renewed vitality to their conquered lands. As the family disperses itself among sedentary peoples and ceases to live the hard life of migration, it becomes soft from the prosperity it has brought and begins to degenerate. Then internal rivalries and jealousies force one member of the family to become a king who must rely on mercenary troops and undermine his own prosperity by paying for them. In the end, the ruling dynasty falls prey to a new tribal group with fresh group feeling. Thus did Ibn Khaldūn call attention to the unavoidable instability of all premodern Muslim dynasties, caused by their lack of the regularized patterns of succession that were beginning to develop in European dynasties.