The Sudanic savanna is that vast belt of flat grasslands across Africa below the Sahara’s southern fringe (the Sahel), stretching from Senegal and Gambia in the west to the mountains of Ethiopia in the east. By the early eighteenth century Islam had been practiced throughout this region for five hundred to one thousand years, depending on the area. City dwellers, political rulers, and merchants in many small states were Muslim. Yet the rural peasant farmers and migratory cattle raisers — the vast majority of the population — generally held on to traditional animist practices, worshipping ancestors, praying at local shrines, and invoking protective spirits. Since many Muslim rulers shared some of these beliefs, they did not try to convert their subjects in the countryside or enforce Islamic law.

A powerful Islamic revival began in the eighteenth century and gathered strength in the early nineteenth century. This revival brought reform and revolutionary change from within to the western and eastern Sudan, until this process was halted by European military conquest at the end of the nineteenth century. In essence, Muslim scholars and fervent religious leaders arose to wage successful jihads, or religious wars, against both animist rulers and Islamic states they deemed corrupt. The new reformist rulers believed African cults and religious practice could no longer be tolerated, and they often effected mass conversions of animists to Islam.

The most important of these revivalist states, the mighty Sokoto caliphate, illustrates the pattern of Islamic revival in Africa. It was founded by Uthman dan Fodio (1754–1817), an inspiring Muslim teacher who first won followers among both the Fulani herders and the Hausa peasants in the Muslim state of Gobir in the northern Sudan. After his religious community was attacked by Gobir’s rulers, Uthman launched the jihad of 1804, one of the most important events in nineteenth-century West Africa. Uthman claimed the Hausa rulers of Muslim Gobir “worshipped many places of idols, and trees, and rocks, and sacrificed to them,” killing and plundering their subjects without any regard for Islamic law.3 He recruited young religious students and discontented Fulani cattle raisers to form the backbone of his jihadi fighters and succeeded in overthrowing the Hausa rulers and expanding Islam into the Sudan. In 1809 Uthman established the new Sokoto caliphate, which was ably consolidated by his son Muhammad Bello as a vast and enduring decentralized state.

The triumph of the Sokoto caliphate had profound consequences for Africa and the Sudan. First, the caliphate was governed by a sophisticated written constitution based on Islamic history and law, something earlier sub-Saharan African preliterate states had never achieved. This government of laws, rather than men, provided stability and made Sokoto one of the most prosperous regions in tropical Africa. Second, because of Sokoto and other revivalist states, Islam became much more widely and deeply rooted in sub-Saharan Africa than ever before. By 1880 Islam united the entire western and central Sudan and had become an unquestioned part of everyday life and culture. Women gained greater access to education, even as veiling and seclusion became more common. Finally, as one historian explained, Islam had always approved of slavery for non-Muslims and Muslim heretics, and “the jihads created a new slaving frontier on the basis of rejuvenated Islam.”4 In 1900 the Sokoto caliphate had at least 1 million and perhaps as many as 2.5 million slaves. Among all modern slave societies, only the American South had more slaves, about 4 million in 1860.

Islam also expanded in East Africa. From the 1820s on, Arab merchants and adventurers pressed far into the interior in search of slaves and ivory, converting and intermarrying with local Nyamwezi (nyahm-WAY-zee) elites and establishing small Muslim states. The Arab immigrants brought literacy, administrative skills, and increased trade and international contact, as well as the intensification of slavery, to East Africa. In 1837 Sayyid Said (r. 1804–1856), the energetic sultan of Oman, conquered Mombasa, the great port city in modern Kenya. After reviving his family’s lordship of the African island of Zanzibar, he moved his capital from southern Arabia to Zanzibar in 1840. Sayyid Said (sa-EED sa-EED) and his Baluchi mercenaries (from present-day Pakistan) then gained control of most of the Swahili-speaking East African coast. This allowed him to route all slave shipments from the coast to the Ottoman Empire and Arabia through Zanzibar. In addition, he successfully encouraged Indian merchants to develop slave-based clove plantations in his territories. In 1870, before Christian missionaries and Western armies began to arrive in force and halt Islam’s spread, it appeared that most of the East and Central African populations would accept Islam within a generation.5