The jihad proclaimed by Usman dan Fodio in 1804 overthrew the Hausa city-states and created the Sokoto Caliphate, which by the 1830s governed a population estimated in the millions across some thirty emirates. Warfare with non-Muslim polities on its southern and eastern frontiers - in the Middle Belt, Adamawa and around Lake Chad - was a continuing source of captives, since Islamic law as applied in the caliphate permitted enslavement of non-Muslims taken in jihad; captives were settled on plantations producing grain, cotton and indigo for the caliphate's cities, and were also sold into the trans-Saharan trade. Historians including Paul Lovejoy and Jan Hogendorn estimate the enslaved population at one to two and a half million by 1900, a share of total population comparable to the American South before abolition. Frontier populations fled to hill refuges and defensible sites, a settlement pattern colonial officials later recorded across the Jos plateau and the Middle Belt. Britain conquered the caliphate in 1900-1903 and abolished the legal status of slavery gradually, in a way designed to avoid disrupting the emirate economy, with slavery persisting in practice well into the twentieth century.
The Sokoto Caliphate conquered the Hausa states and raided the non-Muslim Middle Belt for captives held as agricultural slaves
The caliphate is usually estimated at 10-20 million people by 1837, the most populous state in West Africa; the figures derive from nineteenth-century European travellers' accounts, later colonial enumeration and modern reconstruction rather than any census. Hogendorn and Lovejoy estimate that enslaved people made up between a quarter and a half of that population, with at least one million and perhaps 2.5 million held in slavery by 1900 — proportionally comparable to the American South.
No defensible range. Slave raiding, the wars of the jihad and the caravan routes north all caused substantial mortality, described in Arabic chronicles and by nineteenth-century European travellers such as Heinrich Barth, but no figures exist.
Arabic chronicles of the caliphate, nineteenth-century European travellers including Heinrich Barth, and British colonial slavery assessments documented captive-taking including of children, plantation labour and concubinage.
Nigeria