Some historians estimate that between 11 and 18 million black African slaves crossed the Red Sea, Indian Ocean, and Sahara Desert from 650 AD to 1900 AD, or more than the 9.4 to 14 million Africans brought to the Americas in the Atlantic slave trade.
The medieval slave trade in Europe was mainly to the East and South: The Byzantine Empire and the Muslim World were the destinations, pagan Central and Eastern Europe an important source. Slavery in medieval Europe was so common that the Roman Catholic Church repeatedly prohibited it— or at least the export of Christian slaves to non-Christian lands was prohibited at, for example, the Council of Koblenz in 922, the Council of London in 1102, and the Council of Armagh in 1171. Viking, Arab, Greek and Jewish merchants (known as Radhanites) were all involved in the slave trade during the Early Middle Ages.
Periodic raiding expeditions were sent from Islamic Iberia to ravage the Christian Iberian kingdoms, bringing back booty and slaves. In a raid against Lisbon in 1189 CE, for example, the Almohad caliph Yaqub al-Mansur took 3,000 female and child captives, while his governor of Córdoba, in a subsequent attack upon Silves in 1191 CE, took 3,000 Christian slaves.
According to Robert Davis between 1 million and 1.25 million Europeans were captured by Barbary pirates, who were vassals of the Ottoman Empire, and sold as slaves between the 16th and 19th centuries. These slaves were captured mainly from seaside villages from Italy, Spain, Portugal and also from more distant places like France or England, the Netherlands, Ireland and even Iceland and North America. The impact of these attacks was devastating – France, England, and Spain each lost thousands of ships, and long stretches of the Spanish and Italian coasts were almost completely abandoned by their inhabitants. Pirate raids discouraged settlement along the coast until the 19th century.
The 'Oriental' or 'Arab' slave trade is sometimes called the 'Islamic' slave trade, but a religious imperative was not the driver of the slavery, Patrick Manning, a professor of World History, states. However, since if a non-Muslim population refuses to adopt Islam or pay the Jizzya protection/ subjugation tax, that population is considered to be at war with the Muslim "ummah" and therefore it becomes legal under Islamic law to take slaves from that non-Muslim population. Usage of the terms "Islamic trade" or "Islamic world" has been disputed by some Muslims as it treats Africa as outside of Islam, or a negligible portion of the Islamic world. Propagators of Islam in Africa often revealed a cautious attitude towards proselytizing because of its effect in reducing the potential reservoir of slaves.
Historians say the Arab slave trade began in the 7th century and lasted more than a millennium. Arab traders brought Africans across the Indian Ocean from present-day Kenya, Tanzania, Sudan, western Ethiopia and elsewhere in East Africa to present-day Iraq, Iran, Kuwait, Turkey and other parts of the Middle East and South Asia (mainly Pakistan and India). Unlike the trans-Atlantic slave trade to the New World, Arabs supplied African slaves to the Muslim world, which at its peak stretched over three continents from the Atlantic (Morocco, Spain) to India and eastern China.
Elikia M’bokolo, April 1998, Le Monde diplomatique. Quote:"The African continent was bled of its human resources via all possible routes. Across the Sahara, through the Red Sea, from the Indian Ocean ports and across the Atlantic. At least ten centuries of slavery for the benefit of the Muslim countries (from the ninth to the nineteenth)." He continues: "Four million slaves exported via the Red Sea, another four million through the Swahili ports of the Indian Ocean, perhaps as many as nine million along the trans-Saharan caravan route, and eleven to twenty million (depending on the author) across the Atlantic Ocean
The history of the slave trade has given rise to numerous debates amongst historians. For one thing, specialists are undecided on the number of Africans taken from their homes; this is difficult to resolve because of a lack of reliable statistics: there was no census system in medieval Africa. Archival material for the transatlantic trade in the 16th to 18th centuries may seem useful as a source, yet these record books were often falsified. Historians have to use imprecise narrative documents to make estimates which must be treated with caution: Luiz Felipe de Alencastro states that there were 8 million slaves taken from Africa between the 8th and 19th centuries along the Oriental and the Trans-Saharan routes. Olivier Pétré-Grenouilleau has put forward a figure of 17 million African people enslaved (in the same period and from the same area) on the basis of Ralph Austen's work. Paul Bairoch suggests a figure of 25 million African people subjected to the Arab slave trade, as against 11 million that arrived in the Americas from the transatlantic slave trade. Owen 'Alik Shahadah author of African Holocaust (audio documentary), puts the figure at 10 million and argues that the trade only boomed in the 18th century, prior to this the trade was "a trickle trade" and that exaggerated numbers have been claimed in order to de-emphasize the Transatlantic trade.
Another obstacle to a history of the Arab slave trade is the limitations of extant sources. There exist documents from non-African cultures, written by educated men in Arabic, but these only offer an incomplete and often condescending look at the phenomenon. For some years there has been a huge amount of effort going into historical research on Africa. Thanks to new methods and new perspectives, historians can interconnect contributions from archaeology, numismatics, anthropology, linguistics and demography to compensate for the inadequacy of the written record.
In Africa, slaves taken by African owners were often captured, either through raids or as a result of warfare, and frequently employed in manual labor by the captors. Some slaves were traded for goods or services to other African kingdoms.
The Arab slave trade from East Africa is one of the oldest slave trades, predating the European transatlantic slave trade by hundreds of years. Male slaves who were often made eunuchs were employed as servants, soldiers, or laborers by their owners, while female slaves, mostly from Africa, were long traded to the Middle Eastern countries and kingdoms by Arab and Oriental traders, some as concubines and others as servants. Arab, African, and Oriental traders were involved in the capture and transport of slaves northward across the Sahara desert and the Indian Ocean region into the Middle East, Persia, and the Indian subcontinent.
From approximately 650 CE until around 1900 CE the Arab slave trade continued in one form or another. The Moroccan Sultan Moulay Ismail "the Bloodthirsty" (1672-1727) raised a corps of 150,000 black slaves, called his Black Guard, who coerced the country into submission. Historical accounts and references to slave-owning nobility in Arabia, Yemen and elsewhere are frequent into the early 1920s. In 1953, sheikhs from Qatar attending the coronation of Queen Elizabeth II included slaves in their retinues, and they did so again on another visit five years later. As recently as the 1950s, the Saudi Arabia’s slave population was estimated at 450,000 — just 20% of the population. It is estimated that as many as 200,000 black Sudanese children and women had been taken into slavery in Sudan during the Second Sudanese Civil War. Slavery in Mauritania was legally abolished by laws passed in 1905, 1961, and 1981. It was finally criminalized in August 2007. It is estimated that up to 600,000 black Mauritanians, or 20% of the Mauritania’s population, are currently enslaved, many of them used as bonded labour. For some people, any mention of the slave-trading past of the Arab world is rejected as an attempt to minimise the transatlantic trade. Yet a slave trade in the Indian Ocean, Red Sea, and Mediterranean pre-dates the arrival of any significant number of Europeans on the African continent.
Descendants of the African slaves brought to the Middle East during the slave-trade still exist there today, and are aware of their African origins.
A brief review of the region and era in which the Oriental and trans-Saharan slave trade took place should be useful here. It is not a detailed study of the Arab world, nor of Africa, but an outline of key points which will help with understanding the slave trade in this part of the world.
The framework of Islamic civilisation was a well-developed network of towns and oasis trading centres with the market (souk, bazaar) at its heart. These towns were inter-connected by a system of roads crossing semi-arid regions or deserts. The routes were travelled by convoys, and black slaves formed part of this caravan traffic.
His critical attitude towards Arabs has led the scholar Mohammad A. Enan to suggest that Ibn Khaldun may have been a Berber pretending to be an Arab in order to gain social status, but Muhammad Hozien has responded to this claim stating that Ibn Khaldun or anyone else in his family never claimed to be Berber even when the Berbers were in power.
In the same period, the Egyptian historian Al-Abshibi (1388-1446) wrote, "It is said that when the [black] slave is sated, he fornicates, when he is hungry, he steals.
In the 8th century AD, Africa was dominated by Arab-Berbers in the north: Islam moved southwards along the Nile and along the desert trails.
The Solomonic dynasty of Ethiopia often exported Nilotic slaves from their western borderland provinces, or from newly conquered or reconquered Muslim provinces. Native Muslim Ethiopian sultanates exported slaves as well, such as the sometimes independent Adal Sultanate. On the coast of the Indian Ocean too, slave-trading posts were set up by Arabs. The archipelago of Zanzibar, along the coast of present-day Tanzania, is undoubtedly the most notorious example of these trading colonies. East Africa and the Indian Ocean continued as an important region for the Oriental slave trade up until the 19th century. Livingstone and Stanley were then the first Europeans to penetrate to the interior of the Congo basin and to discover the scale of slavery there. The Arab Tippu Tip extended his influence and made many people slaves. After Europeans had settled in the Gulf of Guinea, the trans-Saharan slave trade became less important. In Zanzibar, slavery was abolished late, in 1897, under Sultan Hamoud bin Mohammed.
People were captured, transported, bought and sold by some very different characters. The trade passed through a series of intermediaries and enriched some sections of the Muslim aristocracy.
Slavery fed on wars between African peoples and states, which gave rise to an internal slave trade. Those conquered owed tribute in the form of men and women reduced to captivity. Sonni Ali Ber (1464–1492), emperor of Songhai, waged many wars to extend his territory.
In the 8th and 9th centuries, the Caliphs had tried to colonise the African shores of the Indian Ocean for commercial purposes. But these establishments were ephemeral, often founded by exiles or adventurers. The Sultan of Cairo sent slave traffickers on raids against the villages of Darfur. In the face of these attacks, the people formed militias, building towers and outer defences to protect their villages.
Merchants of slaves for the Orient stocked up in Europe. Danish merchants had bases in the Volga region and dealt in Slavs with Arab merchants. Circassian slaves were conspicuously present in the harems and there were many odalisques from that region in the paintings of Orientalists. Non-Muslim slaves were valued in the harems, for all roles (gate-keeper, servant, odalisque, musician, dancer, court dwarf). In the Ottoman Empire, the last black slave sold in Ethiopia named Hayrettin Effendi, was freed in 1918. The slaves of Slavic origin in Al-Andalus came from the Varangians who had captured them. They were put in the Caliph's guard and gradually took up important posts in the army (they became saqaliba), and even went to take back taifas after the civil war had led to an implosion of the Western Caliphate. Columns of slaves feeding the great harems of Cordoba, Seville and Grenada were organised by Jewish merchants (mercaderes) from Germanic countries and parts of Northern Europe not controlled by the Carolingian Empire. These columns crossed the Rhône valley to reach the lands to the south of the Pyrenees.
There are also many historical evidence and reports of North African Muslim slave raids all along the Mediterranean coasts across Christian Europe and beyond to even as far north as the British Isles and Iceland. See book titled White Gold
Slaves were also brought into the Arab world via Central Asia. many of these slaves went on to serve in the armies forming an elite rank.
Historians know less about the sea routes. From the evidence of illustrated documents, and travellers' tales, it seems that people travelled on dhows or jalbas, Arab ships which were used as transport in the Red Sea. Crossing the Indian Ocean required better organisation and more resources than overland transport. Ships coming from Zanzibar made stops on Socotra or at Aden before heading to the Persian Gulf or to India. Slaves were sold as far away as India, or even China: there was a colony of Arab merchants in Canton. Serge Bilé cites a 12th century text which tells us that most well-to-do families in Canton had black slaves whom they regarded as savages and demons because of their physical appearance. Although Chinese slave traders bought slaves (Seng Chi i.e. the Zanj) from Arab intermediaries and "stocked up" directly in coastal areas of present-day Somalia, the local Somalis -- referred to as Baribah and Barbaroi (Berbers) by medieval Arab and ancient Greek geographers, respectively (see Periplus of the Erythraean Sea),and no strangers to capturing, owning and trading slaves themselves -- were not among them:
One important commodity being transported by the Arab dhows to Somalia was slaves from other parts of East Africa. During the nineteenth century, the East African slave trade grew enormously due to demands by Arabs, Portuguese, and French. Slave traders and raiders moved throughout eastern and central Africa to meet the rising demand for enslaved men, women, and children. Somalia did not supply slaves -- as part of the Islamic world Somalis were at least nominally protected by the religious tenet that free Muslims cannot be enslaved -- but Arab dhows loaded with human cargo continually visited Somali ports.
Slave labor in East Africa was drawn exclusively from the Zanj, who were Negroid Bantu-speaking peoples that lived along the East African coast in an area roughly comprising modern-day Tanzania, Mozambique and Malawi. The Zanj were for centuries shipped as slaves by Arab traders to all the countries bordering the Indian Ocean. The Umayyad and Abbasid caliphs recruited many Zanj slaves as soldiers and, as early as 696 AD, we learn of slave revolts of the Zanj against their Arab enslavers in Iraq (see Zanj Rebellion). Ancient Chinese texts also mention ambassadors from Java presenting the Chinese emperor with two Seng Chi (Zanj) slaves as gifts, and Seng Chi slaves reaching China from the Hindu kingdom of Sri Vijaya in Java.