African slaves became part of the Atlantic slave trade, from which comes the modern, Western conception of slavery as an institution of African-descended slaves and non-African slave owners. Despite its illegality, slavery continues in some parts of the world, including Africa.
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"
In most African societies, there was very little difference between the free peasants and the feudal vassal peasants. Slaves of the Songhai Empire were used primarily in agriculture; they paid tribute to their masters in crop and service but they were slightly restricted in custom and convenience. These non-free people were more an occupational caste, as their bondage was relative..
There is adequate evidence citing case after case of African control of segments of the trade. Several African nations such as the Ashanti of Ghana and the Yoruba of Nigeria had economies largely depending on the trade. African peoples such as the Imbangala of Angola and the Nyamwezi of Tanzania would serve as intermediaries or roving bands of war with other African nations to capture Africans for export as slaves out of Africa. Extenuating circumstances demanding exploration are the efforts European and Arab officials in Africa used to install rulers agreeable to their interests. They would actively favor one African group against another to deliberately ignite chaos and continue their slaving activities..
"Slavery", as it is often referred to by people, in African cultures was generally more like indentured servitude: "slaves" were not made to be chattel of other men, nor enslaved for life. African "slaves" were paid wages and were able to accumulate property. They often bought their own freedom and could then achieve social promotion -just as freedman in ancient Rome- some even rose to the status of kings (e.g. Jaja of Opobo and Sunni Ali Ber). Similar arguments were used by Western slave owners during the time of abolition, for example by John Wedderburn in Wedderburn v. Knight, the case that ended legal recognition of slavery in Scotland in 1776. Regardless of the legal options open to slave owners, rational cost-earning calculation and/or voluntary adoption of moral restraints often tended to mitigate (except with traders, who preferred to weed out the worthless weak individuals) the actual fate of slaves throughout history.
In Senegambia, between 1300 and 1900, close to one-third of the population was enslaved. In early Islamic states of the western Sudan, including Ghana (750–1076), Mali (1235–1645), Segou (1712–1861), and Songhai (1275–1591), about a third of the population were slaves. In Sierra Leone in the 19th century about half of the population consisted of slaves. In the 19th century at least half the population was enslaved among the Duala of the Cameroon, the Igbo and other peoples of the lower Niger, the Kongo, and the Kasanje kingdom and Chokwe of Angola. Among the Ashanti and Yoruba a third of the population consisted of slaves. The population of the Kanem (1600–1800) was about a third-slave. It was perhaps 40% in Bornu (1580–1890). Between 1750 and 1900 from one- to two-thirds of the entire population of the Fulani jihad states consisted of slaves. The population of the Sokoto caliphate formed by Hausas in the northern Nigeria and Cameroon was half-slave in the 19th century. Between 65% to 90% of the population of Arab–Swahili Zanzibar was enslaved. Roughly half the population of Madagascar was enslaved.
When British rule was first imposed on the Sokoto Caliphate and the surrounding areas in northern Nigeria at the turn of the 20th century, approximately 2 million to 2.5 million people there were slaves. Slavery in northern Nigeria was finally outlawed in 1936.
Slavery as practiced in what is modern Ethiopia and Eritrea was essentially domestic. Slaves thus served in the houses of their masters or mistresses, and were not employed to any significant extent for productive purpose. Slaves were thus regarded as second-class members of their owners' family, and were fed, clothed and protected. Women were taken as sex slaves. They generally roamed around freely and conducted business as free people. They had complete freedom of religion and culture. The first attempt to abolish slavery in Ethiopia was made by Emperor Tewodros II (r. 1855–1868), although the slave trade was not abolished completely until 1923 with Ethiopia's ascension to the League of Nations. Anti-Slavery Society estimated there were 2,000,000 slaves in the early 1930s out of an estimated population of between 8 and 16 million. Slavery continued in Ethiopia until the Italian invasion in October 1935, when the institution was abolished by order of the Italian occupying forces. In response to pressure by Western Allies of World War II, Ethiopia officially abolished slavery and involuntary servitude after having regained its independence in 1942. On August 26, 1942 Haile Selassie issued a proclamation outlawing slavery.
The Bantus are the descendants of people from various ethnic groups in what is modern-day Tanzania, Malawi and Mozambique who were brought to Somalia as slaves in the 19th century. It is estimated that the Bantu in Somalia number around 80,000 (1970 estimate) out of a total population of over 11 million, with most concentrated between the Juba and Shabelle rivers in the south. Contrary to the Somalis, who are for the most part nomadic herders, the Bantu are mainly sedentary farmers. Bantus are also ethnically, physically, and culturally distinct from Somalis, and have remained marginalized ever since their arrival in Somalia. During the recent civil war in Somalia, many Bantu were evicted from their farms by various armed factions of Somali clans.
The medieval slave trade in Europe was mainly to the East and South: Byzantine Empire and the Muslim World were the destinations, 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. Because of religious constraints, the slave trade was monopolised in parts of Europe by Iberian Jews (known as Radhanites) who were able to transfer the slaves from pagan Central Europe through Christian Western Europe to Muslim countries in Al-Andalus and Africa. So many Slavs were enslaved for so many centuries that word 'Slav' became synonymous with slavery. The derivation of the word slave encapsulates a bit of European history and explains why the two words (slaves and Slavs) are so similar; they are, in fact, historically identical.
Mamluks were slave soldiers who converted to Islam and served the Muslim caliphs and the Ayyubid sultans during the Middle Ages. The first mamluks served the Abbasid caliphs in 9th century Baghdad. Over time they became a powerful military caste, and on more than one occasion they seized power for themselves, for example, ruling Egypt from 1250–1517. From 1250 Egypt had been ruled by the Bahri dynasty of Kipchak Turk origin. White slaves from the Caucasus served in the army and formed an elite corp of troops eventually revolting in Egypt to form the Burgi dynasty.
According to Robert Davis between 1 million and 1.25 million Europeans were captured by Barbary pirates and sold as slaves to North Africa and the Ottoman Empire between the 16th and 19th centuries. The coastal villages and towns of Italy, Portugal, Spain and Mediterranean islands were frequently attacked by them and long stretches of the Italian and Spanish coasts were almost completely abandoned by its inhabitants; after 1600 Barbary pirates occasionally entered the Atlantic and struck as far north as Iceland. The most famous corsairs were the Ottoman Barbarossa ("Redbeard"), and his older brother Oruç, Turgut Reis (known as Dragut in the West), Kurtoğlu (known as Curtogoli in the West), Kemal Reis, Salih Reis and Koca Murat Reis.
In 1544, Hayreddin Barbarossa captured the Ischia, taking 4,000 prisoners in the process, and deported to slavery some 9,000 inhabitants of Lipari, almost the entire population. In 1551, Dragut enslaved the entire population of the Maltese island Gozo, between 5,000 and 6,000, sending them to Libya. When pirates sacked Vieste in southern Italy in 1554 they took an 7,000 slaves. In 1555, Turgut Reis sailed to Corsica and ransacked Bastia, taking 6000 prisoners. In 1558 Barbary corsairs captured the town of Ciutadella, destroyed it, slaughtered the inhabitants and carried off 3,000 survivors to Istanbul as slaves. In 1563 Turgut Reis landed at the shores of the province of Granada, Spain, and captured the coastal settlements in the area like Almuñécar, along with 4,000 prisoners. Barbary pirates frequently attacked the Balearic islands, resulting in many coastal watchtowers and fortified churches being erected. The threat was so severe that Formentera became uninhabited.
Sahrawi-Moorish society in Northwest Africa was traditionally (and still is, to some extent) stratified into several tribal castes, with the Hassane warrior tribes ruling and extracting tribute – horma – from the subservient Berber-descended znaga tribes. The so-called Haratin lower class, largely sedentary oasis-dwelling black people>
The very earliest external slave trade was the trans-Saharan slave trade. Although there had long been some trading up the Nile River and very limited trading across the western desert, the transportation of large numbers of slaves did not become viable until camels were introduced from Arabia in the 10th century. By this point, a trans-Saharan trading network came into being to transport slaves north. Zanzibar was once East Africa's main slave-trading port, and under Omani Arabs in the 19th century as many as 50,000 slaves were passing through the city each year. Most 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, Frequent intermarriages meant that the slaves were assimilated in North Africa. Unlike in the Americas, slaves in North Africa were mainly servants and soldiers rather than labourers, and a greater number of females than males were taken, who were often employed as servants, forced into prostitution or to become the women of harems. It was also not uncommon to turn male slaves, both African and European, into eunuchs via castration to serve as guardians to the harems. 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. Slavery in Morocco was finally outlawed in the 1930s.
The trade of slaves across the Indian Ocean also has a long history beginning with the control of sea routes by Afro-Arab traders in the ninth century. It is estimated that only a few thousand slaves were taken each year from the Red Sea and Indian Ocean coast. They were sold throughout the Middle East. This trade accelerated as superior ships led to more trade and greater demand for labour on plantations in the region. Eventually, tens of thousands per year were being taken.. In east Africa the main slave trade involved arabized east Africans 
David Livingstone wrote of the slave trade: "To overdraw its evils is a simple impossibility ... We passed a slave woman shot or stabbed through the body and lying on the path. [Onlookers] said an Arab who passed early that morning had done it in anger at losing the price he had given for her, because she was unable to walk any longer. We passed a woman tied by the neck to a tree and dead ... We came upon a man dead from starvation ... The strangest disease I have seen in this country seems really to be broken heartedness, and it attacks free men who have been captured and made slaves." Livingstone estimated that 80,000 Africans died each year before ever reaching the slave markets of Zanzibar. Zanzibar was once East Africa's main slave-trading port, and under Omani Arabs in the 19th century as many as 50,000 slaves were passing through the city each year.
The first Europeans to arrive on the coast of Guinea were the Portuguese; the first European to actually buy African slaves in the region of Guinea was Antão Gonçalves, a Portuguese explorer. Originally interested in trading mainly for gold and spices, they set up colonies on the uninhabited islands of São Tomé. In the 16th century the Portuguese settlers found that these volcanic islands were ideal for growing sugar. Sugar growing is a labour-intensive undertaking and Portuguese settlers were difficult to attract due to the heat, lack of infrastructure, and hard life. To cultivate the sugar the Portuguese turned to large numbers of African slaves. Elmina Castle on the Gold Coast, originally built by African labor for the Portuguese in 1482 to control the gold trade, became an important depot for slaves that were to be transported to the New World.
The first Europeans to use African slaves in the New World were the Spaniards who sought auxiliaries for their conquest expeditions and labourers on islands such as Cuba and Hispaniola, where the alarming death rate in the native population had spurred the first royal laws protecting the native population (Laws of Burgos, 1512–1513). In general, however, the Spaniards were known for their continued harsh treatment of slaves until the ending of trade in the 1800s. The first African slaves arrived in Hispaniola in 1501.
In 1452, Pope Nicholas V issued the papal bull Dum Diversas, granting Afonso V of Portugal the right to reduce any "Saracens, pagans and any other unbelievers" to hereditary slavery. This approval of slavery was reaffirmed and extended in his Romanus Pontifex bull of 1455. These papal bulls came to serve as a justification for the subsequent era of slave trade and European colonialism. However Pope Eugene IV in his bull, Sicut Dudum of 1435 had condemned the enslavement of the black inhabitants of the Canary Islands. Pope Paul III in 1537 issued an additional Bull, Sublimis Deus, declaring that all peoples, even those outside the faith should not be deprived of their liberty. The followers of the church of England and Protestants did not use the papal bulls as a justification for their involvement in slavery.
Increasing penetration into the Americas by the Portuguese created more demand for labour in Brazil--primarily for farming and mining. Slave-based economies quickly spread to the Caribbean and the southern portion of what is today the United States, where Dutch traders brought the first African slaves in 1619. These areas all developed an insatiable demand for slaves. As European nations grew more powerful, especially Portugal, Spain, France, Great Britain and the Netherlands, they began vying for control of the African slave trade, with little effect on the local African and Arab trading. Great Britain's existing colonies in the Lesser Antilles and their effective naval control of the Mid Atlantic forced other countries to abandon their enterprises due to inefficiency in cost. The English crown provided a charter giving the Royal African Company monopoly over the African slave routes until 1712.
The Atlantic slave trade peaked in the late 18th century, when the largest number of slaves were captured on raiding expeditions into the interior of West Africa. These expeditions were typically carried out by African kingdoms against weaker African tribes and peoples. These mass slavers included the Oyo empire (Yoruba), Kong Empire, Kingdom of Benin, Kingdom of Fouta Djallon, Kingdom of Fouta Tooro, Kingdom of Koya, Kingdom of Khasso, Kingdom of Kaabu, Fante Confederacy, Ashanti Confederacy, and the kingdom of Dahomey. Europeans rarely entered the interior of Africa, due to fear of disease and moreover fierce African resistance.
Before the arrival of the Portuguese, slavery had already existed in Kingdom of Kongo. Despite its establishment within his kingdom, Afonso I of Kongo believed that the slave trade should be subject to Kongo law. When he suspected the Portuguese of receiving illegally enslaved persons to sell, he wrote letters to the King João III of Portugal in 1526 imploring him to put a stop to the practice.
The kings of Dahomey sold their war captives into transatlantic slavery, who otherwise would have been killed in a ceremony known as the Annual Customs. As one of West Africa's principal slave states, Dahomey became extremely unpopular with neighbouring peoples. Like the Bambara Empire to the east, the Khasso kingdoms depended heavily on the slave trade for their economy. A family's status was indicated by the number of slaves it owned, leading to wars for the sole purpose of taking more captives. This trade led the Khasso into increasing contact with the European settlements of the west coast, particularly the French. Benin grew increasingly rich during the 16th and 17th centuries on the slave trade with Europe; slaves from enemy states of the interior were sold, and carried to the Americas in Dutch and Portuguese ships. The Bight of Benin's shore soon came to be known as the "Slave Coast".
Several historians, such as João C. Curto, have made important contributions to the global understanding of the African side of the Atlantic slave trade. By arguing that African merchants determined the assemblage of trade goods accepted in exchange for slaves, many historians argue for African agency and ultimately a shared responsibility for the slave trade.
King Gezo of Dahomey said in 1840s:
In 1807, the UK Parliament passed the Bill that abolished the trading of slaves. The King of Bonny (now in Nigeria) was horrified at the conclusion of the practice:
The slaves came from many different sources. About half came from the societies that sold them. These might be criminals, heretics, the mentally ill, the indebted and any others that had fallen out of favour with the rulers. Little is known about the details of these practices before the arrival of Europeans, and so it is difficult to tell if the number of people considered as undesirables was artificially increased to provide more slaves for export. It is believed that capital punishment in the region nearly disappeared since prisoners became far too valuable to dispose of in such a way.
Another source of slaves, comprising about half the total, came from military conquests of other states or tribes. It has long been contended that the slave trade greatly increased violence and warfare in the region due to the pursuit of slaves, endemic warfare was certainly common even before slave hunting had added such an extra inducement.
For the Atlantic slave trade, captives purchased from slave dealers in West African regions known as the Slave Coast, Gold Coast, and Côte d'Ivoire were sold into slavery as a result of a defeat in warfare. In the Bight of Biafra near modern-day Senegal and Benin, some African kings sold their captives locally and later to European slave traders for goods such as metal cookware, rum, livestock, and seed grain. Previous to the voyage, the victims were held in "slave castles" and deep pits where many died from multiple illnesses and malnutrition. Conditions were even worse in the Middle Passage across the Atlantic where up to a third of the slaves died en route.
Most scholars find that the trade in slaves had a detrimental effect on long-term economic growth and development. It ultimately undermined local economies and political stability as villages' vital labor forces were shipped overseas as slave raids and civil wars became commonplace. With the rise of a large commercial slave trade, driven by European needs, enslaving your enemy became less a consequence of war, and more and more a reason to go to war. The slave trade impeded the formation of larger ethnic groups, causing ethnic fractionalisation and weakening the formation for stable political structures. It also reduced the mental health and social development of African people and created a situation where 
In contrast, J.D. Fage asserts that slavery did not have a wholly disastrous effect on those left behind in Africa. Slaves were an expensive commodity, and traders received a great deal in exchange for each slave. At the peak of the slave trade, it is said that hundreds of thousands of muskets, vast quantities of cloth, gunpowder, and metals were being shipped to Guinea. Most of this money was spent on British-made firearms (of very poor quality) and industrial-grade alcohol. Trade with Europe at the peak of the slave trade—which also included significant exports of gold and ivory—was some 3.5 million pounds Sterling per year. By contrast, the trade of the United Kingdom, the economic superpower of the time, was about 14 million pounds per year over this same period of the late 18th century. As Patrick Manning has pointed out, the vast majority of items traded for slaves were common rather than luxury goods. Textiles, iron ore, currency, and salt were some of the most important commodities imported as a result of the slave trade, and these goods were spread within the entire society raising the general standard of living.
Eric Williams had attempted to show the contribution of Africans on the basis of profits from the slave trade and slavery, and the employment of those profits to finance Britain’s industrialization process. He argues that the enslavement of Africans was an essential element to the Industrial Revolution, and that European wealth is a result of slavery. However, he argued that by the time of its abolition it had lost its profitability and it was in Britain's economic interest to ban it. Seymour Dreshcer and Robert Antsey have both presented evidence that the slave trade remained profitable until the end, and that reasons other than economics led to its cessation. Joseph Inikori has shown elsewhere that the British slave trade was more profitable than the critics of Williams would want us to believe. Nevertheless, the profits of the slave trade and of West Indian plantations amounted to less than 5% of the British economy at the time of the Industrial Revolution.
A similar debate has taken place about other European nations. French slave trade was more profitable than alternative domestic investments and probably encouraged capital accumulation before the Industrial Revolution and Napoleonic Wars.
The demographic effects of the slave trade are some of the most controversial and debated issues. Tens of millions of people were removed from Africa via the slave trade, and what effect this had on Africa is an important question. Walter Rodney argued that the export of so many people had been a demographic disaster and had left Africa permanently disadvantaged when compared to other parts of the world, and largely explains that continent's continued poverty. He presents numbers that show that Africa's population stagnated during this period, while that of Europe and Asia grew dramatically. According to Rodney all other areas of the economy were disrupted by the slave trade as the top merchants abandoned traditional industries to pursue slaving and the lower levels of the population were disrupted by the slaving itself.
Others have challenged this view. J. D. Fage compared the number effect on the continent as a whole. David Eltis has compared the numbers to the rate of emigration from Europe during this period. In the nineteenth century alone over 50 million people left Europe for the Americas, a far higher rate than were ever taken from Africa.
Others have challenged this view. Joseph E. Inikori argues the history of the region shows that the effects were still quite deleterious. He argues that the African economic model of the period was very different from the European, and could not sustain such population losses. Population reductions in certain areas also led to widespread problems. Inikori also notes that after the suppression of the slave trade Africa's population almost immediately began to rapidly increase, even prior to the introduction of modern medicines. Shahadah also states that the trade was not only of demographic significance, in aggregate population losses but also in the profound changes to settlement patterns, epidemiological exposure and reproductive and social development potential.
In addition, the majority of the slaves being taken to the Americas were male. So while the slave trade created an immediate drop in the population, its long term effects were less drastic..
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. " 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"
Maulana Karenga states that the effects of the African slave trade were "the morally monstrous destruction of human possibility involved redefining African humanity to the world, poisoning past, present and future relations with others who only know us through this stereotyping and thus damaging the truly human relations among people of today". He cites that it constituted the destruction of culture, language, religion and human possibility. It's worth noting though that slavery was and is a crime of opportunity, not just racism. Those who were enslaved were vulnerable to a more powerful people, and their vulnerability was their liability, not just their race.
Beginning in the late 18th century, France was Europe's first country to abolish slavery, in 1794, but it was revived by Napoleon in 1802, and banned for good in 1848. In 1807 the British Parliament passed the Abolition of the Slave Trade Act, under which captains of slave ships could be stiffly fined for each slave transported. This was later superseded by the 1833 Slavery Abolition Act, which freed all slaves in the British Empire. Abolition was then extended to the rest of Europe. The 1820 U.S. Law on Slave Trade made slave trading piracy, punishable by death. In 1827, Britain declares the slave trade piracy, punishable by death. The power of the Royal Navy was subsequently used to suppress the slave trade, and while some illegal trade, mostly with Brazil, continued, the Atlantic slave trade would be eradicated by the middle of the 19th century. The West Africa Squadron was credited with capturing 1,600 slave ships between 1808 and 1860 and freeing 150,000 Africans who were aboard these ships. Action was also taken against African leaders who refused to agree to British treaties to outlaw the trade, for example against ‘the usurping King of Lagos’, deposed in 1851. Anti-slavery treaties were signed with over 50 African rulers.
The Islamic trans-Saharan and Indian Ocean trades continued, however, and even increased as new sources of slaves became available. In Caucasus, slavery was abolished after Russian conquest. The slave trade within Africa also increased. The British Navy could suppress much of the trade in the Indian Ocean, but the European powers could do little to affect the intra-continental trade.
The continuing anti-slavery movement in Europe became an excuse and a casus belli for the European conquest and colonisation of much of the African continent. In the late 19th century, the Scramble for Africa saw the continent rapidly divided between Imperialistic Europeans, and an early but secondary focus of all colonial regimes was the suppression of slavery and the slave trade. In response to this public pressure, Ethiopia officially abolished slavery in 1932. By the end of the colonial period they were mostly successful in this aim, though slavery is still very active in Africa even though it has gradually moved to a wage economy. Independent nations attempting to westernise or impress Europe sometimes cultivated an image of slavery suppression, even as they, in the case of Egypt, hired European soldiers like Samuel White Baker's expedition up the Nile. Slavery has never been eradicated in Africa, and it commonly appears in African states, such as Chad, Ethiopia, Mali, Niger, and Sudan, in places where law and order have collapsed. See also Slavery in modern Africa.
Although outlawed in nearly all countries today slavery is practiced in secret in many parts of the world. There are an estimated 27 million victims of slavery worldwide. In Mauritania alone up to 600,000 men, women and children, or 20% of the population, are enslaved, many of them used as bonded labour. Slavery in Mauritania was finally criminalized in August 2007. It is estimated that as many as 200,000 black Sudanese children and women have been taken into slavery in Sudan during the Second Sudanese Civil War. In Niger, where the practice of slavery was outlawed in 2003, a study found that almost 8% of the population are still slaves.
The African slave trade was a trade in slaves, and, like most of the world, has carried on for thousands of years in Africa. The first main route passed through the Sahara. After the Age of Exploration, African slaves became part of the Atlantic slave trade, from which comes the modern, Western type of slavery. Despite being against the law, slavery continues in all parts of the world, including Africa.