slavery in where became didn't begin with the coming of the Portuguese .Communities fought each other and when a group is defeated, they are kept as prisoners of wars or captives. However the trade in slaves flourished around 16th century due to the influence of the slave merchants, the Portuguese. Its important also to note that the Arab slave trade took place up north as well.
The region of Benin was initially not into the trading of slaves However the sell of human cargo began to flourish following the coming of the Portuguese in the late 15th centuries. Benin Obas began to go to war with neighbouring communities to capture slaves which they either kept hostage or sold to the slave merchants in exchange for copper or manilla.
The human cost of Benin bronzes.
According to a researcher, Wu Mingrin , ""The metal required for the production of the Benin Bronzes was acquired in a form known as manilla. This was a form of money in the shape of bracelets that were usually made either of bronze or of copper. These were brought to the Benin Empire by European traders, and were usually exchanged for slaves and that these beautiful pieces of art were made possible by the heinous trade in human lives. The copper or manilla is now used by craft men to produce bronzes.Sometimes the slain heads of captives are forged into a bronzes. The immediate neighbours of Benin, the Igbanke(Ibo) and urhobos were majorly hit by the benin raiders .according to a report, a factory was built at agato(ughoton) for the processing of slaves for outward shipping. Benin also traded other commodities like pepper clothes.
Of all the kings of Lagos since Ado and Asipa, Akinsemoyin, Ologun Kutere, Eshinlokun, Akitoye, and Kosoko were the biggest slave traders, sending their fellow Africans to the Americas more than any other monarch.In fact, Oba Kosoko did what others never did. He bought back slaves already established in Bahia, Brazil because he needed their carpentry, masonry, and coopering skills to build Brazilian-type houses and produce European items in Lagos.
The Yoruba Wars began ensuring Brazilian ships with a seemingly limitless supply of captives bound for Salvador and points beyond. This final phase of the Atlantic slave trade, which officially ended in 1830 but remained a clandestine practice for years to come, resulted in a massive influx of Yoruba slaves. By virtue of being the last wave of mostly homogenous groupings of slaves to arrive in Salvador, they would leave one of the most visible and lasting cultural imprints on the growing Afro-Bahian community of Salvador, resulting in what Miguel Calmon called, “the brutal metamorphosis of Mangolas (Bantus) into Nagôs (Yoruba).” So dominant would their language and cultural customs become and so successful at assimilating others into their worldview would they be that by the middle of the nineteenth century, for many in Bahia, Yoruba culture became synonymous with African culture as a whole.
The Igbo, whose traditional territory is called the Bight of Biafra (also known as the Bight of Bonny), became one of the principal ethnic groups to be enslaved during the Trans-Atlantic Slave Trade. An estimated 14.6% of all slaves were taken from the Bight of Biafra between 1650 and 1900.
The Bight’s major slave trading ports were located in Bonny and Calabar.The majority of Igbo slaves were kidnapped during village raids.The journey for Igbo slaves often began in the ancient Cave Temple that was located in Arochukwu Kingdom. During this period, the three Igbo Kingdoms followed the same culture and religion, yet tended to operate very differently from each other. The Kingdom of Nri and the Independent Igbo States (confederation of independently ruled Igbo states) did not practice slavery, and slaves from neighbouring lands would often flee to these kingdoms in order to be set free.,Nri was considered a place of refuge.
In order to obtain European goods and weaponry, Arochukwu began to raid villages of the other Igbo kingdoms- primarily those located in the Igbo hinterlands. People would be captured, regardless of gender, social status, or age. Slaves could have been originally farmers, nobility, or even people who had committed petty crimes. These captured slaves would be taken and sold to European slave traders on the coast. Another way people were enslaved was through the divine oracle who resided in the Cave Temple complex. All Igbos practiced divination called Afa, but the Kingdom of Arochukwu was different because it was headed by a divine oracle who was in charge of making decisions for the king. During this time, if someone committed a crime, was in debt, or did something considered an "abomination" (for example, the killing of certain kinds of animals was considered an abomination due to its association with certain deities), they would be taken to the cave complex to face the oracle for sentencing.
Igbo slaves were unique because they were extremely hardworking and resourceful, but at thesame time rebellious and suicidal.