Answer:
The Trans-Atlantic slave trade would not have been possible without the cooperation of African leaders who exchanged slaves for trade goods.
Explanation:
The trade in African slaves -- both on the Atlantic coast (from around 1503 to 1853) and the Indian Ocean (more or less continuous from Ancient times, and still not completely stamped out) -- has always depended on local parties supplying slaves.
"Sailor, beware the Bight of Benin, for there are few who come out though many go in." -- Traditional, Sailors Rhyme.
The Trans-Atlantic Slave trade began with the first Portuguese shipment of slaves to the New World in 1503 and was repressed after the end of the Napoleonic Wars. During that time, the European presence on the West African coast was severely limited, largely by the disease environment. Moreover, until the late 19th Century, military expeditions into the African interior were easily avoided or defeated.
While European raiding for slaves could occur, this was rare and hazardous for the raiders. The Atlantic Slave Trade depended on local African leaders to provide captives (or their own people), in exchange for trade-goods.
During the centuries in which the Trans-Atlantic Slave Trade continued, there were over 100 cities/towns/kingdoms or tribes involved in selling slaves for export. The slaves were war-captives, criminals, or often just other members of clans and families different from their ruler. The Dahomey used to kill large numbers of their own people every year, until they realized it was more profitable to sell them.
African tribes and kingdoms that were heavily involved in providing slaves included the Oyo, Igala, Kaabu, Asanteman, the Aro Confederacy and Imbangala war bands. The Kingdoms of Benin, Dahomey, the Manikongo, and of the Bambara and the Khasso were also heavily involved.
The trade-goods used for the slave-trade tended to be inexpensive European manufactured items -- dinner-ware, pots, cloth, tools, firearms and ammunition, spirits, and food.
