The warring tribes of West Africa had much to do with the development of the transatlantic slave trade of the Europeans. The ambitious Asante tribe’s slave trade with the coast was blocked by the Denkyira tribe, so in 1701 the former invaded the latter to bring ivory and slaves to traders at the coastal European forts. Once tribes had access to the firearms and gunpowder of the Europeans, the slave trade with the latter flourished as stronger tribes wanted to maintain hegemony over weaker ones, which provided more slaves to trade.
Surplus Slaves of the Asante
“During the first two decades of the eighteenth century, Dutch trade along the Gold Coast had undergone a major transition, shifting from a predominant trade in gold to a predominant trade in slaves. The gold and slave trades had been intertwined from the beginning of European activity along the Gold Coast, but in a very curious way. When the Portuguese first started buying gold from African merchants at Elmina, they paid for it with cloth, metal goods, wine, and also with slaves . . . purchased from wealthy Africans to serve as porters on merchant caravans, workers in the gold fields, and agricultural laborers.
Between 1475 and 1540 more than twelve thousand slaves were imported into the Gold Coast by the Portuguese. After that slave imports declined, but forts such as Elmina and Axim continued to be major slave markets for slave brought into the Gold Coast. During the seventeenth century between forty thousand and eighty thousand slaves entered the region via the coastal ports.
When the Dutch drove out the Portuguese, they tried to maintain the distinction between the Gold Coast, which concentrated on the gold, and the Slave Coast, where they bought slaves. [Small] numbers of slaves – averaging less than two hundred per year – were exported from the Gold Coast on Dutch ships between 1675 and 1720. After 1720, however, there was a dramatic rise in Dutch slave exports from the Gold Coast: a thousand per year between 1721 and 1725, and two thousand per year between 1725 and 1730. The forts became sites where slaves were purchased and held until a company ship arrived to carry them away.
Prior to the 1720s, Asante had been capturing slaves in its wars, but it had used them internally for agriculture and gold mining. By the 1720s, Asante had built up such a large slave population . . . [and] Asante rulers felt free . . . to begin exporting their surplus slaves. In return for their slaves, they wanted mainly guns and gunpowder to support the further expansion of their growing empire.”
(The Diligent: A Voyage Through the Words of the Slave Trade, Robert Harms, Basic Books, 2002, excerpts pp. 134-137)