Final answer:
When Europeans arrived in sub-Saharan Africa during the 1400s and 1500s, the African slave trade was already established, but the arrival of Europeans transformed it by providing firearms and manufactured goods that appealed to West African polities, leading to the militarization of states and the reorientation of African trade.
Step-by-step explanation:
When Europeans arrived in sub-Saharan Africa during the 1400s and 1500s, the state of the African slave trade was already well-established. Slavery had been a traditional element in African societies for centuries, with captives acquired through war or as payment of debts. However, the arrival of Europeans, with their firearms and manufactured goods, transformed the nature of the slave trade in Africa. European powers like Portugal, Spain, England, France, and the Netherlands, along with their wealth, firearms, and manufactured goods, appealed to West African polities, who enriched themselves by providing captives to the Europeans in exchange for goods like guns. This resulted in the militarization of states and the reorientation of African trade.