European ‘factories’ were created on the coast to control the slave trade.
The factories or forts were the holding place for slaves as they waited for the slave ships.
Europeans factors (people who collected the slaves on the coast) seldom ventured inland to capture the millions of people who were transported from Africa as captives. An African middleman would usually sell his slaves to the European factor.
Most Africans became enslaved through capture in wars and by raiding parties.
Warfare became more attractive to those that might more easily profit from it. War created captives, and thus potential slaves to profit from. Wars were not usually fought just for captives but the temptation to go to war increased.
As the demand for slaves grew, in some areas the impact destabilised existing kingdoms. Existing systems of governance based on kinship and consent were destroyed . In new kingdoms, such as Dahomey (established around 1600), raiding for slaves became a way of life for the armed elite. Frequent slave raiding meant it became harder to distinguish insider from outsider, as ethnic boundaries were churned up.