Answer:
They competed to dominate the slave trade.
Step-by-step explanation:
One negative about the slave trade was that it tended to increase the amount of war that occurred in West Africa. The reason for this is that European (and American) slave traders did not simply go out into the African countryside and kidnap their own slaves. Instead, they bought slaves from the coastal kingdoms. Those kingdoms generally got slaves to sell through war and through raids against inland tribes. Because the slave traders wanted more slaves, the coastal kingdoms were encouraged to wage more wars and conduct more raids.