Guns, money, and other trade goods, like tools and woven cloth .
it was wonderful if you were a wealthy white land owner, and not so great if you were an african.
Some African nations lost some ethnic groups to the slave trade as well as some African nations had in influx of white persons to "civilize" the countries. After the slave trade returning Africans...
Nothing but the food required to keep them going.
because they were dying of diseases and because diseases were spreading