[Words Matter]

I tried to read it (”Arab Muslim World Architect of Slave Trade in Africa.”) on Google books but pages are not avaliable.

[Bookshelf]

In the 19th Century the largest collection of slaves were congregated in zaribas in the southern Sudan and controlled
by Zubeir Pasha. They could be moved to Egypt, to the Red Sea, or even into Libya. The black slaves were numbered in the tens of thousands.