One of the misunderstandings about slavery is that slavery only took place in the Atlantic Triangle. European powers captured or bought slaves in West Africa and brought these slaves to the Americas. The focus is on West Africa and people tend to forget and did not know in the first place about the situation in East Africa. The island of Zanzibar was a hotspot of slavery with a famous slave marker. Slave traders travelled to the mainland and made long travels to catch slaves. On return the slaves could leave their heart and strength at Bagamoyo. The Arabs were the powerful force in East African slavery.
What has been the effect of this slave trade and of the slave holding at the Coast of Kenya and Tanzania. The Kenyan Joe Khamisi wrote about the situation at the Kenya Coast (now a haven for tourists), where his ancestors were slaves.
Read an interview with Khamisi here.