"In evaluating the African slave trade, there was another "Middle Passage" often neglected by most scholars—the Arab slave trade. It is often forgotten that the Arab slave trade in East Africa and the slave trade from North Africa into Inner West Africa was protracted and ruthless. Sometimes the Arabs from the north who were Moslem enslaved Africans in the south who were also Moslems, thereby violating one of the most basic customs of their faith—that no Moslem should enslave another Moslem. There is a small library of books on this subject that most scholars have chosen not to read, thereby making the Arab slave trade the best kept secret in history—although it is not a secret at all. Of the many books and documents that I have read on the subject, Slavery in the Arab World by Murray Gordon, 1987, and The African Slave Trade From the 15th to the 19th Century, in The General History of Africa: Studies and Documents 2, UNESCO,1979. I find the most informative the UNESCO book, especially the chapter, "The Slave Trade in the Indian Ocean."
Like most strangers to Africa the Arabs entered Africa, allegedly. as friends. The Africans who are curious and uncritical about new people, new religions and cultures treated the Arabs as well as they treated other strangers. The Arabs were not always kind in their spread of Islam in Africa. In fact, they were usually ruthless and often disrespectful of societies and cultures that existed in Africa before they arrived. In North Africa the two wars of Arab conquest that came in the seventh and tenth centuries, the first being religious and military, broke the back of Roman influence in the area and replaced the corrupt Roman regimes. At first the Arabs were welcomed in North Africa as a replacement for the ruthless Romans. When the North Africans and Berbers discovered that the Arabs were also ruthless, although in a different way, it was too late because the Arabs now had the military upper hand.
Another aspect of Arab conquest, generally neglected, is the spread of Arab influence in East Africa through accommodation and sexual conquest. Many times the Arabs moved down the coast of East Africa rendering the service of the much needed East African coastal trade. Soon after this, Arabs began to marry or cohabit with African women. This in turn resulted in a generation of African-looking Arabs. These Arab half-breeds facilitated the spread of the trade inland at a time when the Arab face was held in suspicion in this part of Africa. In the fierce competition in the West African slave trade, the Portuguese were driven from West Africa around to East Africa. The Arab slave trade, moving from north to east met the Portuguese slave trade moving up from the south. These two slave trades complemented each other and culminated with the establishment of one of the largest slave trading forts, in the history of the world, on the Island of Zanzibar. This event is well documented in any good history of East Africa, including the Cambridge History of East Africa, and The Cambridge History of Africa. Basil Davidson's A History of East and Central Africa to the late 19th Century, and certain chapters on East Africa in his Lost Cities of Africa is a popularization of the subject. There are two old but valuable books on the subject, East Africa and Its Invaders by Reginald Coupland, and the chapters on East Africa in the book, The Colonization of Africa by Alien Races, by Sir Harry Johnston."http://www.nbufront.org/MastersMuseums/JHClarke/EdRealityAfricanWorld/EdWorldPart3.htmlEducation for a New Reality in the African World was prepared for The Phelps-Stokes Fund and delivered on November 14, 1994 in a ceremony at which Dr. Clarke was presented with their highest award, the Aggrey Medal, for "recognition of his unique contribution contribution to our knowledge and understanding of African civilization."http://www.nbufront.org/MastersMuseums/JHClarke/EdRealityAfricanWorld/EdWorldContents.html