This work is the fruit of seven years residence on the Tanganyika Coast from 1952 to 1958. When I came to be stationed on the coast in 1952, I found there was much detailed information for the period after the coming of the Portuguese, particularly in the works of Justus Strandes and Sir Reginald Coupland. But no writer had considered the medieval period in detail: information about this period, and the ancient sites of the coast, many of which date from medieval times, was hard to find and scattered in a large number of works and monographs. I thus set myself to try to reconstruct the medieval period, by reconsidering the local documents available, by searching previous writers and by study of such sites as could be found along the coast.
There is still much more to be done, for, while there are rumours of many documents, few new ones have come to light. In archaeology, although it is possible to describe a great number of sites, only two small and limited excavations have taken place. The trowel of the archaeologist is urgently needed to begin where the historian must perforce leave off: there is much yet to be learnt of social and economic life.
Work of this kind cannot hope to be popular. Yet the detailed spade-work of the historian must precede what may be palatable to the general reader. It was my great good fortune that my study attracted the notice of my friend Dr A. H. J. Prins, of Groningen University, Netherlands, who invited to it the attention of Professor E. Dammann, of the African Institute of the Humboldt-University of Berlin, himself long a resident in Tanganyika. I cannot repay their kindness in having brought it to the attention of the Deutsche Akademie der Wissenschaften zu Berlin, which has done me the honour of accepting it for publication.
There are many others too to whom I owe gratitude for encouragement, assistance and kindness. First is the Revd Gervase Mathew, F. S. A., my friend and master now for more than twenty years. Dr John Walker, Keeper of the Department of Coins and Medals in the British Museum, most kindly guided my first footsteps in the numismatics of the region, and Dr William Cohn, formerly of the Cologne Museum, initiated me into the study of Chinese porcelain. Sir John Gray most courteously permitted me to make use of his unpublished translation and notes of the Portuguese version of the Kilwa history, but what appears here represents my own opinion. Dr P. A. Lienhardt was good enough to check my translation of the Arabic version of the Kilwa history, and has kept my feet in the straight path on numerous points of detail. My kind friend the late Sir Eldred Hitchcock, C. B. E., allowed me access to his collection of imported Chinese porcelain and gave me much encouragement: his recent death is a grievous loss to those interested in East African history. I am grateful, too, to Sir Mortimer Wheeler, C. I. E., M. C., for much encouragement; and likewise to J. S. Kirkman, Warden of the Coastal Historical Sites of Kenya, R. E. S. Tanner, lately District Commissioner, Pangani, and G. W. Hatchell, O. B. E., for having read the text and given me various suggestions: as also to those who have allowed me access to coins in their possession or under their care: Mrs D. G. Cameron, Dr E. Maercks, Mrs G. E. Organ, Miss E. Oxtoby . . .