The first draft of this work was presented to the University of London in December 1921, under the title of “The Arab Conquest of Transoxania”, as a thesis for the degree of Master of Arts, and was approved by the Senate in January 1922, for publication as such. During the year my attention was taken up in other directions and, except for the publication of two studies on the subject in the Bulletin of the School of Oriental Studies, nothing further was done until by the generosity of the Trustees of the Forlong Bequest Fund an opportunity of publication was offered. In its present form the work has been largely rewritten and revised. It makes no claim to present a complete historical account of the Arabs in Central Asia, but is intended solely as a critical study of the authorities in greater detail than has hitherto been made. Much is therefore omitted because it has already been dealt with in the standard histories. In order to keep down the cost of publication, the extensive references which originally accompanied the text have been cut down to a few notes at the end of each chapter. No references are given when, as in the great majority of cases, the authority for the statements made can easily be found in the appropriate place either in Tabari or Baladhuri.

I regret that several works which are indispensable for a thorough study of the subject have, for linguistic reasons, been inaccessible to me. Such are van Vloten’s Opkomst der Abbasiden, and almost the whole range of Russian research work. Through the kindness of Sir Denison Ross, however, I have been able to avail myself of a draft MS. translation of the most important and valuable of them all, Professor W. Barthold’s Turkestan, as well as of his as yet unpublished London lectures on “The Nomads of Central Asia.” My sincere thanks are due to Sir Denison Ross also for his continued interest and material assistance ever since he first introduced me to the subject; to Sir Thomas Arnold for much encouragement and helpful counsel; to Professor Barthold, who has read the MS. through and made a number of valuable suggestions; to the Trustees of the Forlong Bequest Fund for their kindness in undertaking the publication; and in no small measure to my wife, who has given much time and labour to preparing the MS. for publication.

London, April, 1923.