A new edition of the classic text on Crusader castles and their relation to the military architecture of the West, written by T. E. Lawrence (of Arabia) while still an undergraduate at Oxford in 1910. At the end of the nineteenth century, it was generally assumed that these castles were the prototype for the massive buildings erected in Northern France and England in the twelfth and thirteenth centuries. Lawrence opposed this view: unlike most earlier writers on the subject, he was already familiar with castles in England, Wales, France and Syria as a result of a series of expeditions made on bicycle or foot, culminating in 1909 in a three-and-a-half month walking tour of the Levant. Although his thesis was to guarantee him a first-class degree in Modern History, its impact on scholarship was slower to take effect. The typescript remained virtually unknown until 1936, a year after the author's death, when it appeared in a limited edition of the Golden Cockerel Press. Crusader Castles is now offered to a wider readership. The original text is reproduced without alteration; but a selection of the pencilled notes which Lawrence added to the typescript, in preparation for a revision that was never made, are included as footnotes, together with additional editorial notes and bibliographical details. Lawrence's work is also assessed in the light of seventy-five years of subsequent research, in an introduction prepared by Denys Pringle.