The reissue of this book in paperback form provides a welcome opportunity to address some of the issues concerning the studies that comprise it which have been raised by friends, colleagues, and students, both in print and informally. Because this is a book which is focused on issues and developed through theses, it has, in fact, attracted a good deal of comment. Naturally, I have been gratified by the favourable nature of much of that comment. However, not everyone has agreed either with the theses concerning the nature of Mediterranean geography and medieval technology or with the application of these to particular historical studies. Some of the more critical comment that has been made stems from a misunderstanding of the purpose of the book and from a tendency to attribute to it a wider compass than its limitations permit. Readers should be aware from the outset that this book is not, and never was intended to be, a general maritime history of the Mediterranean world in the Middle Ages. The subtitle is very deliberate. The studies contained in chapters 4 to 8 are both selective and selectively treated. They are intended to provide historical testing grounds for the theses developed in the first three geographical and technological chapters, and no more than that. They encompass neither the entire maritime history of the Mediterranean in the period nor even all aspects of the conflict and competition between the civilisations with which they deal.