This book has been many years in gestation. On the one hand, it grew out of research on medieval maritime commerce and commercial law in the Mediterranean. On the other, it emerged from an interest in the Crusades. These two interests were drawn together in earlier research on shipping, transportation, and naval warfare during the era of the Crusades. A great deal of work still remains to be done in these areas, particularly in that of naval warfare in the Mediterranean during the period from the rise of the Italian maritime republics in the eleventh century to the end of the Crusades in the fourteenth. These concerns will be the subject of another work, yet to be completed, on the naval history of the Crusades.

In the meantime these studies are offered as a contribution to wider concerns with relations between Islam and Christendom across the Mediterranean over a more extended period of time. ‘Across the Mediterranean’ rather than ‘in the Mediterranean, or Mediterranean World’ because here the sea itself is the focus and centre of attention. It is considered at one and the same time as both the unique centripetal force bonding together the various peoples on all of its shores and also as the principal centrifugal element separating them and lying at the heart of their distinct historical developments.