For many centuries, from the end of the seventh century onwards, the Eastern empire and the barbarian kingdoms of the West clashed with the Islamic caliphate, in a war of conquest and reconquest which indeed became a clash of civilisations. And the Mediterranean became its theatre, or at least its main theatre, even when Arab dominance was replaced by a new power, that of the Ottoman Turks, who in the mid-fourteenth century besieged and took Constantinople, making it the capital of a new Islamic empire. This did not prevent the development of commercial relations and even political alliances between the two shores, as in trade between Italian coastal cities and the Arab terminals of the road to the Indies, and much later the French effort (starting with Napoleon’s expedition to Egypt) to colonise north Africa. Wars alternated with trade; but by now the Mediterranean had become – as it still is –europe’s frontier with another world, a different civilisation. But that is another story.