The establishment of Norman naval supremacy in the central Mediterranean during the twelfth century was far-reaching and momentous. The impact went well beyond the Normans in particular and southern Italy in general. It was at the very nexus of change on the ‘middle sea’, a change that would affect the course of events not only in Europe, but also in the Middle East and North Africa for generations. It would not be an overstatement to characterize it as a multifaceted, pivot point in history with wide-ranging military, political and economic effects on a large number of peoples in vastly varied regions. That being said, the impact can best be broken down into four major and immediate consequences: firstly, the Norman conquest of the central Mediterranean facilitated the eastward expansion of West Italian sea power, namely that of Genoa and Pisa, in conjunction with the Crusading movement; secondly, it engendered Western commercial growth both north-to-south and east-to-west; thirdly, it altered forever Muslim trading patterns across the Mediterranean; and finally, it laid the groundwork for the resurgence of Sicilian sea power under Frederick II.

Eastward expansion of West Italian sea power

Prior to the eleventh century, Muslim domination of the central Mediterranean acted as a brake on Western commercial expansion. Muslim control of Sicily and the lands immediately to the north and south meant that West Italian maritime commerce was largely restricted to the Tyrrhenian basin.