Do Duke Cosimo’s galleys, fortresses, and the crusading Order of Santo Stefano illuminate political, religious, and naval actions in the early modern Mediterranean world? This book firstly centers around Cosimo’s involvement in the last two decades of the Habsburg-Valois Italian Wars (1494-1559) with a special emphasis on the conflict’s naval dimensions and political episodes. Secondly, it deepens our understanding of Mediterranean galley warfare in terms of deployment, combat, administration, entrepreneurial and knowledge-exchange networks, and crusading. Finally, this account of the later Italian Wars and their reverberations into 1560s examines the interaction between warfare, politics, crusading, and sovereignty during this period.