Over the course of the late-thirteenth and fourteenth centuries–as they subdued, expelled, and enslaved Muslim populations–the kings of the Crown of Aragon recruited thousands of North African cavalry soldiers, whom they called jenets, to serve in their armies as well as in their courts as their personal protectors, members of their entourage, and even, on occasion, their entertainment. Grounded in Latin, Romance, and Arabic archival sources from Spain and North Africa, this work seeks to explain this alliance of the Christian Aragonese kings with foreign Muslim soldiers. It details not only how and why the Aragonese kings recruited and relied upon Muslim soldiers but also the origins and motivations of these soldiers. This book argues that far from marking the triumph of secular tolerance over religious intolerance, the alliance between the Aragonese kings and the jenets both depended upon and reproduced ideas of religious difference. More precisely, it argues that this history of interaction should be understood within evolving and intertwined Christian and Islamic ideas about sovereignty, religion, and violence. In recruiting Muslim soldiers, the kings of the Crown of Aragon invoked a deep and shared imperial tradition that bound rulers and religious others in the medieval Mediterranean.