Abstract:Starting from the Iberian reaction to Machiavelli's ideas about religion and war, this article compares and connects Spanish and Portuguese theories of empire in the sixteenth and seventeenth centuries. Writings by Francisco de Vitoria, Martín de Azpilcueta, and Juan de Solórzano Pereira, as well as by less well-known thinkers, are used to trace the main legal and theological debates over empire that developed across the Iberian world. It is argued that the exchange of ideas about war and religion between Spain (...) and Portugal culminated in the theorization of a single global empire during the period of the Iberian Union (1580–1640). (shrink)