Was there an early modern military revolution in mainland Portugal? I propose a deliberately contradictory and, hopefully, complex answer. I hypothesize that the kingdom’s peculiar insularity was a result of the overdetermination of its peripheral geographical position from the consequences of the evolution suffered by Hispanic and English monarchies. Simultaneous concern about both European and overseas issues was a common feature of several European states, but in the case of Portugal, there is a marked disproportion between the influence on European and overseas affairs.