This chapter examines the relation between army size, state expenditure, and warfare culture in sixteenth-century Portugal. It tackles directly one of the components of the military revolution debate, more specifically the mounting size of armies and the financial efforts that states had to develop in order to muster and maintain a large number of effectives, sometimes along several battlefronts, during the early modern period. Using sixteenth-century mainland Portugal as a case study, the chapter argues that this country did not witness the same rate of growth in army size, nor were the necessary economic, social, and political conditions met in the first place. The reasons to explain such a lack of progress go beyond economic and demographic factors. Political and cultural aspects equally determined the survival of a relative archaism into the sixteenth century and beyond. To demonstrate such an argument, a threefold analysis isapplied to the following topics: the evolution of the size of army and demographics; state expenditure; and warfare culture.