It is assumed widely that 'war made the state' in seventeenth-century France. Yet this study challenges the traditional interpretations of the role of the army as an instrument of the emerging absolutist state, and shows how the expansion of the French war effort contributed to weakening Richelieu's hold upon France and heightened levels of political and social tension. This is the first detailed account of the French army during this formative period of European history. It also contributes more generally to the 'military revolution' debate among early modern historians.