ENThe polities of the sixteenth-century Baltic competed and cooperated with one another and with local power groups in fluctuating patterns of rivalry and expedient partnership. Mercenarism thrived in this context, as early modern governments were seldom equipped with the fiscal and logistical tools or the domestic military resources needed to wholly meet the escalating challenges of warfare, while mercenaries themselves were drawn to a chaotic environment that afforded opportunities for monetary gain and promotion into the still-coalescing political elites of the region’s emerging powers. This study sits, like the mercenary himself, at the intersection of the military, the economic, the social, and the political. Broadly, it is an analysis of mercenaries in Livonian and Swedish service during the so-called Livonian War of 1558 to 1583. Mercenaries are examined as agents of the polities for whom they fought and as actors with goals of their own, ambiguously positioned figures whose outsider status and relative independence presented both opportunities and challenges as they navigated the shifting networks of conflict and allegiance that characterized their fractious world. The aims of this study are threefold. The military efficacy of Western and Central European professional soldiers is assessed in an Eastern European context, problematizing the notion of Western military superiority in a time of alleged military revolution.The effects of prolonged warfare on Estonian and Livonian society are examined with an eye on interactions between local communities and the foreign soldiery, as well as on the ramifications of increasing participation in military enterprise by segments of the Livonian population. Mercenarism is also analyzed as a key site of the early modern struggle for greater governmental control over the economy and legitimate violence, whether through the cooption of privileges traditionally enjoyed by non-state and local power groups or through partnership between these factions and centralizing governments.