During the struggle between Russia and Sweden for dominance in the Baltic in the early eighteenth century, hundreds, perhaps thousands of women were taken captive by Russian forces. Swedes, Livonians, Estonians, Karelians, and Ingrians were seized during the Great Northern War and incorporated into Russian households as servants, concubines, and symbolic trophies. Their experiences formed part of a broader early modern European pattern in which female captives were absorbed into militarized cultures through sexualized violence, coerced intimacy, and forced mobility. Within this system of domination, religious conversion became a central axis of negotiation, coercion, and survival. A striking example from the 1702 Baltic campaign is the future Empress Catherine I, whose conversion to Orthodoxy preceded her marriage to Peter I of Russia, though her ascent was exceptional. However, cases where captive women were forced or coerced into converting to Orthodoxy, often as a condition for marriage to Russian men, were quite common. Others naturalized voluntarily, while some, once repatriated, petitioned Lutheran communities to reverse their conversions, revealing the fluidity of confessional identity. Swedish polemical literature of the period also exploited the theme of forced conversion, drawing on hagiographic tropes of women who preferred torture or death to religious defection or sexual submission. This paper examines how religious coexistence, conflict, and negotiation unfolded in wartime settings and shaped the lives of female captives. Through case studies, I analyze patterns and rituals of conversion, primarily from Lutheranism to Orthodoxy, their flexibility, the treatment of children of mixed‑confession unions, and the ways conversion functioned as a gendered strategy of survival, adaptation, and limited agency within extreme power asymmetries.