This article explores and theorizes an aspect of war in the 2020s that has not previously been recognized in social science literature: The practice of soldiers freezing their semen before joining the military. The security–demography nexus has been studied mainly as a state concern—whether a state should limit or expand its population depending on different factors. In this context, women have been the main targets of biopolitical reproduction efforts. However, societal and political shifts, coupled with advancements in reproductive technology that enhance accessibility, necessitate a re-evaluation of the gendered dynamics within the security–demography relationship. The war between Russia and Ukraine represents an unusual example of two industrialized states involved in an interstate war. The practice of soldiers freezing their semen constitutes a new masculinization of the security–demography nexus. We argue that the theoretical concept of reproductive insurance implies a form of self-governance that can manage shifting masculinities in ways that allow the male individual to protect the capacity to have children before risking life on the battlefield. The shifting gender dynamic of the security–demography nexusmeans that Western militaries may have to adapt their policies and offerreproductive insurance to both women and men within their ranks.