Sex and World Peace is a groundbreaking demonstration that the security of women is a vital factor in the occurrence of conflict and war, unsettling a wide range of assumptions in political and security discourse. Harnessing an immense amount of data, it relates microlevel violence against women and macrolevel state peacefulness across global settings. The authors find that the treatment of women informs human interaction at all levels of society. They call attention to the adverse effects on state security of sex-based inequities such as sex ratios favoring males, the practice of polygamy, and lax enforcement of national laws protecting women. Their research challenges conventional definitions of security and democracy and common understandings of the causes of world events. The book considers a range of ways to remedy these injustices, including top-down and bottom-up approaches to redressing violence against women and the lack of sex parity in decision-making. Advocating a state responsibility to protect women, the authors campaign against women’s systemic insecurity, which threatens the security of all. Sex and World Peace has been a go-to book for instructors, advocates, and policy makers since its publication in 2012. Since then, there have been major changes in world affairs, including the #MeToo movement, as well as advances in both theoretical and empirical literature surrounding the subject. This second edition, which adds coauthors Rose McDermott and Donna Lee Bowen alongside Valerie M. Hudson and Mary Caprioli, revises and updates the book for a new generation. The book retains its foundational overview of the relationship between women’s oppression and war, enhanced by fresh data and new material covering recent developments for global women’s rights and analysis of additional examples of gender and conflict throughout the world.