The article reconstructs Shklar's thoughts on war. It argues that these thoughts constitute a crucial pillar of her political theory. Of particular significance is the interpretation of her book Legalism, where Shklar criticised efforts to streamline the complex issue of the causes of war into a simple theory of power and aggression, and her work on Montesquieu, which ultimately allowed her to link thoughts on war and extraordinary cruelty to her interest in cruelty as an ordinary vice. In this way, the article answers the question about the relationship between Shklar's explicit cosmopolitanism and her negative political theory. It demonstrates that her thoughts on war were politically cosmopolitan, while allowing her to eschew the type of global ethics that underwrites just war theorising, she was critical of. The article makes a case for considering Shklar's work as a contribution to Global Political Theory, calling for the latter to look beyond the just war tradition to pursue its interests in both theoretical prescription and political reality. This because Shklar's thoughts on war successfully combined empirical analysis of world affairs with normative dismissal of human actions that place others in situations of existential fear.