Recent interventions from a 'posthumanist' or 'new materialist' perspective have highlighted the embedded character of human systems within a 'panarchy' of human and non-human systems. Some of these discussions have influenced recent work in International Relations and Security Studies. Much of this work has brought a focus to the specifically material as a counterpoint to more idealist or subjectivist discussions. This article brings attention to a very particular element of materiality, one with a profound significance for issues of security -relations between human and non-human animals in instances of conflict.It is an indication of the deeply human-centred character of both International Relations and Security Studies that almost none of the central texts even mention the very significant roles that non-human animals have in the conduct of war. A central part of our argument is that the character of war, this key area of attention, itself would have been radically different but for the forced participation by an enormous range of non-human animals. Even though with the improvements in transportation over the last century non-human animals are less evident in the role of the movements of people and equipment, they still play a significant number of roles in the contemporary war-machines of wealthy countries.Drawing on literature from critical animal studies, sociology, and memoirs the article discusses the enormous variety of roles that non-human animals have played in the conduct of war. We also examine the character of human -nonhuman animal relations in times of war.