Trauma, the silenced aftermath of violence, has been largely neglected by international security studies, which perceives trauma as having little relevance to global politics. However, this article contends that trauma profoundly influences global security. Unless traumatic events are worked through, they can heighten insecurity not only in the immediate aftermath of violence but decades and even generations later. The article is divided into three parts. The first section examines trauma in general terms, noting its individual, social and political dimensions. The second section examines acting out in response to trauma, with a particular focus on the meaning-making narratives adopted in order to make sense of traumatic experiences: the heroic soldier, good and evil, and redemptive violence. These narratives serve to secure the state by shutting down questioning and showing strength and decisiveness in the wake of traumatic shocks. Section three examines the notion of working through trauma. Working through involves a process of mourning, in which past atrocities are acknowledged, reflected on, and more fully understood in all their historically situated complexity. It is a deeply political process that struggles to understand and challenge those structures and practices that facilitate traumatic loss.