Distinct from the fear-based traumas associated with post-traumatic stress disorder (PTSD), the concept of moral injury is about transgressions of beliefs of right and wrong, and accordingly about feelings of shame, guilt and anger. As such, it has the interdisciplinary potential to fill the space left by the concept of PTSD. However, it requires development regarding the moral and sociopolitical dimensions of moral injury, which go beyond the conventional focus of psychological approaches. In philosophy, theology and social sciences, much has been written about trauma, morality and the sociopolitical aspects of mental suffering. This chapter discusses these insights, developing an initial perspective from which to approach military moral injury. It elaborates on the history of the concept of PTSD, discusses the increasing tendency to understand deployment-related suffering in medical terms, and reflects on both the potential and current shortcomings of the concept of moral injury. To address these shortcomings, it discusses multidisciplinary insights on the complex nature of morality and on what has been dubbed ‘social suffering’. In doing so, it sets the stage for examining, in the subsequent chapters, whether and how moral complexities at both the individual and sociopolitical level relate to experiences of moral injury among soldiers and veterans.