Conflict related sexual violence is a phenomenon which causes devastation to innocent civilian populations and has lasting implications beyond the serious physical violation. This dissertation explores the causation of sexual offending during war through a predominantly offender perspective by examining different case studies, which are intended to demonstrate both similarities and differences in its occurrence. Through theoretical frameworks and analysis of military structures and cultures the commission of sexual violence can be understood to be complex and rooted in the politics, culture, ethnicity, and religion of the individual context. The title of the thesis ‘War has entered the blood’ is definitive of the distinguishable transition between peace and war time and its influence on the perpetration of sexual violence. Connections between time periods are undeniable, however, the breakdown in social order and shifts in governing powers allow for changes in behaviour which are influenced by internal groups dynamics and hierarchal structures in the armed forces and in many cases alter the type and severity of sexual violence. The research extended to examine the variation in sexual offending as opportunistic, as a practice, as a weapon of war and as a form of genocide. Each context analysed demonstrated how perpetrators exploit the obvious vulnerabilities of the target population through sexual violence to gain advantage for various purposes. Changes to behavioral norms during war appear to elevate violent tendencies with rape becoming exceptionally brutal. Assessments of legal responses to conflict related sexual offending demonstrated the challenges associated with prosecuting offenders and how individual cases have reoriented international criminal law and its focus on this serious crime. This process has not been linear, and the cases chosen for analysis suggest that the law works in tandem with external sociological and political elements and remains a work in progress. The research predominantly indicated that the perpetration of sexual violence as an individual isolated offence is less frequent than it being employed as a practice or systematically. In some of the regions examined the practice of sexual violence was due to permissive and tolerant attitudes of commanders and in other instances formed part of a military and governmental strategy which was planned in advance. The range of territories chosen, the former Yugoslavia, Palestine, Rwanda, and the Democratic Republic of Congo formed an important part of the research as it demonstrated past and present contexts which have experienced sexual offending during war. Analysis of each region provided a wealth of information which highlighted the patterns and distinct differences in how sexual violence is commissioned.