My doctoral dissertation, entitled “Thinking War and the Military. An Analysis of the Impact of the End of Roman Peace on Society in a case study on early Christian Gaul (400-700)”, deals with the question what impact the end of Roman peace had on late Roman and primarily early medieval society, by using the example of fifth to seventh century Gaul. To this end, the study focusses on society as it was and the world of thought of those who lived in it. As the study aims at analysing the societal transformation following the breakdown of quietude, it primarily focusses on the significance that was attributed to war and armed violence, and the function and status of those who fought. Although the analysis is primarily based on written evidence, it also accounts for archaeological remains. The analysis comprehends a linguistic approach by focussing on changes in the terminology used to refer to core ideas and concepts related to the world of war. The study is undertaken in four main steps: a first structural analysis focusses on the changes contemporary society went through between the fifth and seventh century. The second part of the thesis mainly comprehends an analysis of the perception of known authors and the direct testimony they provided. In order to find out what significance contemporaries attributed to warfare and those who fought, the third and most extensive chapter focusses on the role and significance of armed violence and the military, and analyses the requirements they were expected to comply with. The last chapter is an analysis of martial ideas and concepts as they were more and more frequently found in Christian writings, in order to show that not only those who fought gradually conformed to Christian requirements, but that the Church also adopted significant ideas and values, which until then had primarily belonged to the secular world. Although it has never been doubted that the early medieval society was characterised to a significant extent by military violence, the world of thought of those who fought and their role and function in the post-Roman world have only been studied very marginally until the present day. As the focus of a majority of the studies that have been undertaken until now foremost focussed on the role of the newly established Christian religion, the significance of war and violence as a factor of societal change has largely been neglected. This study aims at being a first attempt to analyse the post-Roman world of war from a sociological and ideative perspective, by focussing less on history of events than on the experience of those who were actually concerned by these occurrences. It argues that war was a much more significant factor of change than assessed until now, and that this does not necessarily imply that societal transformations were not a basic part of an only gradual collapse of the Roman world.