The topic of radicalisation is strictly linked to terrorism since, usually, the former leads to the latter. However, they are not synonyms, and the processes behind each are very different and complex to analyse. The radicalisation topic dominated public opinion following the surge of terrorist attacks in Europe by ISIS militants starting in 2015. These events led national and local institutions to commission projects and programs to tackle radicalisation by raising awareness on the topic in civil society. This paper aims to investigate radicalisation in European militaries to create a European framework in which armed forces and civil society can join to fight radicalisation processes related to armies. To do so, this analysis will focus on radicalisation processes within the military and amongst individuals who have left the armed forces.