Just war' is a disputed concept ever since its integration into Christian Ethics. The Roman Catholic Church has used the tradition of just war' for ages. It changed substantially since World War II and the Second Vatican Council. Also Pope Francis reassesses the use of force in international conflict. This book provides an indepth insight in this ongoing reassessment of just war' as part of Catholic Social Teaching. It does defend nor attack this tradition, but it provides a conceptual and analytical framework to understand both this tradition and the reasons for its reassesment.