The introduction explains how this essay articulates the issue of ‘justice after war’ from the point of view of just-war theory, and how such a view can and ought to impact upon international law, for instance by inspiring the eventual development of a new treaty, or Geneva Convention, exclusively concerned with issues of postwar justice. In the body of the essay, attention is first given to explaining why just-war theory has traditionally ignored, or even rejected, jus post bellum. Second, argument is made as to why this ignorance and rejection must be overcome, and replaced with information and inclusion. Third, principles drawing on traditional just-war theory are constructed and defended, for jus post bellum in general and for forcible postwar regime change in particular. Finally, several remaining challenges are addressed, seeking to dissolve doubts and strengthen resolve towards working for progress on this vital and topical issue of jus post bellum.