The occurrence of a disaster exposes the vulnerability and resilience of the affected community. For the same reason, disasters represent windows of opportunity to modify these conditions. But is it really so? Is a disaster followed by a modification of the conditions of vulnerability that caused it or of the factors of resilience that mitigated its effects? And if so, at which conditions and how? This article tackles those questions via the historical analysis of post-disaster transformations. It focuses on seismic disasters, which are the main area of expertise of the author, but hopes to offer reflections that speak also to other kind of disasters. The analysis is grounded on a comparison between the 1908 Messina earthquake and the 1968 Belice Valley (Italy) earthquake, but makes reference also to other disasters. Based on this empirical evidence, the article sheds light on how post-disaster politics can transform those factors that contributed to the disaster as well as factors that can contribute to overcome it. The article focuses notably on three themes: the nexus between disaster interpretations and prevention policies; the long term consequences of emergence choices; the structures of institutional memory. These three themes illustrate how the modifications or the persistence of conditions of vulnerability and resilience depended on tensions and conflicts among multiple actors and their conflicting intentions. These intentions often do not correspond to those of disaster prevention and can produce, over the long term, unexpected consequences.