This work was supported by the Centre de recherche de l’école des officiers de la gendarmerie nationale (Gendarmerie nationale, CREOGN, Melun, France); the Paris-Sorbonne Université (commission recherche de l’université, Centre d’histoire du XIXe siècle, École doctorale 2 histoire moderne et contemporaine); the Institut de Recherches historiques du Septentrion (Irhis), U. Lille; the French Service historique de la défense; the Centre d’histoire du droit et de la justice, UCLouvain; the research programme “Justice and Population” (Interuniversity Attraction Pole P7/22, Belgian State—Belgian Science Policy); the Région Nord-Pas-de- Calais (Accueil “Jeunes Chercheurs 2015”). We would like to thank Professor Jean-Noël Luc (Paris-Sorbonne Université) for his long-term help, support and enthusiasm for police and gendarmerie matters. This book is also in part his book. We must thank Floriane Avancès, Maëlle Besson, Alexandre Combralier, Maxime Delaude, Marianne Devillers, Enguerrand Ducourtil, Jean-Gatien Gilbert, Ladislas Latoch, Gabrielle Legourd, François Mathou, Vincent Perrot, Laetitia Plaissy and the history graduate students at the Sorbonne University who assisted with the translation of conference proceedings— a special thanks goes to Mathilde Lepez who worked on three chapters. Among our professional translators, Dr. Jean-Baptiste Picy (Lateral Traductions) provided us with invaluable help in terms of both his talent and commitment—contributing greatly to make this ambitious project possible.