This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book justifies the reason for studying the officers' lawful practice of threatening and using force during so-called critical events. It presents the theoretical framework, the research questions and introduces the researcher's approach, which is grounded in critical realism. The book focuses on the officers' chain of command enforcing the institutional response to a so-called 'critical event'. It addresses the contested idea of the existence in Italy of punitive institutions, which frequently emerge in the officers' accounts. The book focuses on the interactive practice of 'doing' coercion. It describes what occurs when the emergency squad's arrival and threats have not produced any de-escalation in violence. The book focuses on only a few particular issues which impact the process of ethnographic research within the walls. It concludes by discusses the relationship between prison officers and violence.