This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book argues that terrorism is in all its atrocity, a political act. As Professor Jan Klabbers has pointed out, “international law has great difficulty in deciding whether terrorists should be treated as ordinary criminals or as political actors.” The book argues that this difficulty strongly relates to the so-called political offence exception (POE) to extradition protecting political offenders from extradition. It discusses a thorough analysis of a vast number of historical sources, demonstrates the important changes in how terrorism has been dealt with, and highlights some intriguing historical analogies. The historical foundation for the analysis lays on a wide variety of historical scholarship providing knowledge and understanding of the most important political changes that can be linked to the motivations behind the limiting of the POE as well as the de- and repoliticisations of terrorism.