Between its emergence in the 1870s and the beginning of the First World War, public perception of the anarchist movement and the theoretical and legal frameworks used to comprehend and control it underwent a dual process of criminalization and internationalization. The use of terrorism by anarchists was pivotal to these evolutions, as was its reception by alarmed populations and governments faced with unprecedented forms of political violence. Anarchism became increasingly identified as a political crime sanctioned by extensive laws at the national level and, at the internal level, by comprehensive protocols and extradition and deportation measures. These changes affected most European nations and the Americas similarly, making anarchism a clear instance of the globalization of militant politics. The “battle against international anarchism” was also a catalyst in the development of an international criminal system, as it accelerated the exchange of policing models and techniques.