The paper defines terrorismand gives a rough classification of itstraditional forms: repressive terrorism,insurrectional terrorism ofethnic/national/separatist character andsocial-revolutionary terrorism. To explainthese forms of terrorism, scholars used twomodels: the psychiatric model and thesociological model. Both were – and are –not just objects of scholarly debate, butpart and parcel of a political conflictover the legitimacy of terrorist actions.In the last decade, new forms of terrorism(most prominent: fundamentalist Islamicterrorism) have developed as a reaction toglobalization and Empire-building. We haveseen a development from provincialterrorism to terrorism of global reach,from terrorism as a form of political crimeto terrorism as criminalized war. Thetraditional explanatory models have,therefore, to be supplemented by adiscussion of the dialectical relationbetween the growing American Empire and aspecific form of military opposition.Defined as terrorism, this opposition has,ironically, become a rather useful enemy inthe process of Empire-building. There ishope that the Empire will, in the not sodistant future, be able to monopolize thelegitimate use of military force,criminalize all other forms of violenceand, thus, turn the terror of wars into amere war on terrorism.