This thesis seeks to explain the determinants of resilient nationalist violence in Western Europe since World War II. Despite being one of the most affluent regions in the world, several episodes of nationalist violence arose from the late 1960s all over the continent. Faced with very strong states, these armed movements recurred to terrorist techniques of warfare to mobilize supporters and extract concessions from the goverment. However, some of the nationalist armed organizations succedded in building support and becoming resilient whereas many others failed and disappeared very quickly. In order to explain this variation, I contend that classical 'grievances' arguments must be complemented with 'mobilization' accounts of nationalist violence. Thus, the success of a terrorist nationalist organization in surviving does not only depend on the sources of grievance it can trigger in its fight against the state, but also on its capacity to create a large constituency of support that guarantees the steady flow of recruits, funds and legitimacy. In addition to grievances and 'mobilizational' incentives, this thesis also looks at the specific link between the political elites at the centre of the state and those holding offices at the regional level. If the dominant state-wide political forces also command the largest plurality of votes at the regional level, then state actors will have strong incentives to deal quickly with any nationalist challenge from the region under dispute. Regional politicians whose electoral fortunes depend on state-wide parties prefer reacting with some level of concessions if they expect the increase of nationalist mobilization in the absence of a positive state reaction. On the other hand, if regional politicians have autonomous sources of power - i.e., they do not run on state-wide party lists- state political actors will have more trouble in dealing with nationalist violence, since they must rely on the regional actors to assess the real demand for concessions. Whenever regional politicians are averse to change -because they anticipate that potential concessions will be paid by them-, they will advise state makers to repress nationalists. And if armed nationalists have potential to build their own constituency, state repression will contribute to that end. This combination of institutional 'unresponsiveness' and 'mobilizational' incentives can account for the existence of resilient armed nationalist organizations in Western Europe. I test this argument in two steps. First, I analyze a dataset with 30 observations of nationalist-prone European regions. The aim is to check whether the main argument fares empirically well in comparison to more standard explanations of nationalist violence. Second, I run three paired-wise comparisons to track in-depth the process of consolidation of nationalist violence. I compare the Basque Country, Corsica and Northern Ireland with Catalonia, Sardinia and Wales respectively. The main argument of the thesis works reasonably well to account for the observed variation, and it has also some implications for the potential emergence of armed nationalist movements in developing countries.