Virtuous Aggression looks at potential influences on the development of ethno/national separatist terrorist organizations. It analyzes several theories that attempt to explain nationalist and terrorist movements in order to build a working paradigm for this research. It also examines the origins of Basque and Catalan terrorism, and Roma passivity, in Spain in order to identify background conditions with the potential to influence these movements. This study then evaluates these variables using a logit regression model. The logit model assesses two-hundred ninety-seven minority populations within one-hundred twenty-six states, primarily between 1945 and 2003. The results show several factors influencing the formation of these organizations. These findings suggest that it is possible to detect populations and environments with increased potential for producing nationalist-based terrorism, and that by addressing those conditions facilitating its development, it is possible to reduce the potential for additional ENS movements to develop into terrorist organizations.