Using the example of conflict escalation in former Yugoslavia, a common framework of the mechanisms leading to conflict escalation is developed in this paper. Escalation of ethno-nationalist violence is described as an endogenous feature of the nation. The principle of the nation may succeed in being an organising principle for integrating large-scale social groups. However, it may also generate the extreme event of ethno-nationalist violence. The architecture of a simulation model is described to test the extreme event hypothesis.