Juris Pupcenoks develops a conceptual and theoretical explanation for why reactive conflict spillovers (political violence in response to conflicts abroad) occur in some migrant-background communities in the West but not in others. Using a rigorous, mixed-methods case study analysis, Pupcenoks comparatively analyses the reactions of the Pakistani community in London and the Arab-Muslim community in Detroit to the wars in Afghanistan and Iraq during the decade following 9/11. The key findings show that, with regards to activism in response to foreign policy events, Muslim migrant communities primarily politically mobilize on the basis of their ethnicity (not religion).