The brewing climate of fear and inter-ethnic mistrust has meant national leaders have been unable, and unwilling, to coordinate counterterrorism activities...In Europe’s fragile southeast, Islamism threatens to galvanize national rivalries and unravel two decades of cold peace. For the largely secular, moderate and west-leaning Balkan states, where religious kinship transcends borders, violent extremism is fueling fear, ethnic tribalism and seditious security agendas. And as Islamic State group fighters disband amid the siege against Mosul, the situation only promises to escalate.