CEP Senior Advisor Prof. Ian Acheson writes: Today’s terrorist threat is more diverse and unpredictable than in 2005. Our resilience against violent extremism is hollowed out by institutional timidity. We still face tactical, technical and operational obstacles hampering disaster response. While Islamist extremism is supported by a tiny fraction of Muslims, virulent anti-Semitism has taken hold within and animates hatreds, the precursor for domestic terrorism, from events thousands of miles away. These challenges require a strong response, putting country before political calculation or progressive distractions.