This paper brings a systems engineering approach to policymaking in the context of violent radicalization. We test strategies to combat terrorism under the premise that violent radicalization is a complex system of social contagion resulting in terrorism. We built a simulation using DIME-PMESII military standards to replicate a terror contagion occurring over 10 years in both physical and online environments under optimal, realistic, and worst-case scenarios. We then tested antiterrorism, counterterrorism, and counter radicalization strategies as policy experiments in this simulation. These experiments identified four key dynamics relevant for developing policies to reduce terrorism. First, most well-known policies are ineffective in containing terrorism driven by social contagion. Second, strategies generating backlash can become worse than doing nothing at all. Third, perceived grievance determines the carrying capacity of terrorism in a system, allowing disrupted networks to regenerate. Fourth, variable public support may result in sharp secondary waves of violence under certain contingencies. Experimenting with our model, we explore effective ways to address the violent radicalization problem.