A Mixed Methods Exploration of the Relationship between Target Hardening and Differential Terrorist Attack Outcomes

Abstract

We used a convergent mixed methods design to explore the relationship between target hardening and the successfulness of terrorist attacks for 94 jihadi-inspired incidents in the United States between 1990 and 2018. Our quantitative analysis reveals that only 12% of incidents with no target hardening were unsuccessful, whereas over 80% of incidents with a law enforcement/military presence and physical/electronic security were unsuccessful. Qualitatively, we examined four case studies to contextualize these findings and explore the nuances in the relationship between target hardening and attack outcomes. We conclude that target hardening must be tailored to the size and scope of a potential target and may be most effective when several different mechanisms, capable of detecting and addressing potential threats, are leveraged simultaneously.