A deadlier post-9/11 terrorism landscape for the USA abroad: a quasi-experimental study of backlash effects of terrorism prevention

The United States initiated sweeping counterterrorism efforts after the September 11, 2001 terrorist attacks. This study tests a backlash hypothesis as it relates to the nature of attacks against the US abroad. Relying on data from the Global Terrorism Database, this study uses a quasi-experimental design to investigate whether attacks against the US abroad became more or less lethal after 9/11. There is a significant increase in the proportion of attacks with fatalities and a significant decrease in the proportions of non-lethal attacks against US targets and interests overseas after 9/11. The results suggest a redistribution in the lethality of attacks against the US abroad. This study finds evidence of a backlash of deadlier terrorism violence against the US abroad after September 11. Examining for unintended consequences is an important facet of terrorism prevention research and policy.