This study examines the effect of foreign military interventions on the incidence of suicide attacks. It presents three theoretical explanations. Foreign military interventions may boost insurgent use of suicide attacks by (a) fomenting a nationalist backlash that sanctions the use of more extreme and unconventional tactics like suicide attacks, (b) providing more and better targets against which suicide attacks can be launched, or (c) prompting insurgents to use suicide tactics in order to overcome their power asymmetries and to confront better defended targets that are enhanced by interventions. We test these competing explanations using a battery of statistical tests on cross-national, time-series data for 138 countries during the period from 1981 to 2005. We find that only foreign interventions with specific features—pro-government interventions involving larger numbers of ground troops—boost suicide attacks in countries experiencing interventions. This finding suggests that by tipping the balance of power against insurgents and hardening targets in the context of assisting a local government, foreign military interventions are likely to increase the use of suicide attacks by regime challengers.