Simple analytics of the impact of terror generation on attacker–defender interactions

A simple Attacker-Defender interaction is analyzed, in which a single terrorist (denoted T) may attack a single target in the homeland of a government/state (denoted G). The interaction is modelled as a one-shot sequential move game in which G first chooses how heavily to defend the target, after which T chooses whether or not to stage an attack. T’s benefit from a successful attack is allowed to be increasing in the quantity of resources that G allocates to defense. In the context of terrorism, that assumption has multiple reasonable interpretations, including situations in which: (i) citizens of the target country are terrified to a greater degree when a more heavily fortified target is attacked successfully or (ii) a successful attack on a more heavily fortified target allows the terrorists to recruit more effectively. The amount by which T’s benefit from a successful attack exceeds its baseline owing to greater defensive efforts by G can be thought of as a terror effect. Such an approach differentiates terrorism from traditional conflict in an important way. For the specified model, defensive efforts by G necessary to prevent T from staging an attack are increasing in the magnitude of the terror effect. Moreover, if G inaccurately underestimates the magnitude of the terror effect, then G might choose either less than or more than the optimal level of defense, with the realized outcome depending upon model parameters. The results highlight the importance of correctly understanding the payoffs and motives of terrorists in order to be able to allocate defensive resources optimally.