Brad Roberts’s scientific contributions

Recent national guidance has reemphasized the potential contributions of deterrence to the effort to reduce the risks of Weapons of Mass Destruction (WMD) terrorism. Those potential contributions can be brought into focus by disaggregating the militant Islamic extremist movement into the various components relevant to the intentions and capabilities for WMD terrorism. These components include the following: jihadi foot soldiers, terrorist professionals who provide training and other logistical guidance and support, the leaders of al Qaeda, groups affiliated by knowledge and aspiration (so-called franchises), operational enablers (i.e., financiers), moral legitimizers, state sponsors, and passive state enablers. In the period since 9/11, a broad base of social science research has emerged testing various propositions about how to influence these different actors. This research points to some useful insights, conclusions, and hypotheses. First, deterrence is not irrelevant to the effort to combat terrorism and to reduce the risks of WMD terrorism. Second, deterrence, like other tools of influence, is a strategy to create disincentives in an adversary's mind to courses of action he might otherwise adopt. Third, both modes of deterrence -- deterrence by the threat of punishment and deterrence by denial -- are relevant. But they operate differently across elements of the network/movement. Fourth, the cumulative effect of deterrence on the WMD terrorism threat is nearly impossible to predict, but three potential effects stand out: deterrence may succeed in lowering the lethality of individual attacks with WMD by inhibiting the cooperation of those most capable of developing and employing WMD in ways that reap their full lethal potential; deterrence may succeed in curtailing campaigns of attacks; and deterrence may induce the leadership of al Qaeda to utilize nuclear weapons only for purposes of deterrence and defense rather than for purposes of aggression and terrorism.