From a new RAND study prepared for the Department of Homeland Security, Stealing the Sword: Limiting Terrorist Use of Advanced Conventional Weapons [156-page pdf]:
In this document, we focus on how the United States can shape the environment, including the perceptions of terrorists, to discourage the use of advanced conventional weapons. We review weapons under development, assess prospective and previous terrorist uses of such weapons, identify ways to make particular kinds of weapons less attractive to terrorist groups, and explore reasons that terrorist groups choose or reject certain weapons.
The analyses presented here should be of interest to homeland security policymakers who need to understand the threat posed by advanced conventional weapons. Those concerned with developing security or defensive systems can allocate research and development and technology funding to countermeasures and defense systems with the greatest possible potential payoff. Those concerned with training security forces can adjust their curricula and concepts appropriately. And those interested in limiting the access of terrorists to advanced weapons can learn where to focus their efforts.
The most worrisome advanced conventional weapons that we have identified in this research are advanced, GPS-guided mortars. Only these systems combine a significant, new capability for terrorists with a lack of effective operational counters for security forces. We must take advantage of a fleeting opportunity to design controls into the weapons. This means that starting efforts to control advanced mortars now is urgent. Although seemingly less threatening, the other advanced weapons—sniper weapons, advanced small arms, antitank guided weapons, and limpet mines—still do require some responses.
Whether or not a terrorist group pursues a new, advanced weapon can be framed as a judgment about costs and benefits. In this context, the choice to seek a specific weapon will depend on the terrorist group’s assessment of how potential benefits compare with the costs of obtaining a weapon and on how the apparent costs and benefits of that advanced weapon compare with other tactical and technological options available to the group. This calculus may be an implicit rather than an explicit process, and decisions may be based on cost and benefit criteria that are idiosyncratic to the terrorist group. Nevertheless, a process with these basic components will underlie decisionmaking at the individual and organizational levels.
Such cost-benefit decisions are further complicated by uncertainty. Depending on the information available to the terrorist group at the time, it will face two different, but complementary risks. They are●the risk that the group’s cost-benefit judgments about the technology are incorrect and it is choosing to adopt a weapon that is not, in fact, supportive of its objectives
●the risk that the group’s attempt to adopt the technology will fail and it will pay the costs associated with doing so without gaining the desired benefits.
The effort to change terrorist decisionmaking about advanced conventional weapons can be viewed as targeting groups’ perceptions about the costs, benefits, and risks of acquiring and attempting to use the weapons.