Counterterrorism consists of government actions to inhibit terrorist attacks or curtail their consequences. Such policies can limit attacks by confronting terrorists directly. For example, intelligence and police investigations resulted in the capture of the entire leadership of Direct Action (DA) in France between 1982 and 1987 (Alexander and Pluchinsky, 1992, p. 135; Hoffman, 1998). Italian authorities captured most of the Red Brigades after responding to a tip-off in the kidnapping of Brigadier General James Lee Dozier, the senior US officer at NATO’s southern European command, who was abducted from his home on 17 December 1981. He was freed unharmed in a daring police rescue on 28 January 1982. Based on state’s evidence obtained from Antonio Savasta, who was captured during the raid, the police later apprehended 200 Red Brigades suspects, which resulted in further arrests and the eventual demise of the group. Other counterterrorism actions can safeguard potential terrorist targets by reducing an attack’s likelihood of success or expected payoff. The installation of metal detectors in US airports on 5 January 1973 decreased terrorists’ probability of success, as did the fortification of US embassies in the mid-1970s and beyond. After 9/11, the deployment of federal screeners at US airports, the reinforcement of airplane cockpit doors, and the designation of no-fly zones in Washington, D.C., and other American cities were intended to limit terrorists’ success and, thereby, prevent attacks. In the extreme, counterterrorism can take the form of a military campaign against a terrorist organization. For example, the Sri Lankan army scored a decisive military victory over the Tamil Tigers on 16 May 2009, ending the group’s twenty-six-year struggle for an independent state.

The purpose of this chapter is to investigate and evaluate the two primary categories of counterterrorism policies – proactive and defensive. Proactive or offensive measures attack the terrorists, their resource base, or those who support them. By contrast, defensive or passive policies may erect a protective barrier around potential targets – physical or human. Such measures dissuade terrorists by decreasing their anticipated gains from attacks. This can occur if their costs are raised or their anticipated benefits are reduced. Defensive actions may also limit attacks if alternative nonterrorist actions are made more attractive. Defensive measures may involve limiting damage following a terrorist attack – for instance, enhanced first-responder capabilities or stockpiles of antidotes against chemical agents. Stiffer penalties and greater certainty of apprehension can dissuade would-be terrorists.