Deterring Terrorism: Theory and Practice

Deterring Terrorism: Theory and Practice

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Product Details

ISBN-13: 9780804782494
Publisher: Stanford University Press
Publication date: 09/19/2012
Edition description: New Edition
Pages: 352
Product dimensions: 8.80(w) x 6.00(h) x 0.80(d)

About the Author

Andreas Wenger is Professor of International Security Policy and Director of the Center for Security Studies at the ETH Zurich (Swiss Federal Institute of Technology), Switzerland.

Alexander Wilner is Senior Researcher at the Center for Security Studies at the ETH Zurich, Switzerland.

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Deterring Terrorism


Stanford University Press

Copyright © 2012 Board of Trustees of the Leland Stanford Junior University
All right reserved.

ISBN: 978-0-8047-8248-7

Chapter One


Jeffrey W. Knopf

Prior to 9/11, there was little research on deterring terrorism. Some terrorism specialists expressed skepticism about using a deterrence framework to combat terrorism, but most terrorism researchers did not examine this strategy in detail. Deterrence researchers in the field of security studies, meanwhile, focused on the strategy's uses in relation to interstate conflict, especially at the nuclear level, and generally ignored terrorism by non-state actors.

This changed after the September 11 attacks. A conventional wisdom quickly emerged that deterrence would prove irrelevant against groups like al Qaeda. Skeptics expressed doubt that deterrent threats would sway either individual terrorists, who are willing to commit suicide for their cause, or terrorist organizations, who "lack a return address" against which to retaliate. Ironically, as the prospects for deterring terrorism started to appear more daunting, scholars began seeking to adapt deterrence to meet the new challenge. The result has been a sizable body of new research on deterring terrorism.

Elsewhere, building on earlier work by Robert Jervis that identified three waves in deterrence research, I have described the recent research on deterring terrorism as being part of a broader fourth wave in deterrence research. The fourth wave includes reflections on the appropriate role of deterrence in general after the Cold War and research on the prospects for deterring rogue states armed with weapons of mass destruction (WMD). Research on deterring terrorism, however, constitutes the largest and most original part of the fourth wave, and it will be the focus of this chapter. The goal of this chapter is to provide a classic literature review. It summarizes the key developments in the literature, identifies the main points of consensus and remaining disagreement, and draws attention to the most important gaps and problems in the recent research.

The most important point on which there is a near consensus in the literature is that deterrence remains relevant in dealing with terrorism. But given the many challenges involved, scholars also agree that the strategy is unlikely to be 100 percent effective. Current research on deterring terrorism therefore focuses on improving results at the margins, not on achieving perfection.

Three approaches to deterring terrorism have received the most supportive commentary. The first approach involves deterrence that is indirect in nature, intended to pressure third parties who facilitate terrorism rather than terrorist operatives themselves. The second approach reflects a return to Glenn Snyder's old concept of "deterrence by denial." The third approach, consistent with a general trend in the fourth wave toward broadening the concept of deterrence, explores sources of deterrence that are nonmilitary in nature, such as "deterrence by delegitimization." The area of greatest debate concerns traditional notions of deterrence by punishment, in particular the efficacy of threatening retaliation against the communities that terrorists claim to represent. Because there is considerable disagreement about the likely effects of seeking to deter terrorism through threats of societal punishment, classic punishment approaches have not been endorsed and elaborated in the literature as widely as the other three approaches listed above.

The rest of this chapter proceeds as follows: It first reviews literature that focuses on conventional terrorism. This section summarizes indirect, denial, and punishment approaches. The chapter then reviews literature that focuses explicitly on WMD terrorism. This discussion summarizes the most innovative of the nonmilitary approaches, which involves seeking to delegitimize and thereby ensure a public backlash against WMD terrorism; this section also highlights dilemmas involved in trying to hold states accountable as potential sources of nuclear materials. The chapter concludes by identifying a need for more empirical research and calling attention to possible trade-offs involved in the various proposals for deterring terrorism.


The suggestions in the fourth wave for deterring conventional (that is, non-WMD) terrorism are organized below into indirect, denial, and punishment approaches, respectively. Delegitimization approaches are not addressed here because they have been proposed mainly in connection with threats of nuclear terrorism. Suggestions for deterring WMD terrorism are dealt with separately in the next section.

Indirect Deterrence

Most of the core ideas for how to apply deterrence to terrorism appeared fairly soon after 9/11. A short book published in 2002 by Paul Davis and Brian Jenkins of RAND was especially influential. Their key insight involved disaggregating a terrorist network into its component elements. Although the suicide terrorist who has hijacked an airplane is almost certainly beyond the reach of deterrence, other actors involved in terrorism might not be. As Davis and Jenkins put it:

It is a mistake to think of influencing al Qaeda as though it were a single entity; rather, the targets of U.S. influence are the many elements of the al Qaeda system, which comprises leaders, lieutenants, financiers, logisticians and other facilitators, foot soldiers, recruiters, supporting population segments, and religious or otherwise ideological figures. A particular leader may not be easily deterrable, but other elements of the system (e.g., state supporters or wealthy financiers living the good life while supporting al Qaeda in the shadows) maybe.

Thinking of al Qaeda as a system opens the door to deterrence by punishment. The various supporters and enablers of terrorism who are not eager to sacrifice their own lives for the cause can be threatened with retaliation for their role in facilitating terrorist operations. The threatened response need not be lethal, but could, depending on the actor, involve financial sanctions or imprisonment.

This approach is a good example of what Alexander George has described as "indirect deterrence." Traditionally, deterrent threats have been aimed directly at a potential attacker. Indirect deterrence, in contrast, is not aimed at attackers themselves, but at third parties whose actions could affect the likelihood that a potential attacker can or will carry out an assault. The likely need to pursue deterrence indirectly in countering terrorism was a major theme in a study conducted for the National Academy of Sciences soon after 9/11 and has been echoed in much of the subsequent research.

The indirect approach has an important implication. Just because a terrorist organization is a non-state actor, this does not mean states are irrelevant to deterrent calculations. If a terrorist group relies upon or benefits from some form of state assistance, then the state in question can be threatened with consequences if it does not cease providing support. Wyn Bowen has pointed out that threats to take action against state sponsors may be more a matter of "compellence" than deterrence. If a state is already supporting a terrorist group, the purpose of the threat is to get it to stop an activity already under way (compellence) rather than to prevent initiation of that activity (deterrence). The same logic applies to private supporters of terrorism as well. Since the conventional wisdom holds that compellence is harder to achieve than deterrence, Bowen cautions that it may be difficult to successfully coerce state sponsors to abandon their support for terrorism (though he concludes that it is still worth trying).

In addition, even failed compellence (for example, efforts after 9/11 to coerce the Taliban in Afghanistan to turn Osama bin Laden over to the United States) can have deterrent benefits if there is appropriate follow-up. In such cases, effective action to remove an offending regime from power (for example, the subsequent invasion of Afghanistan and removal of the Taliban government) can exercise a deterrent effect on other states. However, in efforts to deter other non-state actors rather than state sponsors, the fate of al Qaeda is more relevant. Elbridge Colby concludes that "deterrence requires that the United States take every step to destroy al Qaeda in order for our deterrent against terrorists to be credible."

This goal of destroying al Qaeda creates complications because, as Davis and Jenkins put it, "deterrence and eradication do not fit together easily." This reflects a famous observation by Thomas Schelling that deterrent threats only work if they are paired with an assurance that the threat will not be implemented if the other side complies. The U.S. intention to go after al Qaeda whether or not al Qaeda launches further attacks means there can be no U.S. promise to let the organization survive if it refrains from future terrorism. Without such an assurance, using deterrence by punishment against al Qaeda central is not possible. As noted above, though, threats of punishment might nonetheless work against elements of the network that enables al Qaeda. It is important to recognize that this will make assurances a necessity: to threaten private financiers or state sponsors with punishment if they support terrorism also requires promising to leave them be if they desist from aiding al Qaeda.

This insight is the basis for a proposal that in effect applies indirect deterrence to terrorist organizations rather than state or individual facilitators. Robert Trager and Dessislava Zagorcheva focus on deterring terrorist groups that are not affiliated with al Qaeda from allying with it. Some groups that share al Qaeda's ideology might be more concerned with local political struggles than with bin Laden's vision of global jihad. If so, Trager and Zagorcheva argue, their local goals can be held at risk. If the United States is willing to indicate that it will refrain from acting against local groups as long as they forgo assisting al Qaeda, it might deter them from doing so by threatening to intervene in their local struggles if they do assist al Qaeda. Trager and Zagorcheva's proposal is a logical extension of the indirect deterrence approach. Instead of focusing on deterring elements of al Qaeda's existing network, however, it seeks to prevent al Qaeda from expanding its reach. This analysis has an important policy implication. It suggests that former U.S. president George W. Bush made a mistake in declaring "a global war on terror." By suggesting the United States would go on the offensive against all terrorist groups in all regions, it gave them each an incentive to join together as allies facing a common threat. Trager and Zagorcheva also support their analysis with a case study of contrasting approaches utilized against two different insurgencies in the Philippines, making their article one of the few fourth-wave studies to actually test its theoretical ideas against empirical evidence.

Deterrence by Denial

The fact that many analysts do not see a viable way to use deterrence by punishment directly against al Qaeda has led much of the recent literature to focus instead on deterrence by denial. Davis and Jenkins identified two approaches, subsequently developed more fully by others, that fit this mode of deterrence. The first involves increasing the probability that individual attacks will fail. Davis and Jenkins observed that "even hardened terrorists dislike operational risk and may be deterred by uncertainty and risk." This means that homeland security measures and other steps taken to reduce the chances that terrorists can carry out spectacular attacks have deterrent effects. Terrorists "may be willing to risk or give their lives, but not in futile attacks. Thus, better defensive measures can help to deter or deflect, even if they are decidedly imperfect." Indeed, even before the Davis and Jenkins study appeared, a study conducted by Lawrence Livermore National Laboratory had also proposed that increasing the chances of operational failure could deter some terrorist attacks, and many subsequent studies have echoed this conclusion. Robert Anthony has provided empirical backing to the notion that anything that reduces the estimated probability of operational success could deter some behavior. Anthony notes that the 9/11 hijackers took multiple test trips on the same flights they later hijacked because they wanted to convince themselves that they would not be stopped before boarding on the day of the attacks. This suggests that successfully identifying and arresting one or more of the hijackers before 9/11 might have deterred the entire plot by increasing the perceived risk of failure.

As a second observation consistent with denial, Davis and Jenkins stressed the importance of illustrating that even successful terrorist attacks will not produce larger-scale effects on the United States. More recent work has come to see bolstering societal resilience as especially important. When a society can demonstrate the ability to withstand terrorism, it sends a message that using this tactic will not enable terrorist organizations to achieve their goals. Although Davis and Jenkins did not use the punishment and denial terminology in their work, other studies have invoked the distinction and argued that both approaches will be necessary to deter terrorism. Several analyses especially emphasize the second type of denial strategy discussed by Davis and Jenkins. They attach particular importance to showing that even successful attacks will not advance terrorists' overarching political goals. A report by a Student Task Force at the U.S. National War College (NWC) stressed that one way to deter terror groups is to ensure that there is "doubt placed in the terrorist's mind that even if acts of terrorism are successfully carried out, the overall aims may not be achieved." Some influential senior scholars have endorsed this idea as well, using it as a central argument to explain why they reject the premise that terrorism is undeterrable. Colin Gray, for example, claims that, despite the grandiosity of its objectives, al Qaeda "functions strategically" in trying to use its suicide attacks to advance those objectives. As a result, "it can be deterred by the fact and expectation of strategic failure."

A helpful framework for identifying different ways to use deterrence by denial against terrorism has been developed by James Smith and Brent Talbot. They observe that denial strategies can be implemented at the tactical, operational, and strategic levels. Efforts to improve homeland defenses and increase operational risk produce tactical deterrence. Smith and Talbot refer to this as "denial of opportunity." At the operational level, the goal is "denial of capability"—restricting access to resources terrorists require to conduct an ongoing campaign of attacks. Here, denial and punishment work in synergy. The indirect approach that threatens retaliation against third-party enablers can contribute to a direct version of denial by preventing terrorist organizations from getting the resources they need, such as money, weapons materials, and safe havens. Finally, at the strategic level, deterrence by denial involves the approach emphasized by the NWC Student Task Force, Gray, and others. Strategic deterrence by denial entails the "denial of objectives"—showing that terrorism will ultimately fail to help terrorist groups achieve their end goals.


Excerpted from Deterring Terrorism Copyright © 2012 by Board of Trustees of the Leland Stanford Junior University. Excerpted by permission of Stanford University Press. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents

Foreword Thomas C. Schelling vii

Acknowledgments ix

Notes on Contributors xi

Introduction: Linking Deterrence to Terrorism: Promises and Pitfalls Alex Wilner Andreas Wenger 3

Deterring Terrorism

1 Terrorism and the Fourth Wave in Deterrence Research Jeffrey W. Knopf 21

2 Deterring Terrorism, Not Terrorists Janice Gross Stein 46

3 Toward an Analytic Basis for Influence Strategy in Counterterrorism Paul K. Davis 67

4 Counter-Coercion, the Power of Failure, and the Practical Limits of Deterring Terrorism Frank Harvey Alex Wilner 95

Deterring WMD Terrorism

5 The Terrorist Perception of Nuclear Weapons and Its Implications for Deterrence Brian Michael Jenkins 117

6 Will Threats Deter Nuclear Terrorism? Martha Crenshaw 136

7 Strategic Analysis, WMD Terrorism, and Deterrence by Denial James M. Smith 159

8 Preventing Radiological Terrorism: Is There a Role for Deterrence? Wyn Q. Bowen Jasper Pandza 180

Empirical Evaluations

9 Deterrence of Palestinian Terrorism: The Israeli Experience Shmuel Bar 205

10 Turkish and Iranian Efforts to Deter Kurdish Insurgent Attacks David Romano 228

11 Mission Impossible? Influencing Iranian and Libyan Sponsorship of Terrorism Michael D. Cohen 251

12 A Toxic Cloud of Mystery: Lessons from Iraq for Deterring CBRN Terrorism Fred Wehling 273

Conclusion: Deterring Terrorism: Moving Forward Andreas Wenger Alex Wilner 301

Index 325

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