How to Define Terrorism

How to Define Terrorism

By Joshua Sinai

Terrorist insurgencies, in all their configurations and local conflicts, constitute the primary warfare threat facing the international community. This is especially the case following September 2001, when al Qaida demonstrated that it had world class ambitions to inflict catastrophic damages on its adversaries. In other conflicts, such as the Palestinian-Israeli arena, terrorist rebellions are primarily localized. Because of the worldwide reach of al Qaida and its affiliates, including the spontaneous emergence of al Qaida-inspired groupings and cells in Western Europe, North America, and elsewhere, many nations have been upgrading their homeland security defenses and calling on their academic communities to provide analytical understanding of the nature and magnitude of the threat and how to counteract and resolve it. As a result, terrorism courses, research institutes and certificate programs have been proliferating at universities and other academic institutions around the world. Despite the great attention being devoted to terrorism studies; however, there is no consensus about the most fundamental starting point in terrorism studies: how to define terrorism.

Defining terrorism is the most ambiguous component in terrorism studies, with no universally accepted definition that differentiates attacks against civilian noncombatants or armed military or takes into account the latest trends in terrorist objectives and warfare. In 1983, the U.S. Department of State (DOS) formulated one of the most widely used definitions of terrorism. According to this definition, terrorism is "premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents, usually intended to influence an audience." [1] As part of this definition, the term "noncombatant" includes civilians and military personnel who are unarmed or not on duty. [2] The term 'international terrorism' refers to terrorism "involving citizens or the territory of more than one country," [3] while the term 'terrorist group' refers to "any group practicing, or that has significant subgroups that practice, international terrorism." [4]

The DOS's definition is operationally useful for legal reasons because it provides a legal basis to arrest and indict the perpetrators of such acts. However, at the analytical level, as mentioned above, there are no consensual definitions on what constitutes terrorism. Literature survey by a National Research Council (NRC) panel found there are no "precise general definitions of terrorism", but rather "a multiplicity of overlapping efforts, some more satisfactory than others, but none analytically sufficient." [5] Experts consider the term an "'essentially contested concept,' debatable at its core, indistinct around its edges, and simultaneously descriptive and pejorative." [6] To remedy this deficiency, the NRC formulated its own working definition, which includes the components of "(a) illegal use or threatened use of force or violence (b) with an intent to coerce societies or governments by inducing fear in their populations (c) typically with political and /or ideological motives and justifications and (d) an 'extra-societal' element, either 'outside' society in the case of domestic terrorism or 'foreign' in the case of international terrorism". [7] This definition has limited utility because other critical variables must be included. For example, in its February 2005 report on Combating Terrorism the National Science and Technology Council (NSTC) Subcommittee on the Social, Behavioral and Economic Sciences' argues that using the term 'terrorism' "may over-simplify different types of actors, warfare and motivations, encapsulating them in a single group or act so that critical variables are overlooked." [8] Here, the 'overlooked critical variables' include activities that fall below the threshold of violence, such as mobilizing support among a group's radical subculture, providing social welfare services, and even maintaining internet-based web sites.

Definitions of terrorism also vary as to whether terrorism includes attacks against only "noncombatant" targets (see DOS definition); or whether terrorism is also a tactic of warfare used by sub-national groups against all citizens of a state, whether civilian or military, including attacks against an "armed" military. This has analytical, statistical, and legal implications that need to be addressed and resolved. If terrorism is defined as attacks against only noncombatant targets, then attacks by groups that engage in terrorism against "armed" military targets should not be included, as they are in many cases, in terrorist incident chronology databases. [9] These attacks are military operations, and the perpetrators should be tried in military courts as guerrillas or armed combatants. Alternatively, terrorist attacks against armed targets might be counted separately as "guerrilla" incidents, as they are in the International Policy Institute for Counter-Terrorism's (ICT) terrorist incident chronology database. [11]

In general, guerrilla organizations employ "a combination of military and political methods intended to overthrow the government of a state" [11] while terrorist groups aim to provoke a harsh governmental response in response to their operations, which generally—but not always—take place "off battlefield." However, distinguishing these insurgent groups is not easy. For example, guerrilla organizations, such as the FARC in Colombia, also engage in terrorist tactics; and terrorist groups such as the Lebanese Hizballah and the Sri Lanken LTTE also consider themselves a guerrilla forces that control territory. Nevertheless, both terrorist groups and guerrilla forces engage in continuous warfare that characterizes their operations as a form of insurgency.

Two solutions have been offered to remedy the problem of counting as terrorism either attacks against noncombatant or combatant targets (which would characterize them as guerrilla forces). The first, by Alex Schmid, advocates using as a point of departure the consensus of what constitutes a "war crime", [12] Thus, "[i]f the core of war crimes—deliberate attacks on civilians, hostage taking and the killing of prisoners—is extended to peacetime, we could simply define acts of terrorism as 'peacetime equivalents of war crimes.'" [13] The second solution, by Boaz Ganor, defines terrorism as "a form of violent struggle in which violence is deliberately used against civilians in order to achieve political goals (nationalistic, socioeconomic, ideological, religious, etc.)." [14] He asserts that the use of 'deliberate' targeting of civilians in order to achieve political objectives is what distinguishes a terrorist act from guerrilla warfare, where military units are targeted. [15]

Ganor's formulation is important because it facilitates the outlawing of terrorism by the international community because all nations can agree that the deliberate targeting of civilians is unlawful and should be universally legislated as a crime, whereas attacks against military personnel would be considered part of regular warfare, including the right to militarily retaliate against those perpetrators. Ganor concludes that if acts of terrorism were universally outlawed as a form of warfare by the international community, then terrorist groups would have no choice but to "abandon terrorism and focus on guerrilla activity to achieve their political aims." [16] However, because terrorists are not "guerrilla" warriors, but seek "soft" targets which are easier to attack; they are unlikely to abandon such a tactic against civilians even if it provoked international condemnation.

Second, most definitions of terrorism used in the analytical community focus on the use of terrorism to "influence" or "coerce" the targeted audience by spreading fear beyond the localized incident throughout the wider society. [17] However, as demonstrated by the attacks of 9/11 in New York and Washington and 3/11 in Madrid, groups such as al Qaeda (and its affiliates) also intend to cause their adversaries massive human casualties and physical destruction. Thus, a new component in the definition might include the mass destruction component of terrorism, which is a manifestation of the latest trends in terrorist warfare.

Third, it is necessary not only to define terrorism, but state who may be a "terrorist." According to U.S. statutes, a terrorist group consists of two or more individuals that directly engage in terrorist-related violence (i.e., a combat unit), as well as:

  • Belonging to a supporting infrastructure whose activities contribute to violence in terms of:
    • Training
    • Planning
    • Fund raising (soliciting funds)
    • Logistics
    • Individuals who receive military training from terrorist groups
    • Individuals who "aspire" to commit violence in Internet chat rooms
    • Individuals who belong to political, social, or other groups that endorse or espouse terrorist activity
    • Individuals who endorse terrorist activity or persuade others to espouse such activity
      • Engage in incitement to violence (e.g., religious preachers)
    • Individuals who possess knowledge of an imminent operation by others but do not inform the authorities
  • Belonging to a terrorist group (or "loosely" affiliated); or
  • Being a "self-recruited" individual ("lone wolf") who engages in terrorist activities.

Finally, another definitional problem concerns counter-terrorism and homeland security. These terms are usually placed under the overall umbrella of combating terrorism, with anti-terrorism considered as largely defensive and "homeland security" oriented (e.g., involving law enforcement and judicial measures, as well as critical infrastructure protection), while counter-terrorism is viewed as the offensive (e.g, involving military and other "foreign" measures). However, the transnational nature of contemporary terrorism is leading to the blurring of the distinctions between defending national interests overseas and the "homeland," thereby necessitating a new conceptualization of counter-terrorism and homeland security.

To remedy these problem areas, a new definition of terrorism is hereby proposed: "Terrorism is a tactic of warfare involving premeditated, politically motivated violence perpetrated by subnational groups or clandestine agents against any citizen of a state, whether civilian or military, to influence, coerce, and, if possible, cause mass casualties and physical destruction upon their targets. Unlike guerrilla forces, terrorist groups are less capable of overthrowing their adversaries' governments than on inflicting discriminate or indiscriminate destruction that they hope will coerce them to change policy."

Hopefully, the new definition proposed in this article will spur new thinking by the analytical, policy, and operational communities involved in countering terrorism. Such thinking will bring to light the issues that should be considered in defining terrorism by individuals and groups against civilian and military targets and allow people to anticipate emerging trends in terrorist warfare. Understanding these issues at the analytical and policy levels will help to upgrade our anticipatory and preemptive operational capabilities to defeat the terrorist threat in all its current and future manifestations.

About the Author: Joshua Sinai is a Program Manager for Counterterrorism Studies at The Analysis Corporation, in McLean, VA.


[1] United States Department of State, Patterns of Global Terrorism 2003 (Washington, DC: Office of the Secretary of State, Office of the Coordinator for Counterterrorism, April 2004), p. xii.

[2] Ibid.

[3] Ibid.

[4] Ibid.

[5] Smelser and Mitchell, eds., Terrorism: Perspectives from the Behavioral and Social Sciences, p. 2.

[6] Ibid.

[7] Ibid.

[8] NSTC, Combating Terrorism: Research Priorities in the Social, Behavioral and Economic Sciences, p. 7.

[9]This argument is also made by the United Nations Office on Drugs and Crime: "If terrorism is defined strictly in terms of attacks on non-military targets, a number of attacks on military installations and soldiers' residences could not be included in the statistics" []. Interestingly, the MIPT Knowledge Base includes in its statistical data terrorist incidents against military targets, whereas the incident database compiled by the International Policy Institute for Counterterrorism (ICT), in Herzliya, Israel, differentiates between attacks against civilians, which it considers as "terrorist incidents," and attacks by terrorists against military targets, which it considers as "guerrilla incidents."

[10] See

[11] Ian F.W. Beckett, "Terrorism" in Encyclopedia of Guerrilla Warfare (New York: Checkmark Books, 2001), p. 231.

[12] United Nations Office on Drugs and Crime, "Definitions of Terrorism,"

[13] Ibid.

[14] Boaz Ganor, The Counter-Terrorism Puzzle: A Guide for Decision Makers (New Brunswick, NJ: Transaction Publishers, 2005), p. 17.

[15] Ibid., p. 20.

[16] Ibid., p. 24.

[17] Bruce Hoffman, "Terrorism," Microsoft® Encarta® Online Encyclopedia 2005 © 1997-2005.

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Perspectives on Terrorism is  a journal of the Terrorism Research Initiative and the Center for Terrorism and Security Studies

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