What is Terrorism?

The recent shootings in Kansas, as well as various events over the past few years involving individual acts of violence, have led people to ask why some of these events are considered to be merely crimes (homicides), some considered hate crimes, and others considered to be terrorism.  Anthony Lemieux engages this question directly over at Psychology Today in response to yesterday’s events.

Every semester that I teach International Relations, we spend a week dedicated to dissecting global terrorism (we spend longer on the issue when I teach Civil War and Terrorism as a full class) and we spend part of that time constructing a definition of terrorism within the class.  Ultimately, we do not settle on one class-wide definition of terrorism, but come up with several working versions for each individual within the classroom.  An end result with no clear answer is something that I actively encourage within the classroom as it reflects the nature of both politics and our academic understanding of the concept. As such, this post is about the implications of inclusion and exclusion in our definitions as opposed to advocating for any standard definition of terrorism.

I want my students to be good social scientists and part of that process involves both actively defining the phenomenon that we care about as well as sticking to those definitions throughout the course of a project.  As we are defining certain events that we want to study, we need to make sure that our definitions are clear, reasonable, and consistentwhether that definition is a definition of war, human rights, or terrorism.  Terrorism is  tricky word as, to borrow the old adage, one person’s terrorist is another’s freedom fighter. Additionally, there are hundreds of different definitions of terrorism.  Generally, those who define acts of “terror” as terrorism have a vested interest in making sure that their enemies are terrorists but the actors themselves are not.

"the state is the only terrorist"
 rUssEll shAw hIggs via Compfight

The definition of terrorism contains several binary exclusions/inclusions that vary from state to state, organization to organization, and researcher to researcher.  Whether to include or exclude particular groups or acts is a partly a question of function. As a social scientist, does your theory speak to a particular subset of violence or is it generalizable beyond a particular subset.  As a policymaker, how wide do you want your net to be in labeling groups?

To start discussing our binaries in defining terrorism, I will employ the START’s Global Terrorism  Database definition of terrorism (found in their codebook):

The GTD defines a terrorist attack as the threatened or actual use of illegal force and violence by a nonstate actor to attain a political, economic, religious or social goal through fear, coercion, or intimidation.

I have used the GTD for various projects in the past and this definition gives researchers access to thousands of terrorism events.  However, it defining the terms, it helps isolate things that we can include or exclude in our own definitions.


In defining terrorism, does the actor that commits the act matter?  In the GTD definition, they specify non-state actors which is not atypical, but it does clearly exclude at least one group (states).

Can states commit terrorism?  If we evaluate terrorism purely from the act and not the actor committing it, that is, evaluate the methods, targets, effects, and goals of the action, then certainly the state can commit terrorism.  While we have formalized legal institutions of what constitutes a legal versus an illegal use of force between states, those terms are loose and proponents of a given forceful action will claim legality while opponents of the actions will claim illegality. A couple examples are worth mentioning.  The firebombing of Germany by the British Royal Air Force during World War II was clearly designed to put pressure on civilian and domestic actors within Germany to compel the German government to end its campaign.  With the firebombing campaign comes the threat of future action and sustained costs on the military and civilians of Germany.

The “Shock and Awe” campaign of the United States against Iraq in 2003 clearly consisted of forceful actions intended to use fear and coercion to create political change in Iraq as well.  The legality of the US invasion of Iraq is certainly debatable, but between states, the legality of war does not seem to ultimately matter.  Thus, using the above definition, the only useful barrier to labeling this a terrorist action is that it excludes states.

There are two strong arguments to exclude states from our definitions of terrorism that warrant some discussion here: one methodological and another policy-based.  In terms of methodology, our theories that describe state actors may not describe non-state actors.  While some work disagrees on this point, it is a valid concern and, in terms of research, makes sense as a reason to include all actors.  Neorealism, for example, only describes the behavior of major powers and does not apply as well to non-major power actors within the system; it would make sense that if the theory is limited already, it may not be easily stretched to other actors.  In more general terms, we credibly have different expectations as to when a state may use terroristic violence than when a non-state may and that is reason enough for us to limit our social scientific definition.

From a policy or practical standpoint, we may exclude states if we have better or more specific types of crimes we can charge a state actor with.  For example, acts of state terrorism can be labeled as war crimes, crimes against humanity, crimes of aggression, genocide/democide, or by various other legalistic terms that compel specific sanctions that terrorism may not. If these charges carry more severe or specific weight, then using “terrorism” as a charge may make the term itself vague and muddy the policy implications.  Alternatively, a group charged with committing acts of terrorism may compel states to create specific legal and economic sanctions against the actor and applying it to states may be impractical (or just something a state actor is unwilling to do to a trade partner).

Other substate or semi-state actors may be worth lumping into the definition. Clandestine agents acting on behalf of the state can engage in terrorist acts. Since those actors are secretive, it will be impossible to discern whether they are a state or non-state actor during the course of the event. This obfuscation may last for years, decades, or be permanently etched into our history. For sake of data completeness, it may be worthwhile to include all such actors to ensure a stable database free from bias.  If a dataset loses points of data every time a state declassifies documents, then it is systematically biased by states that keep secrets better or longer (as an aside, this may create biases towards actions done by autocratic states if we expect democracies to be more transparent about their covert action in the long run).  Also, it is likely important to code data based on the immediate reaction and perspective of the time, especially if there is no evidence to suspect state involvement.  Finally, This delineation starts to get murky with state-sponsored terrorism or organized terrorismacts that may be funded or directed by a state, but conducted by non-state actors.

Beyond states, lone-wolf terrorism is worth discussing as well. While solitary actors may have larger political or social motives, whether their actions count as terrorism is debatable since the threat of future terrorist attacks are less likely.  Lone actors can certainly engage in terroristic shootings and bombings, but without organizational support, the act is isolated and does not represent a campaign of terrorism.  A campaign is something states and other actors can respond to, a random, isolated incident can be just that and does not warrant a response. For issues of theory-building, lone-wolf terrorism is fundamentally different than organized terrorism as it demands different responses by the state and it is likely caused by different factors.  Policy-wise, treating individual acts (i.e., going postal, suicide by cop, shooting spree, etc.), may offer different leverage and legal implications than if you treated it the same as organized terrorism.  One definition in the US code (22 USCS 2656f) excludes individual actors:

Premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents.

This definition certainly excludes individuals and draws a line between different types of actors.


Another binary choice in definition is whether the target matters.  Some definitions includes only civilian or primarily civilian targets while other definitions may include governmental agents.  The purpose of this delineation is partly to separate legitimate war targets from illegitimate non-military targets. If you exclude military targets as actions of war or war-like circumstances, you also need to provide further guidance of how you treat cases involving actors and property that enable the war fighting of the state.  Are only combatant targets legitimate or are particular kind of non-combatants also targets of military action? Are military bases non-terroristic targets?  Are command centers? Is the Pentagon? What part of the leadership is military and what part is not? The President of the United States is a civilian actor, but commands the military forces; are such actors military or terrorist targets?

Kosovo Flag (Official Flag) 17.02.2008
Creative Commons License Kosovo Future Maker via Compfight

Beyond the war capability of the state, are disarming the functions of the state legitimate or illegitimate targets (or legal or illegal)?  Again, such binary definitions need to include things from militarized police forces to seemingly benign state institutions like postal workers.  The Kosovo Liberation Army (KLA), a group that received funding and training from al-Qaeda, targeted police and postal workers for attacks seemingly to attempt provoke a massive over-reaction by the Yugoslav government. For many definitions of terrorism, the KLA is clearly a terrorist organization—and a very successful one at that: eventually, NATO intervened on behalf of the KLA against the Serbian government, it achieved autonomy, and many of its members entered politics and the Kosovo Protection Corps. US officials clearly stated that the KLA was a terrorist organization, but never actually legally labeled the group as such.

Even if we just excluded military targets in combat zones, there are still quite a few questions of legitimate versus illegitimate targets in war time and some normative war conventions suggest against targeted soldiers that are off-duty or otherwise prone and non-engage in active combat.

Beyond human targets, do attacks against property count as terrorism?  This is not entirely clearcut in all cases as some definitions suggest that there needs to be intended human costs while others embrace material costs.  Members of the Earth Liberation Front (ELF) have consistently been on the FBI’s list of most wanted terrorists for their involvement in violence against property.   Members of ELF have been known to commit arson against development projects, SUV lots, and other commercial enterprises with the intent to disrupt the activity of those businesses both directly and indirectly.  Using explosives and arson, the project immediately comes to a halt or is outright destroyed. Additionally, the cost to insure current and future projects increase immensely and can be prohibitive.  Likewise, the KKK burning a cross in someone’s home is designed to discourage social behavior such as members of a particular ethnic or racial group living in an area or discourage practices such as interracial marriage.   Thus, if we include violence against property to encourage change in social, economic, or political behavior, then these acts are clearly terrorism.  However, a broad definition that captures torching a lot filled with SUVs can also capture the Sons of Liberty dressing up in stereotypical American Indian garb, boarding the ships of the East India Company, and destroying their merchandise in the hopes to impose costs upon the company and encourage change to the Tea Act. If we think one act of violence is terrorism and another is not, then our definition should be clear in that regard.


Does terrorism actually have to include violence? Many definitions include just the threat of violence while other definitions require that future threats of violence must be at least implicit in the act itself.  Since terrorism is presumed to operate on fear, it is logical that the fear is over the possibility of future acts in addition to the anguish over present violence.  If we are coding events, or making criminal law, we need to decide if “terroristic threats” are terrorism.

Additional Definitions

The US has several operating definitions of terrorism depending on what law, bill, or organization defines it.  A few of those help to highlight the binary choices each one makes in determining what is and isn’t terrorism. The FBI offers two definitions; for international terrorism:

“International terrorism” means activities with the following three characteristics:

  • Involve violent acts or acts dangerous to human life that violate federal or state law;
  • Appear to be intended (i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and
  • Occur primarily outside the territorial jurisdiction of the U.S., or transcend national boundaries in terms of the means by which they are accomplished, the persons they appear intended to intimidate or coerce, or the locale in which their perpetrators operate or seek asylum.*

For Domestic Terrorism:

“Domestic terrorism” means activities with the following three characteristics:

  • Involve acts dangerous to human life that violate federal or state law;
  • Appear intended (i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination. or kidnapping; and
  • Occur primarily within the territorial jurisdiction of the U.S

In both cases, simple property damage is not enough, but there must be some implicit action that is dangerous to human life. Arson counts, dumping tea does not. The State Department makes the state versus non-state distinction:

(1) the term “international terrorism” means terrorism involving citizens or the territory of more than 1 country;

(2) the term “terrorism” means premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine agents;

(3) the term “terrorist group” means any group practicing, or which has significant subgroups which practice, international terrorism;

The ITERATE dataset, another important political science database that collects data on acts of international terrorism uses the following guidelines as established in its codebook:

The working definition of international/transnational terrorism used by the ITERATE project is the use, or threat of use, of anxiety-inducing, extra-normal violence
for political purposes by any individual or group, whether acting for or in opposition to established governmental authority, when such action is intended to influence the
attitudes and behavior of a target group wider than the immediate victims and when, through the nationality or foreign ties of its perpetrators, its location, the nature of its
institutional or human victims, or the mechanics of its resolution, its ramifications transcend national boundaries. International terrorism is such action when carried out by individuals or groups controlled by a sovereign state, whereas transnational terrorism is carried out by basically autonomous non-state actors, whether or not they enjoy
some degree of support from sympathetic states. “Victims” are those individuals who are directly harmed by the terrorist incident. While a given terrorist action may
somehow harm world stability, citizens of nations must feel a more direct loss than the weakening of such a collective good.


To conclude, I am not offering any particular new definition of terrorism, but instead wanted to discuss the implications of various existing definitions.  Some definitions are politically motivated while others are motivated by practical issues or theoretical implications.  As I tell my students in class, the definition you want to use depends on what your research is attempting to explain, what is feasible to study, and allows you to be consistent in your application.  Ultimately, when we define and operationalize any term, we must make choices; we must be able to defend those choices, recognize the impact of those choices, and be consistent in our labeling.

Michael A. Allen

About Michael A. Allen

Michael is an Assistant Professor in Political Science at Boise State University with a focus in International Relations, Comparative Politics, and Methodology (quantitative and formal). His work includes issues related to military basing abroad, asymmetric relations, cooperation, and conflict. He received his Ph.D from Binghamton University in 2011.

2 Replies to “What is Terrorism?”

  1. Pingback: What is Terrorism? | Dylan Kissane

  2. Pingback: Defining ‘terrorism’ | the learned mediator's blog

Leave a Reply