In our overview of terrorism, we try to understand how the number of terrorist acts varies around the world and how it has changed over time. To do this, we need a clear and consistent definition of what terrorism is, and how it’s different from any other form of violence. This is not straightforward.
Terrorism is defined in the Oxford Dictionary as “the unlawful use of violence and intimidation, especially against civilians, in the pursuit of political aims.” We quickly see that this definition is unspecific and subjective.1 The issue of subjectivity in this case means that there is no internationally recognised legal definition of terrorism. Despite considerable discussion, the formation of a comprehensive convention against international terrorism by the United Nations has always been impeded by the lack of consensus on a definition.2
The key problem is that terrorism is difficult to distinguish from other forms of political violence and violent crime, such as state-based armed conflict, non-state conflict, one-sided violence, hate crime, and homicide. The lines between these different forms of violence are often blurry. Here, we take a look at standard criteria of what constitutes terrorism, as well as how it might be distinguished from other forms of violence
The criteria for terrorism
Violent actions are usually categorised according to the perpetrator, the victim, the method, and the purpose.3 Different definitions emphasise different characteristics, depending on the priorities of the agency involved.
In our coverage of terrorism, we rely strongly on data from the Global Terrorism Database (GTD), which defines terrorism as “acts of violence by non-state actors, perpetrated against civilian populations, intended to cause fear, in order to achieve a political objective.”4,5 Its definition excludes violence initiated by governments (state terrorism) and open combat between opposing armed forces, even if they’re non-state actors. In our definitions section we provide the GTD’s more detailed definition, in addition to others such as that of the United Nations.
A few key distinguishing factors are common to most definitions of terrorism, with minor variations. The following criteria are adapted from the definition given by Bruce Hoffman in Inside Terrorism.6
To be considered an act of terrorism, an action must be violent, or threaten violence. As such, political dissent, activism, and nonviolent resistance do not constitute terrorism. There are, however, many instances around the world of authorities restricting individuals’ freedom of expression under the pretext of counter-terrorism measures. Human rights groups, such as Amnesty International and Human Rights Watch, publish reports on such cases of censorship.
The inclusion of damage to private and public property in the definition of terrorism is a point of contention, but it is generally accepted in legal and statistical contexts.
An action must also be carried out for political, economic, religious, or social purposes to count as terrorism. For example, the terrorist organisation Islamic State of Iraq and the Levant (ISIL) has clearly stated its political goal to establish itself as a caliphate. Likewise, attacks perpetrated by white extremists have discernable sociopolitical motivations, and so are considered acts of terrorism. By contrast, violent acts committed without a political, economic, religious or social goal are not classified as terrorism, but instead as ‘violent crimes’
To be classified as terrorism, actions must be designed to have far-reaching psychological repercussions beyond the immediate victim or target. In other words, an action must aim to create terror through “its shocking brutality, lack of discrimination, dramatic or symbolic quality and disregard of the rules of warfare”.7
Additionally, targetting noncombatant, neutral, or randomly chosen people – generally, people not engaged in hostilities – is a necessary but not sufficient condition to constitute terrorism. The US State Department includes in the definition of ‘noncombatant’, “military personnel who at the time of the incident are unarmed and/or not on duty.” They “also consider as acts of terrorism attacks on military installations or on armed military personnel when a state of military hostilities does not exist at the site.”8 As such, actions during open combat, where a state of military hostility exists, do not constitute terrorism.
Terrorist actions must be also conducted either by an organization with an identifiable chain of command or conspiratorial cell structure (whose members wear no uniform or identifying insignia), or by individuals or a small collection of individuals directly influenced by the logical aims or example of some existent terrorist movement and its leaders (typically referred to as a ‘lone wolf’ attack).
Finally, the action must be perpetrated by a subnational group or non-state entity. Equivalent actions perpetrated by the armed forces of nation states are given different classifications, such as ‘war crime’ or one-sided violence.
Distinguishing terrorism from other forms of violence
Based on the criteria above, we can begin to separate terrorism from other types of violence based on some very simplified distinctions:
killings perpetrated by non-state actors against civilians, which are not ideological in nature i.e. not motivated by a particular political, economic or social goal, are classified as homicide;
Violence perpetrated by non-state actors against civilians, specifically based on ethnicity, sexuality, gender, or disability, without political or social intent to cause widespread fear, is classified as a hate crime;
violence involving open combat between opposing armed forces is classified as state-based armed conflict, if at least one of the parties is the government of a state;
if, in the scenario above, none of the parties is the government of a state, this is classified as a non-state conflict;
violence perpetrated by governments against civilians is classified as one-sided violence.9
How terrorism and other forms of violence overlap
But even with these distinctions in mind, there is not always a clear-cut boundary between terrorism and other forms of conflict like civil war and violence targeting civilians.
The GTD codebook notes this: “there is often definitional overlap between terrorism and other forms of crime and political violence, such as insurgency, hate crime, and organized crime”. Given the difficulty of excluding such cases in a systematic way, this database includes them wherever they meet the basic criteria that form the definition of terrorism. However, it also flags up instances where the coders had doubts whether the event would be better characterised by one of these ‘alternative designations’. You can explore this by downloading the full GTD dataset at their website. As such, there is a partial overlap between common definitions of terrorism and certain other types of conflict.
Another way in which conflict researchers distinguish between different types of violent acts is in terms of the number of victims. The Uppsalla Conflict Data Program (UCDP), for instance, only includes events involving at least 25 deaths – a requirement not present in GTD. Therefore many, but not all, of the events recorded in GTD will also be counted in the UCDP data, which are the basis of our charts of non-state and one-sided violence.
As an example, the September 11 attacks on the World Trade Centre in New York City are included as both a terrorist attack in the GTD, and an episode of one-sided violence in the UCDP data, because the perpetrators were members of the organised group Al-Qaida, and it resulted in more than 25 deaths. However, the Norway attacks on 22 July 2011, in which a right-wing extremist killed or injured more than 100 people, is included in GTD as a terror attack, but is not present in UCDP data, since the attacker was acting independently, and did not represent the government of a state.
We are therefore aware that there can be overlap between the data we present on terrorism and that which we present on conflict. This fact is a crucial point in understanding the definition of terrorism and what the term means to people. Many of the terrorist attacks that take place today are events which many people would think of as a different form of violence or conflict. In fact, most terrorism actually happens in countries of high internal conflict, because ultimately terrorism is another form of conflict.
Global Terrorism By Graphs