Terrorism, in its broadest sense, is the use of intentional violence to achieve political aims. The term is used in this regard primarily to refer to violence during peacetime or in the context of the war against non-combatants (mostly civilians and neutral military personnel).^[rx] The terms “terrorist” and “terrorism” originated during the French Revolution of the late 18th century^[rx] but became widely used internationally and gained worldwide attention in the 1970s during the Northern Ireland conflict, the Basque conflict, and the Israeli–Palestinian conflict. The increased use of suicide attacks from the 1980s onwards was typified by the 2001 September 11 attacks in the United States.

Types

The Task Force defines terrorism as “a tactic or technique by means of which a violent act or the threat thereof is used for the prime purpose of creating overwhelming fear for coercive purposes”. It classified disorders and terrorism into six categories:^[rx]

• Civil disorder – A form of collective violence interfering with the peace, security, and normal functioning of the community.
• Political terrorism – Violent criminal behavior designed primarily to generate fear in the community, or a substantial segment of it, for political purposes.
• Non-Political terrorism – Terrorism that is not aimed at political purposes but which exhibits “conscious design to create and maintain a high degree of fear for coercive purposes, but the end is individual or collective gain rather than the achievement of a political objective”.
• Anonymous terrorism – In the two decades prior to 2016-19, “fewer than half” of all terrorist attacks were either “claimed by their perpetrators or convincingly attributed by governments to specific terrorist groups”. A number of theories have been advanced as to why this has happened.^[rx]
• Quasi-terrorism – The activities incidental to the commission of crimes of violence that are similar in form and method to genuine terrorism but which nevertheless lack its essential ingredient. It is not the main purpose of the quasi-terrorists to induce terror in the immediate victim as in the case of genuine terrorism, but the quasi-terrorist uses the modalities and techniques of the genuine terrorist and produces similar consequences and reactions.^[rx][rx][rx] For example, the fleeing felon who takes hostages is a quasi-terrorist, whose methods are similar to those of the genuine terrorist but whose purposes are quite different.
• Limited political terrorism – Genuine political terrorism is characterized by a revolutionary approach; limited political terrorism refers to “acts of terrorism which are committed for ideological or political motives but which are not part of a concerted campaign to capture control of the state”.
• Official or state terrorism – “referring to nations whose rule is based upon fear and oppression that reach similar to terrorism or such proportions”. It may be referred to as Structural Terrorism defined broadly as terrorist acts carried out by governments in pursuit of political objectives, often as part of their foreign policy.

Other sources have defined the typology of terrorism in different ways, for example, broadly classifying it into domestic terrorism and international terrorism, or using categories such as vigilante terrorism or insurgent terrorism.^[rx] One way the typology of terrorism may be defined:^[rx][rx]

• Political terrorism
  • Sub-state terrorism
    • Social revolutionary terrorism
    • Nationalist-separatist terrorism
    • Religious extremist terrorism
      • Religious fundamentalist Terrorism
      • New religions terrorism
    • Right-wing terrorism
    • Left-wing terrorism
      • Communist terrorism
  • State-sponsored terrorism
  • Regime or state terrorism
• Criminal terrorism
• Pathological terrorism

Causes and motivations

Choice of terrorism as a tactic

Individuals and groups choose terrorism as a tactic because it can:

• Act as a form of asymmetric warfare in order to directly force a government to agree to demands
• Intimidate a group of people into capitulating to the demands in order to avoid future injury
• Get attention and thus political support for a cause
• Directly inspire more people to the cause (such as revolutionary acts) – propaganda of the deed
• Indirectly inspire more people to the cause by provoking a hostile response or over-reaction from enemies to the cause^[rx]

Attacks on “collaborators” are used to intimidate people from cooperating with the state in order to undermine state control. This strategy was used in Ireland, in Kenya, in Algeria, and in Cyprus during their independence struggles.^[rx]

Stated motives for the September 11 attacks included inspiring more fighters to join the cause of repelling the United States from Muslim countries with a successful high-profile attack. The attacks prompted some criticism from domestic and international observers regarding perceived injustices in U.S. foreign policy that provoked the attacks, but the larger practical effect was that the United States government declared a War on Terror that resulted in substantial military engagements in several Muslim-majority countries. Various commentators have inferred that al-Qaeda expected a military response, and welcomed it as a provocation that would result in more Muslims fighting the United States. Some commentators believe that the resulting anger and suspicion directed toward innocent Muslims living in Western countries and the indignities inflicted upon them by security forces and the general public also contributes to the radicalization of new recruits.^[rx] Despite criticism that the Iraqi government had no involvement with the September 11 attacks, Bush declared the 2003 invasion of Iraq to be part of the War on Terror. The resulting backlash and instability enabled the rise of the Islamic State of Iraq and the Levant and the temporary creation of an Islamic caliphate holding territory in Iraq and Syria until ISIL lost its territory through military defeats.

Attacks used to draw international attention to struggles that are otherwise unreported have included the Palestinian airplane hijackings in 1970 and the 1975 Dutch train hostage crisis.

Causes motivating terrorism

Specific political or social causes have included:

• Independence or separatist movements
• Irredentist movements
• Adoption of a particular political philosophy, such as socialism (left-wing terrorism), anarchism, or fascism (possibly through a coup or as an ideology of independence or separatist movement)
• Environmental protection (ecoterrorism)
• Supremacism of a particular group
  • Preventing a rival group from sharing or occupying a particular territory (such as by discouraging immigration or encouraging flight)
  • The subjugation of a particular population (such as the lynching of African Americans)
• Spread or dominance of a particular religion – religious terrorism
• Ending perceived government oppression
• Responding to a violent act (for example, tit-for-tat attacks in the Israeli–Palestinian conflict, in The Troubles in Northern Ireland, or Timothy McVeigh’s revenge for the Waco siege and Ruby Ridge incident)

Causes for right-wing terrorism have included white nationalism, ethnonationalism, fascism, anti-socialism, the anti-abortion movement, and tax resistance.

Sometimes terrorists on the same side fight for different reasons. For example, in the Chechen–Russian conflict secular Chechens using terrorist tactics fighting for national independence are allied with radical Islamist terrorists who have arrived from other countries.^[rx]

Personal and social factors

Various personal and social factors may influence the personal choice of whether to join a terrorist group or attempt an act of terror, including:

• Identity, including affiliation with a particular culture, ethnicity, or religion
• Previous exposure to violence
• Financial reward (for example, the Palestinian Authority Martyrs Fund)
• Mental health disorder
• Social isolation
• The perception that the cause responds to a profound injustice or indignity

A report conducted by Paul Gill, John Horgan, and Paige Deckert found that for “lone wolf” terrorists:^[rx]

• 43% were motivated by religious beliefs
• 32% had pre-existing mental health disorders, while many more are found to have mental health problems upon arrest
• At least 37% lived alone at the time of their event planning and/or execution, a further 26% lived with others, and no data were available for the remaining cases
• 40% were unemployed at the time of their arrest or terrorist event
• 19% subjectively experienced being disrespected by others
• 14% percent experienced being the victim of verbal or physical assault

Ariel Merari, a psychologist who has studied the psychological profiles of suicide terrorists since 1983 through media reports that contained biographical details, interviews with the suicides’ families, and interviews with jailed would-be suicide attackers, concluded that they were unlikely to be psychologically abnormal.^[rx] In comparison to economic theories of criminal behavior, Scott Atran found that suicide terrorists exhibit none of the socially dysfunctional attributes—such as fatherless, friendless, jobless situations—or suicidal symptoms. By which he means, they do not kill themselves simply out of hopelessness or a sense of ‘having nothing to lose.^[rx]

Abraham suggests that terrorist organizations do not select terrorism for its political effectiveness.^[rx] Individual terrorists tend to be motivated more by a desire for social solidarity with other members of their organization than by political platforms or strategic objectives, which are often murky and undefined.^[rx]

Michael Mousseau shows possible relationships between the type of economy within a country and the ideology associated with terrorism. Many terrorists have a history of domestic violence.^[rx]