The history of terrorism is a history of well-known and historically significant individuals, entities, and incidents associated, whether rightly or wrongly, with terrorism. Scholars agree that terrorism is a disputed term, and very few of those labelled terrorists describe themselves as such. It is common for opponents in a violent conflict to describe the other side as terrorists. Those called terrorists can often be referred to as militants, paramilitaries, guerrillas, resistance movements or freedom fighters. However, they are united in the range of tactics they commonly employ which involves non-systemic covert or semi-covert warfare, driven by an ideological basis often political religious or socially based. They often seek to use propaganda of the deed to cause a psychological impact alongside the actions themselves to drive the aspired change.

Though many have been proposed, there is no consensus definition of the term “terrorism.” This in part derives from the fact that the term is politically and emotionally charged, “a word with intrinsically negative connotations that is generally applied to one’s enemies and opponents.” Listed below are some of the historically important understandings of terror and terrorism, and enacted but non-universal definitions of the term:

  • 1795. “Government intimidation during the Reign of Terror in France.” The general sense of “systematic use of terror as a policy” was first recorded in English in 1798.
  • 1916. Gustave LeBon: “Terrorization has always been employed by revolutionaries no less than by kings, as a means of impressing their enemies, and as an example to those who were doubtful about submitting to them….” 
  • 1937. League of Nations convention language: “All criminal acts directed against a State and intended or calculated to create a state of terror in the minds of particular persons or a group of persons or the general public.”
  • 1987. A definition proposed by Iran at an international Islamic conference on terrorism: “Terrorism is an act carried out to achieve an inhuman and corrupt(mufsid) objective, and involving [a] threat to security of any kind, and violation of rights acknowledged by religion and mankind.” 
  • 1988. A proposed academic consensus definition: “Terrorism is an anxiety-inspiring method of repeated violent action, employed by (semi-) clandestine individual, group or state actors, for idiosyncratic, criminal or political reasons, whereby – in contrast to assassination – the direct targets of violence are not the main targets. The immediate human victims of violence are generally chosen randomly (targets of opportunity) or selectively (representative or symbolic targets) from a target population, and serve as message generators.”
  • 1989. United States: premeditated, politically motivated violence perpetrated against noncombatant targets by sub-national groups or clandestine agents.
  • 1992. A definition proposed by Alex P. Schmid to the United Nations Crime Branch: “Act of Terrorism = Peacetime Equivalent of War Crime.”
  • 2002. European Union: “. . . given their nature or context, [acts which] may seriously damage a country or an international organisation where committed with the aim of seriously intimidating a population.”
  • 2003. India: Referencing Schmid’s 1992 proposal, the Supreme Court of India described terrorist acts as the “peacetime equivalents of war crimes.”
  • 2008. Carsten Bockstette, a German military officer serving at the George C. Marshall Center for European Security Studies, proposed the following definition: “political violence in an asymmetrical conflict that is designed to induce terror and psychic fear (sometimes indiscriminate) through the violentvictimization and destruction of 
  • noncombatant targets (sometimes iconic symbols).”