Their terror was directed against Jewish "collaborators", including temple priests, Sadducees, Herodians, and other wealthy elites.The term "terrorism" itself was originally used to describe the actions of the Jacobin Club during the "Reign of Terror" in the French Revolution. "Terror is nothing other than justice, prompt, severe, inflexible", said Jacobin leader Maximilien Robespierre. In 1795, Edmund Burke denounced the Jacobins for letting "thousands of those hell-hounds called Terrorists ... loose on the people" of France. In January 1858, Italian patriot Felice Orsini threw three bombs in an attempt to assassinate French Emperor Napoleon III. Eight bystanders were killed and 142 injured. The incident played a crucial role as an inspiration for the development of the early terrorist groups.Arguably the first organization to use modern terrorist techniques was the Irish Republican Brotherhood, founded in 1858 as a revolutionary Irish nationalist group that carried out attacks in England. The group initiated the Fenian dynamite campaign in 1881, one of the first modern terror campaigns. Instead of earlier forms of terrorism based on political assassination, this campaign used timed explosives with the express aim of sowing fear in the very heart of metropolitan Britain, in order to achieve political gains.Another early terrorist-type group was Narodnaya Volya, founded in Russia in 1878 as a revolutionary anarchist group inspired by Sergei Nechayev and "propaganda by the deed" theorist Carlo Pisacane.
A. J. Coady has written that the question of how to define terrorism is "irresolvable" because "its natural home is in polemical, ideological and propagandist contexts".Experts disagree about "whether terrorism is wrong by definition or just wrong as a matter of fact; they disagree about whether terrorism should be defined in terms of its aims, or its methods, or both, or neither; they disagree about whether states can perpetrate terrorism; they even disagree about the importance or otherwise of terror for a definition of terrorism." State terrorism
State terrorism refers to acts of terrorism conducted by a state against its own citizens or against another state. United Nations
In November 2004, a Secretary-General of the United Nations report described terrorism as any act "intended to cause death or serious bodily harm to civilians or non-combatants with the purpose of intimidating a population or compelling a government or an international organization to do or abstain from doing any act". The international community has been slow to formulate a universally agreed, legally binding definition of this crime. These difficulties arise from the fact that the term "terrorism" is politically and emotionally charged. In this regard, Angus Martyn, briefing the Australian parliament, stated,

The international community has never succeeded in developing an accepted comprehensive definition of terrorism. During the 1970s and 1980s, the United Nations attempts to define the term floundered mainly due to differences of opinion between various members about the use of violence in the context of conflicts over national liberation and self-determination.