Terrorism

Terrorism generally refers to the deliberate use of violence or the threat of violence against civilians or other non-combatants to create fear and advance a political, religious, or ideological goal. Scholars broadly agree that no single definition of terrorism commands universal acceptance, partly because the term carries intrinsically negative connotations and is overwhelmingly applied to one’s enemies and opponents rather than to one’s own side, a pattern reflected in the common observation that almost no group or individual labeled a terrorist ever willingly adopts that description for itself.

Ancient and early historical roots

Historians disagree about how far back to trace the roots of terrorism, since the answer depends heavily on how broadly or narrowly the concept is defined. The Sicarii, a first-century Jewish group active in Roman-controlled Judaea, killed Jewish collaborators with Roman rule, often concealing daggers in crowds at religious festivals before striking, though some historians dispute whether this qualifies as terrorism in the modern sense of the term. The word terrorism itself is widely believed to originate from the Reign of Terror during the French Revolution of 1793 and 1794, when the ruling Jacobins used mass executions, including by guillotine, to intimidate political enemies, though some modern scholars decline to classify state violence of this kind as terrorism at all, reserving the term instead for non-state actors.

Nineteenth-century anarchism

The modern association between terrorism and non-state political violence developed significantly from the 1840s onward, as anarchist movements across Europe embraced what they called propaganda of the deed, using dramatic acts of violence, frequently involving dynamite, to inspire broader revolutionary uprisings among the working class. The Russian group Narodnaya Volya, active from 1878, pioneered the systematic targeted killing of government officials, most famously assassinating Tsar Alexander II in 1881, but the popular uprising its members expected to follow never materialized, and a sweeping government crackdown effectively destroyed the organization within a few years.

Twentieth-century expansion

Terrorism in the 20th century became closely associated with a wide range of political movements, including anarchist, socialist, fascist, and nationalist causes, with many of the nationalist examples tied directly to anti-colonial independence struggles against European empires. Some scholars classify the systematic state violence practiced by Nazi Germany and the Soviet Union under this broader heading as well, extending the concept beyond non-state actors to include governments terrorizing their own populations. Nationalist and anti-colonial groups including the Irish Republican Army, the Zionist militias Irgun and Lehi, and the Algerian National Liberation Front turned to bombings and targeted killings as part of broader independence campaigns, while a wave of left-wing groups active between the 1960s and 1980s, including Germany’s Red Army Faction, Italy’s Red Brigades, and the Japanese Red Army, pursued violent revolutionary goals within already-established Western democracies. Throughout the Cold War, both the United States and the Soviet Union also provided support to violent nationalist and insurgent groups as part of broader proxy conflicts, a pattern that complicates any simple narrative in which only designated enemies ever employed terrorist tactics.

Counterterrorism responses

Governments have responded to terrorism through a combination of law enforcement, military action, intelligence gathering, and increasingly, efforts to counter the ideological narratives that terrorist groups use to recruit new members. International cooperation has grown substantially since the September 11, 2001 attacks in the United States, including expanded intelligence sharing between allied governments, new domestic security legislation in many countries, and sustained military campaigns against groups such as al-Qaeda and later the Islamic State, though these responses have also drawn sustained criticism over their effects on civil liberties and due process.

Terrorism in the 21st century

The September 11, 2001 attacks on the United States, carried out by the al-Qaeda network, marked a decisive shift in how many governments understood and prioritized the terrorist threat, elevating transnational, religiously framed terrorism to the top of national security agendas across much of the world. The subsequent rise of the Islamic State in the 2010s introduced new tactics, including the extensive use of social media for recruitment and propaganda and the deliberate effort to hold and govern territory rather than operate purely as a clandestine underground movement, distinguishing it in important ways from earlier terrorist organizations that never attempted to control and administer populated territory. State sponsorship of terrorism, in which a government provides funding, weapons, training, or safe haven to a non-state militant group, has remained a persistent feature of the landscape, complicating counterterrorism efforts whenever the sponsoring state has the diplomatic or military weight to shield the group from direct retaliation.

FAQs

Why is there no single agreed-upon definition of terrorism?
Because the term carries strongly negative connotations and is applied almost exclusively to opponents and enemies, making a neutral, universally accepted definition difficult to establish.

Where does the word terrorism come from?
It is widely believed to originate from the Reign of Terror during the French Revolution of 1793 to 1794, when the Jacobins used mass executions to intimidate political enemies.

What was propaganda of the deed?
A 19th-century anarchist strategy of using dramatic violent acts, often involving dynamite, to inspire broader revolutionary uprisings among the working class.

Did state actors ever practice terrorism?
Some scholars classify the systematic violence of regimes such as Nazi Germany and the Soviet Union under this heading, though others reserve the term specifically for non-state actors.

What is state sponsorship of terrorism?
When a government provides funding, weapons, training, or safe haven to a non-state militant group, which can shield that group from direct retaliation if the sponsoring state has sufficient diplomatic or military weight.

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 2, 2026Researched and drafted with AI assistanceReport an issue