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How to Study Terrorism

By Dr. Joshua Sinai

Terrorist insurgencies, whether by groups or radicalized lone actors, constitute one of the primary national threats facing the United States and the international community. Additionally, with heightened political polarization in American society, with militant groups also protesting against or in favor of a host of issues such as lockdown restrictions to contain the COVID-19 pandemic (including potential resistance by some to being vaccinated), law enforcement reform, and the perceived legitimacy of election results, there is an escalation of communicated and physical threats against public officials, with many of them now being protected by 24/7 security details.

Cyber threats are considered one of the top threats facing the U.S. critical infrastructure’s sectors and sub-sectors, with a range of cyber-attacks and breaches against them. These cyber threats also have a terrorist component. Terrorist groups of all extremist ideological orientations already use the internet, including the ‘Dark Web’, to spread their propaganda, radicalize and recruit new adherents, communicate with one another, raise funds, as well as launch cyber-attacks against their state adversaries’ digital infrastructures, whether through hacking or other methods.            

While the subject of terrorism and countering terrorism is extensively studied at universities around the world, with dozens of new books and hundreds of articles on these topics published every year, there are numerous areas where the academic discipline needs to improve. This article, on how to define terrorism, is the first in a series that will examine these issues and propose remedies, including proposing best practices to teach these issues at universities.

Defining Terrorism

The most important issue in terrorism studies is how to define terrorism, especially because of the widespread confusion about how to define it. The first requirement is to place terrorism, which is a form of military warfare, within the overall context of warfare that consists, at one end of a continuum, as regular warfare (i.e., between adversarial conventional military forces in a battlefield) and, at the other end of the continuum, irregular warfare, which consists of paramilitary (i.e., guerrilla) and terrorist formations that are challenging their adversary states. As a proposed best practice in studying this issue, my university is introducing a new course on the history of military warfare that will cover all of these issues, to enable students to understand where terrorism (and guerrilla formations) fit in to overall warfare as it has been practiced over the centuries, including today.

A second requirement in defining terrorism is to explain what exactly does it constitute. The ‘conventional’ definition regards terrorism as the deliberate use of politically motivated violence by sub-state groups against civilian noncombatants in order to coerce their government adversaries to cave in to their objectives and demands. One reason for this definition is that terrorism can be codified in a country’s criminal justice laws, and by intentionally targeting civilians, such terrorist perpetrators, if they survive their attacks and are arrested, can then be tried in civilian courts, so there is some justification for this definition.

Numerous terrorist attacks, however, have deliberately targeted armed combatants, particularly military personnel and their facilities. Armed law enforcement personnel and their facilities are also targeted by terrorists, but in this article, the focus is on attacking the military.

In fact, targeting armed combatants and their facilities is a prized target for terrorists because it places them at the same “battle” level playing field as their military adversaries. In a discrepancy that needs to be resolved, therefore, according to the ‘conventional’ definition of terrorism, are attackers against military targets not considered as terrorists, even if they belong to what is officially designated as a terrorist organization?

Significant examples of terrorists attacking the armed military include the following:

  • October 23, 1983: A suicide truck bombing by a Hizballah operative of the Marine Corps barracks in Beirut (resulting in the deaths of 220 Marines and 21 other service personnel),
  • October 12, 2000: A small vessel suicide bombing by two al Qaida operatives of the USS Cole, a guided missile destroyer, that was docked at the Yemeni port of Aden (resulting in the deaths of 15 sailors and wounding 37 others).  
  • September 11, 2001:  Flight77, one of the four airline flights hijacked by al Qaida operatives, originating at Dulles International Airport, crashed into the side of the Pentagon, in Arlington, VA, killing 125 personnel (55 military personnel and 70 civilians working for the defense department). The aircraft’s 53 passengers and 6 crew were killed, along with the five hijackers.
  • November 5, 2009:  A U.S. Army Major, a psychiatrist who was a radicalized into al Qaida’ inspired violent extremism, carried out a mass shooting attack at his base at Fort Hood, near Killeen, Texas, killing 13 soldiers and wounding more than 30 others.

As demonstrated by these and numerous other incidents in which terrorists have attacked the military, this category of terrorism can’t be dismissed from the overall definition of terrorism.

This isn’t merely a problematic definitional issue. It affects how software-based terrorist incident databases are coded and populated. Such incident databases are intended to provide trends about the magnitude of terrorist threats facing countries and globally. Only coding attacks against noncombatant targets, in order to adhere to the ‘conventional’ definition of terrorism, but not against the armed military (and also armed law enforcement personnel and facilities), results in severely undercounting the number of overall terrorism incidents worldwide.

Another problem with terrorist incident databases is that, for various reasons, they don’t account for disrupted plots and attacks underway that are prevented, so the full quantifiable picture of a terrorist threat facing a country is not provided.

A further problem in defining terrorism is the emphasis by some academic writers that the primary objective of terrorists is to inflict psychological damage on their adversaries, but not to necessarily inflict mass fatalities and physical damage by their attacks. Again, it is true that one of the objectives of terrorist attacks is to inflict psychological damage on their targeted populations by spreading fear and anxiety among the targeted population that a localized attack is not only affecting the victims, but that such attacks can occur anywhere else in society, so no one is completely safe from their terrorist adversary. In my view, however, the psychological component of terrorist attacks is a secondary and collateral objective of such attacks, with the primary objective still to inflict as many mass casualties and physical damage as possible, since terrorists, like other non-political violent assailants, are still basically murderers, not legitimate political actors, as such.

To resolve such cognitive dissonance in the discipline over the definition of terrorism, in a 2008 article I proposed the following definition, which I believe is still relevant today: "Terrorism is a tactic of warfare involving premeditated, politically motivated violence perpetrated by subnational groups or clandestine agents against any citizen of a state, whether civilian or military, to influence, coerce, and, if possible, cause mass casualties and physical destruction upon their targets. Unlike guerrilla forces, terrorist groups are less capable of overthrowing their adversaries' governments than on inflicting discriminate or indiscriminate destruction that they hope will coerce them to change policy."1

I hope this article’s discussion on how to study the definition of terrorism is of interest in advancing further understanding of these issues.

In my next series of articles, additional issues in terrorism and counterterrorism studies will be discussed.


1. Joshua Sinai, “How to Define Terrorism,” Perspectives on Terrorism, Vol. 2, No. 4, February 2008, pages 9-11. Retrieved from

Dr. Joshua Sinai is a Professor of Practice, Counterterrorism Studies, at Capitol Technology University. His more than 30-year career in Washington, DC, has included working as a contractor at the Department of Homeland Security’s National Operations Center (when it was first stood up) and DHS’s Science & Technology Directorate, as well as at the FBI’s Foreign Terrorist Tracking Force (FTTTF) and the Federal Protective Service’s (FPS) Training Branch. He also serves as Book Reviews Editor of the online bi-monthly academic journal “Perspectives on Terrorism,” for which he writes the “Counterterrorism Bookshelf” review column