A Department of Homeland Security Center of Excellence led by the University of Maryland

Understanding and Combating Mass Casualty Terrorism (MCT)

Understanding and Combating Mass Casualty Terrorism (MCT)

Other START Researchers: 
Sarah SpaldingMila Johns

Project Details


This study consisted of three components: (1) Comparative case studies of groups that have engaged in mass-casualty terrorism (MCT), focused on the decision processes involved in the selection of a mass casualty attack from the wide range of attack options open to terrorists, and (2) systematic collection of country-level, organizational-level and individual-level data on MCT events. These data will supplement START's existing GTD, and provided the materials necessary for (3) statistical analyses focused on understanding the methods and target selection of MCT.

Primary Findings: 

This research project generated both theoretical and empirical findings, as detailed below.

Theoretical Findings:

1. The psychology of mass violence remains an underexposed area of study, despite a surge in interest in the past decade.

2. A comprehensive review of both the theoretical and empirical literature revealed that, while there are strong disincentives for most terrorists to engage in mass casualty terrorism (MCT), there are also a host of incentives.

3. To obtain greater theoretical granularity, a unified field theory of mass violence was formulated on the basis of field theoretic principles: Four mutually interacting layers were identified and represented in a circle structure. The outer layer of circles comprises those variables that pertain to macro-economic and societal factors. The variables in this layer include economic instability, cultural characteristics such as cultures of violence, of superiority, of acceptance, and of devaluation, and ideological notions of collective trauma, of antagonism, of dominance, and of sublime technology. Encapsulated within the outer layer, one finds the layer of community level indicators. These include segregation, in-group homogeneity, and limited minority influence. Furthermore, this level includes a strong within role differentiation, aggressive role models, and a general approval of violence. Within the community layer is the layer of the immediate social situation. Relevant at this level are the presence of an authority instructing to use violence, the presence of violence, and salient social identity and group norms conducive to violence. Within the immediate social situation is the personal level. Indicators on this level include fear and insecurity, closed-mindedness, dominance, and a need for validation. Unified field theory also suggests more proximal causes, which include prejudiced social perceptions and dehumanization, and include emotions such as anger, disgust, contempt, and hate. Moreover, personal beliefs may constrain and facilitate mass violence. These beliefs include just-cause beliefs, the belief one is acting on behalf of the group, the belief a situation is threatening, and perception of victimhood. Finally, mass violence is assumed to increase in likelihood through training, gradual reinforcement of violence, and repetitive involvement in violence.

Empirical Findings:

1. MCT attacks inflict a dramatically disproportionate number of casualties relative to their percentage of total terrorist attacks. So, aside from their often spectacular nature, preventing MCT attacks offers a large "payoff" in terms of lives saved and injuries avoided and thus warrant substantial counterterrorism resources and attention. While mass casualty attacks have recently risen in frequency, neither mass casualty nor mass fatality attacks are a recent phenomenon -- there have been many such attacks throughout the past four decades, and casualty and fatality rates from these attacks are in general no higher today than in several other periods over the past forty years. Moreover, mass casualty terrorism is not a Western problem -- in fact developing nations have experienced the brunt of MCT.

2. The empirical record emphasizes that 9/11 was not an aberration -- for terrorists to kill large numbers of people, they do not necessarily have to acquire high-tech weaponry or develop Bondian plots. Once a minimal level of organizational cohesion and capability has been reached, even relatively crude weapons and unsophisticated attack methods suffice to create mass carnage. This is amply illustrated by the observation that while bombs are the weapon of choice for MCT, mass fatality attacks have more often been carried out with the ubiquitous gun.

3. CBRN terrorism and MCT hardly overlap, at least not thus far. So, while CBRN terrorism and the potential for weapons of mass destruction (WMD) use by terrorists (which in essence would occur at the nexus of CBRN and MCT) are valid security concerns -- particularly in light of advances in technology and the growing technical skills evidenced by terrorists -- at least as much policy (and scholarly) attention should remain focused on the more mundane conventional MCT threats.

4. The data also highlight the asymmetric nature of terrorism and bring home the difficulty of preventing MCT at the tactical level, since most attacks do not involve large attack teams numbering in the dozens. Instead, most MCT attacks are carried out by small groups of attackers (albeit often supported by a much larger logistical tail), with many attacks that kill more than 100 people involving only a single attacker at the point of attack.

5. Perhaps most importantly, there is no simple profile of a mass casualty terrorist; past perpetrators have been as varied as leftist groups in Latin America, obscure religious cults in Japan and the United States, and ethnonationalist movements in Africa. However, the analysis has suggested several characteristics that might indicate a greater proclivity for engaging in MCT. Most importantly, terrorist organizations connected to multiple partners, that have extensive experience with violent attacks, control territory, are based in a non-democratic country and/or who imbue their ideologies with religious elements should attract enhanced counterterrorist attention.

6. The National Union for the Total Independence of Angola (UNITA) emerged as a statistical outlier (false negative) from the quantitative model. A close case study of this organization's mass-casualty attacks and the antecedents thereof revealed that in the instances of MCT examined, the intent of the attacks was to communicate UNITA's continued political relevance to the Angolan government, as well as its state allies and opponents. The high numbers of casualties sought were thus more strategically symbolic than instrumental or ideologically motivated, and were designed as a means to deliver UNITA's message to various audiences in a manner that could not be ignored.


Researchers adopted a multi-method approach. The team first completed a review of the literature on mass-casualty terrorism, as well as a comprehensive survey of the psychology of mass violence, including identifying theoretical strands at multiple levels of human activity as well as assessing existing empirical support for these theories. Using the Global Terrorism Database as a springboard, researchers constructed a robust Mass Casualty Incident Database, which captured several event-level variables related to MCT. The researchers then developed and analyzed a regression model of organizational resort to MCT. Finally, the team conducted three in-depth case studies of the factors affecting the decision to engage in MCT: UNITA, ETA, and al-Qa'ida.


Project Period: 
June 2008 to December 2011