International Center for the Study of Terrorism focuses latest research on improvised explosive devices

February 18, 2013

UNIVERSITY PARK, Pa. -- Examining the networks of people who create Improvised Explosive Devices, or IEDs, can provide important insights into the growing phenomenon of IED use by violent non-state actors around the world, according to researchers at the International Center for the Study of Terrorism (ICST) at Penn State.

“The IED is the signature tool of today’s insurgent,” explains John Horgan, ICST’s director. “Though most discussions about IEDs focus on their technical features, the development and diffusion of IEDs represent a type of ‘social activity.’ Even the simplest IED attack will involve multiple participants, each of whom plays a critical role in its development and execution. To be able to find new and creative ways to prevent and disrupt the IED process, we need to understand who is involved and what their roles entail.”

Researchers at ICST, in conjunction with partners at the State University of New York at Albany, American University and the University of Miami, recently concluded a three-and-a-half-year project examining 28 years of IED activity in Northern Ireland. The project, titled “From Bomb to Bomb-maker: A Social Network Analysis Model of the Socio-Psychological and Cultural Dynamics of the IED Process,” was the first systematic research effort on the IED process in Northern Ireland. Its other primary objective was to lay a solid foundation for further research on IED networks in Afghanistan and other operational theaters.

ICST interns developed a dataset of over 5,000 IED events and more than 1,200 terrorist actors in order to understand the social networks that produce and deploy IEDs. They focused on the Provisional Irish Republican Army, or PIRA, which is widely considered to have the greatest innovations and deepest expertise in IEDs by any non-state militant group. Between 1970 and 1998, the PIRA pioneered the systematic use of car bombs, created secondary devices like booby traps and developed new tactics to adapt to changing British counterterrorism policies.

“We examined the PIRA’s IED process from a multidisciplinary perspective,” said Paul Gill, former postdoctoral research fellow at ICST who served as the project manager. “By using insights from political science, industrial/organizational psychology, social network analysis and criminology, we were able to capture a more complete picture of the very intricate web of actors involved in the IED process, from engineers and technicians to bomb-planters and transporters.”

ICST found that a closer inspection of one of the PIRA’s most active units, the South Armagh Brigade, showed it to be structurally similar to contemporary jihadist groups. The analysis uncovered a much more decentralized network than expected, with multiple ties between individual actors as opposed to a hierarchical command-and-control structure. 

“The fact that the South Armagh Brigade and jihadist groups share similar structures may provide insight into how contemporary groups can be contained, countered and disrupted based on the United Kingdom’s past experience with the PIRA,” explained Gill.

The ICST-led research team also found patterns among PIRA members’ relationships with each other. “The terrorist network tended to cluster along three primary dimensions: brigade affiliation, whether the member participated in violent activities and the member’s specific role or task,” said Horgan.  “Individuals who engaged in violence were far more likely to connect with each other, and people who held a particular organizational role, such as IED constructor, IED planter or shooter, were far more likely to connect with individuals who held the same role than with members who fulfilled other roles.”

In another finding that may hold important implications for contemporary counterterrorism policies, researchers analyzed the impact of discriminate and indiscriminate killings by counterterrorism forces on IED usage and targeting. Contrary to what one would assume to be the desired results, researchers found that counterterrorism killings actually increased the number of PIRA IED attacks and particularly their attacks against civilians.

“The relationship between terrorist activities and counterterrorist operations suggests something of a ‘backlash’ or ‘boomerang’ effect, but this is an extremely complex issue that requires closer study,” said Gill.  “Our results do indicate, though, that the question of whether targeted killings ‘reduce terrorism’ is too simplistic given the secondary and even tertiary effects of such practices.”

According to Horgan, the results of their research indicate that terrorist networks are innovative organizations that will readily adapt to changing environments and increased counterterrorism policies.

“The IED problem is most certainly here to stay,” he said, “and the malevolent creativity with which they are developed must not be underestimated.”   

In addition to Horgan and Gill, other researchers who contributed to this study include Sam Hunter; James Piazza; Lily Cushenbery; Maj. Jeffrey Lovelace; Su Chuen Foo of Penn State; Victor Asal, Karl Rethemeyer, Ken Cousins and Ian Anderson of State University of New York at Albany; Joseph Young of American University; and Neil Johnson of University of Miami.

Support for this project came from the Office of Naval Research. 

Dedicated to the scientific study of terrorism and political violence, the International Center for the Study of Terrorism, based in the College of the Liberal Arts at Penn State, engages in research, teaching and training activities that are international in scope and multidisciplinary in nature. The center is committed to promoting and engaging in data-driven empirical research performed to the highest academic standards.

To learn more about ICST and the “Bomb to Bomb-maker” project, visit

For more information, or media inquiries, contact Kate Slavens, ICST research project manager, 325 Pond Laboratory, University Park, PA 16802, at 814-863-9550 or

  • A semi-automated network analysis of the Provisional Irish Republican Army’s South Armagh Brigade from 1970-1998

    A semi-automated network analysis of the Provisional Irish Republican Army’s South Armagh Brigade from 1970-1998. Each node represents an individual; the larger the node, the more network contacts the individual possessed.

    IMAGE: Penn State

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Last Updated March 04, 2013