How Terrorism Spreads: Emulation and the Diffusion of Ethnic and Ethnoreligious Terrorism

• Published date: 01 November 2020
• DOI: 10.1177/0022002720930811
• Date: 01 November 2020
• Author: Sara M. T. Polo
• Subject Matter: Articles

Article

How Terrorism Spreads:

Emulation and the

Diffusion of Ethnic

and Ethnoreligious

Terrorism

Sara M. T. Polo

1

Abstract

Previous research on the causes of domestic terrorism has tended to focus on

domestic determinants. Although this approach can be helpful to understand many

causes of terrorism, it implicitly disregards how the tactical choices made by similar

nonstate actors elsewhere influence a group’s decision to resort to terrorist tactics.

This study argues that the adoption of terrorism among ethnic and ethnoreligious

groups results from a process of conditional emulation. Groups are more likely to

emulate the terrorist choice of others with whom they are connected by shared

political grievances and spatial networks. The theory is tested on a new and original

group-level data set of ethnic and ethnoreligious terrorism (1970 to 2009) using

geospatial analysis and spatial econometric models. The results provide strong

support for the hypothesized mechanism leading to the diffusion of terrorism and

suggest that emulation—more than domestic and contextual factors—substantially

influences dissidents’ tactic choice.

Keywords

terrorism, tactics, diffusion, emulation, spatial econometrics

1

Department of Government, University of Essex, Colchester, United Kingdom

Corresponding Author:

Sara M. T. Polo, Department of Government, University of Essex, Wivenhoe Park, Colchester CO4 3SQ,

United Kingdom.

Email: sara.polo@essex.ac.uk

Journal of Conflict Resolution

2020, Vol. 64(10) 1916-1942

ªThe Author(s) 2020

Article reuse guidelines:

sagepub.com/journals-permissions

DOI: 10.1177/0022002720930811

journals.sagepub.com/home/jcr

Recent terrorist attacks in Paris (2015) and Brussels (2016), carried out by returning

fighters from the war in Syria, have sparked fears of a spread of terrorism. Those

attacks showed how disenfranchised individuals could get inspired by the terrorist

activities of similar groups elsewhere, travel to conflict zones, receive training in

terrorist tactics, and conduct major attacks upon their return home (Schmidt 2016).

Indeed, terrorism has become an increasingly popular tactic among dissident groups.

Terrorist attacks have surged, globally, from an average of 1,523 attacks in the 1970s

to over 13,000 attacks in 2016 (Global Terrorism Database [GTD]). Moreover,

ethnic and ethnoreligious terrorism has become the most common: in 2016, four

of the five most active terrorist organizations were linked to ethnic and ethnoreli-

gious groups (i.e., Pashtun, Iraqi Sunni, Zaydi, and Kurds) killing an estimated 7,283

civilians. Despite the growing popularity of terrorism, however, not all groups

engage in this tactic. The tactical choices of the above groups stand in contrast with

those of other ethnic groups fighting conflicts in Chad, Myanmar, Liberia, and

Ethiopia, who largely avoided resorting to terrorism. Why has terrorism become a

dominant tactic among some groups and not others? To what extent are the Paris and

Brussels attacks illustrative of a broader phenomenon, whereby a group’s choice to

adopt (or reject) terrorism is influenced by the tactical choices of similar groups

elsewhere?

Despite a wealth of research on the causes of terrorism, existing work has not yet

adequately addressed the choice of terrorism by specific subnational groups and

organizations. Quantitative studies of domestic terrori sm

1

typically focus on the

attributes of states where terrorism emerges. Yet, this approach does not explain

why countries that are similar in many aspects (e.g., regime type, institutions, eco-

nomic wealth, instability) experience very different levels of terrorism by ethnic and

ethnoreligious groups, or why such terrorism has become so widespread. While it

may be tempting to explain domestic terrorism based solely on attributes of the

domestic context, this approach is incomplete as it disregards strategic interdepen-

dence in nonstate actors’ decision-making; that is, how the tactical choices by one

group affect the choices of other groups elsewhere. To date, only a handful of studies

have examined the diffusion of terrorism, but focusing only on transnational terror-

ism and on the country-level incidence of attacks (e.g., Braithwaite and Li 2007;

Neumayer and Plu

¨mper 2010). Domestic terrorism, however, is not a countrywide

phenomenon but typically emerges from specific subnational communities (Nemeth,

Mauslein, and Stapley 2014). Thus, we still know little about why terrorism is

chosen by some substate groups and not others and under what conditions domestic

groups respond to external incentives and “copy” the terrorist choice of others.

This article aims to fill this gap. I present a novel argument focusing on domestic

terrorism as the product of a diffusion process whereby groups observe and emulate

the tactical choice of others whom they perceive as similar to them and as an

example for their own behavior. The tactical choices and experiences of similar

ethnic groups are perceived to (and in fact may) contain relevant information on

the appropriateness of a tactical innovation in a specific political context (Simmons

Polo 1917