Lethal Connections: The Determinants of Network Connections in the Provisional Irish Republican Army, 1970-1998

Using stochastic methods we illustrate that the Provisional Irish Republican Army's (PIRA) network is clustered along three primary dimensions: (a) brigade affiliation, (b) whether the member participated in violent activities, and (c) task/role within PIRA. While most brigades tended to foster connections within the brigade (that is, "closure"), the tendency to do so varied across the organization. Members who engaged with violent activities were far more likely to connect with each other; in later periods there is polarization into those who engage in violent activities and those who do not. Across brigades, those who engage in a particular task and role (improvised explosive device [IED] constructor, IED planter, gunman, robber/kidnapper/drug smuggler/hijacker) are more likely to connect with others who do the same task or play the same role than with other members who fulfill other roles. Standard forms of homophily (that is, the tendency to make connections with people who are similar in terms of demography or status) play a very weak role in explaining which members interact with one another. Finally, our analysis illustrates clear patterns of relational change that correspond to changes in the formal structures that PIRA's leadership promoted.