We examine the history of the organization of the Irish Republican Army (IRA) and assess whether Republican terrorism reflected the possession of valuable group-specific human capital within the terrorist cell. The analysis is motivated by economic models of the formation of specialized groups. We also note the public-goods co-ordination problem facing terrorist groups, given their inability to use mainstream enforcement mechanisms. Of particular interest are four well-defined historical examples of factionalism within the IRA. The history of Irish republicanism is consistent with the prediction that increasing the opportunities for cell members outside of life in the organization, particularly through amnesty, destabilizes the organization but leaves a hardcore of remaining terrorists. The gap between terrorist characteristics and those belonging to members of wider society is more gradated than predicted.