Replication Data for: Crowding Out the Field: External Support to Insurgents and the Intensity of Inter-rebel Fighting in Civil Wars

How does external support to insurgents influence the likelihood that the latter will get involved in violent clashes against other rebel groups? In this article, we outline a theoretical framework which contends that, in multiparty civil wars, rebels sponsored by foreign states are more likely to participate in high-intensity inter-rebel conflicts than rebels receiving no support from external states. We argue that this is because external support creates strategic incentives for insurgent leaders to target other rebel contenders in order to signal resolve to their sponsors and to crowd out the battlefield ahead of the post-conflict period. External support, moreover, tends to activate potent socio-psychological mechanisms among rank-and-file combatants that may remove restraints on the use of violence against other rebel fighters. Using data on inter-rebel conflicts from 1989 to 2018, we test these hypotheses with a set of large-N regressions and find strong support for our theory. Further analyzes inductively reveal that our statistical results are likely, to some extent, to be driven by the prevalence of religious insurgencies in contemporary conflicts. Religious insurgencies display organizational features that could reinforce vertical strategic incentives and horizontal socio-psychological dynamics, thereby increasing their involvement in inter-rebel fighting. To further probe the ‘meso-foundations’ of inter- rebel fighting following rebel sponsorship, we then provide qualitative evidence on the Syrian Civil War. Our article contributes to scholarship by highlighting the consequences of external support on conflict processes beyond the insurgent-incumbent dyad.