Do Birds of a Feather Flock Together? Rebel Constituencies and Civil War Alliances

Abstract

Challenging influential perspectives that downplay the role of shared rebel constituencies, we
argue that they represent important causes of rebel alliances. Yet, we theorize distinct effects for
different types of constituency. While compatible political aspirations push both organizations
with a common ideological constituency and those with a common ethnic constituency to ally, for
co-ethnic organizations this cooperation-inducing effect is offset by a cooperation-suppressing
effect due to their higher risk of inter-rebel war. Leveraging a novel dataset of alliances in
multiparty civil wars (1946-2015), we find support for our theoretical expectations. Shared
ideological constituencies have a larger and more robust positive effect on the probability of
alliances than shared ethnic constituencies. Furthermore, we find that co-ethnic rebel organizations
tend to establish informal alliances only, while organizations sharing an ideological constituency
are drawn to formal alliances.

Keywords: Alliances, Civil Wars, Ideology, Ethnicity, Jihadism

JEL Classification: F50, C32, H89