  The deterrent effect of military alliances is well documented and widely
accepted. However, such work has typically assumed that alliances are
exogenous. This is problematic as alliances may simultaneously influence the
probability of conflict and be influenced by the probability of conflict.
Failing to account for such endogeneity produces overly simplistic theories of
alliance politics and barriers to identifying the causal effect of alliances on
conflict. In this manuscript, I propose a solution to this theoretical and
empirical modeling challenge. Synthesizing theories of alliance formation and
the alliance-conflict relationship, I innovate an endogenous theory of
alliances and conflict. I then test this theory using innovative generalized
joint regression models that allow me to endogenize alliance formation on the
causal path to conflict. Once doing so, I ultimately find that alliances
neither deter nor provoke aggression. This has significant implications for our
understanding of interstate conflict and alliance politics.
