Arming from Abroad: Arms Transfers and Interstate Military Conflict in the Interwar Period

What is the effect of arming on conflict? While a large literature debates this question, most existing research ignores that the majority of states are unable to arm themselves and must rely on arms transfers to acquire weapons. But even where studies investigate such external arming, existing findings are mixed: arming is found to either increase, decrease, or not affect the probability of conflict onset between states. In light of this, we present a theory of external arming that conceptualizes arms transfers not simply as material capability boosts, but also as carriers of information and as relational linkages to arms suppliers. We develop several hypotheses positing external arming and conflict to be linked both negatively and positively, depending on whether recipients gain new information from arms transfers and on the nature of the suppliers. Empirical tests using additive and multiplicative effects network models and data from the Interwar years, a historical period where our information-based theory of external arming is particularly applicable, provide support for these expectations. This research advances our under- standing of how arming affects interstate conflict, unifies the disparate findings reported in previous research on external arming, and highlights the importance of the relational in International Relations.