Why States Arm and Why, Sometimes, They Do So Together

Abstract Why do states arm? And why do they, sometimes, do so together with other states? International relations and security studies scholars have long explored the causes that propel states to arm. However, the extant literature has yet to provide a coherent theoretical framework to explain arms production and collaboration. Drawing from work in eclectic theorizing, this article contributes a systematizing, integrative perspective. States arm, and sometimes arm together with other states, for a variety of reasons, often with very diverse theoretical roots and origins; frequently, causes mix, mingle, and intertwine. Two case studies serve as building blocks for our eclectic theory, illustrating and buttressing our framework. A study of Brazil’s KC-390 military transport aircraft demonstrates the value of eclectic theorizing in explaining arms production. European (fragmented) collaboration to develop a sixth-generation fighter aircraft documents the benefits of applying an eclectic theory of arms collaboration augmented with a “domain of application” approach. That is, explanations rooted in particular theoretical traditions apply and play out strengths in specific domains, and may thus complement one another to generate comprehensive explanations. Among numerous other promising domain differentiations, we distinguish here between “high-end” and “low-end” arming. Our findings have important policy implications. If states’ arming, alone or with others, is multicausal, then no single policy alone will suffice to channel, control, limit, or reduce the proliferation of weapons.