Do arms sales cause war? Or do wars cause arms sales? Critics of arms sales often argue that selling weapons abroad fuels conflict. And indeed, one can point to one or more sides using American weapons in many recent conflicts including Syria, Yemen, and Iraq. Skeptics argue, on the other hand, that weapons don’t start the fire and that conflicts would arise whether or arms exporters like the United States sell weapons abroad.

The debate has important implications for foreign policy. If selling or transferring weapons abroad makes conflict more likely, or intensifies conflicts already in process, then the United States should rethink its long‐​held policy of selling weapons to pretty much any nation that wants them. If, on the other hand, arms sales have no impact on conflict or make conflict less likely, then the Trump administration’s intention of expanding arms sales should be seen as a positive move.

As it turns out, several academic studies have looked at this question. The primary conclusion of these works is that although arms sales do not create conflicts out of thin air, they do make conflict more likely when the conditions for conflict are already present.

The basic logic behind this conclusion is fairly straightforward and has been noted in the academic literature for some time. In a 1998 article, “Arms Transfer Dependence and Foreign Policy Conflict,” David Kinsella argues that states that enjoy a steady flow of arms – especially from multiple countries – tend to pursue more aggressive foreign policies. The increase in the recipient’s military capability makes victory in a potential conflict more likely, which in turn raises the likelihood that the state will start disputes, demand concessions from its neighbors in those disputes, and to escalate to conflict if negotiations fail to produce the desired outcome. Using case studies from Israel, Egypt, Syria, Iran, Iraq, India, Pakistan, Ethiopia, and Somalia Kinsella finds that, when a country has more than one weapons supplier, arms sales drastically increase the chances of conflict.

In their 2002 article, “The Arms Trade and the Incidence of Political Violence in Sub‐​Saharan Africa, 1967–97,” Cassady Craft and Joseph Smaldone identify another mechanism by which arms sales can fuel conflict. They find that autocratic governments importing weapons are more likely to use those weapons to oppress/​mistreat/​kill their own citizens since they now have a greater coercive capability.

But despite the straightforward logic behind the arms sales/​conflict connection, most work on the topic to date has relied on case studies, which are wonderful for highlighting potential causal mechanisms but not much use for establishing whether those mechanisms hold across the time and space. Until recently there had not been any work using statistical methods that would allow scholars to state with confidence which direction the causal mechanism actually flows – that is, do arms sales precede conflict or do impending conflicts lead to increased arms sales? Happily, the most recent article on arms sales by Oliver Pamp and his colleagues in the January 2018 issue of the Journal of Peace Research entitled, “The Build‐​Up of Coercive Capacities: Arms Imports and the Outbreak of Violent Intrastate Conflict,” uses a simultaneous equations model to overcome this problem. Looking at the relationship between arms sales and the outbreak of civil conflicts, the authors confirm the general thrust of previous research, concluding that:

“…while arms imports are not a genuine cause of intrastate conflicts, they significantly increase the probability of an onset in countries where conditions are notoriously conducive to conflict. In such situations, arms are not an effective deterrent but rather spark conflict escalation.”

This new confidence in the arms sales/​conflict connection should compel serious revision to American arms sales policies. Since 2002 the United States has sold over $286 billion dollars of weapons to 167 countries. These exports have gone to numerous countries where the conditions were or remain ripe for conflict. U.S. arms transfers to an unstable Iraq preceded the emergence of the Islamic State, but wound up helping amplify the Islamic State’s military capability when it took vast quantities of American weapons from defeated Iraqi army units. U.S. arms sales over the past decade also helped prepare Saudi Arabia to launch its disastrous intervention in Yemen and enabled the Nigerian government to unleash more effective violence on its own citizens, just to list a few examples.

Academic research often gets a bad rap in policy making circles. In the case of arms sales and arms transfers, however, the scholarly literature has correctly pointed out the serious risks involved. If the United States is serious about preventing conflict and managing regional stability in trouble spots around the globe, it would do well to stop pouring gas on the fire.

This blog post was written with help from Jordan Cohen, a Ph.D. student in political science at the Schar School of Policy and Government at George Mason University.