Arms Diffusion and War

The authors present a model of the relationship between the spread of new military technologies and the occurrence of war. A new technology could shift the balance of power, causing anticipatory war as one side tries to prevent the other from obtaining it. When one side already has it, war is more likely when the shift in power is large, likely, and durable. When neither side has it, war is more likely when the expected shift is asymmetric (e.g., one side is more likely to get it) and when the two sides fear that a war will occur once one of them has it. The authors illustrate the model with historical examples from the spread of firearms (the Musket Wars in precolonial New Zealand) and of nuclear weapons (the end of US nuclear monopoly and the 1967 Six-Day War). A broader implication is that major power competition can unintentionally cause wars elsewhere.Governmen

Peaceful Uncertainty: When Power Shocks Do Not Create Commitment Problems

Does a shock to the balance of power cause the advantaged actor to exploit its newfound advantage by initiating conflict? The modeling literature on commitment problems as a source of war makes a central assumption that states know and anticipate power shifts. We relax this assumption such that states must estimate future power shifts by looking at past and present capabilities—both their own and those of their adversaries. We incorporate these estimates, and their attendant uncertainty, into a model of war. We find that commitment problems remain a source of war, but that the existing models overpredict war by ignoring this dynamic. States continuously updating their estimates and accounting for uncertainty promotes peace. It follows that the apparent window of opportunity—in which the power balance becomes suddenly favorable to one side—poses less of a threat to peace than previous theories suggest. This result has applications to nuclear proliferation dynamics and conflict in general. We find empirical support for the model in tests analyzing power shifts and interstate wars

Accounting for Extra-Dyadic Sources of International Outcomes

Leaders consider the broader international landscape when making foreign policy choices. This landscape could encompass a single external actor, the local region, or even the whole international system. Quantitative analyses of international outcomes, however, frequently do not account for this broader context. This study suggests a corrective, illustrating the value of incorporating extra-dyadic variables into analyses with dyadic and monadic outcomes. The challenge is to parsimoniously capture theoretically salient elements of the multilateral environment. We contend that a measure that links distributions of power within any k-set of relevant states to uncertainty over conflict outcomes is a promising option for two reasons. First, the measure builds from and accords with canonical theories of international politics. Second, it offers scholars a simple and flexible means to define and account for the set of states that constitute the relevant multilateral landscape. Illustrative applications linking power distributions and outcome uncertainty to alliance formation and pursuit of nuclear weapons demonstrate that extra-dyadic factors consistently influence foreign policy outcomes. This study thus shows that situating such outcomes within their broader context is both feasible and substantively important. Moreover, it contributes to recent efforts to address shortcomings of monadic and dyadic studies