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Research

Hulme, M Patrick, and Erik Gartzke. 2021. “The Tyranny of Distance: Assessing and Explaining the Apparent Decline in U.S. Military Performance.” International Studies Quarterly 65(2): 542–50. (link)

There is a growing sense that U.S. military effectiveness has been on the wane in recent years.  Is this the case? If so, what are the reasons for the decay in American combat performance?  We first examine the available systematic evidence for American military decline, showing that the United States has indeed experienced a drop in the quality of outcomes of its military contests. Observers have offered a number of explanations for declining American military success, most predominantly  an increase in intrastate conflict after the Second World War. After showing that a decline in performance is observed even after fully excluding intrastate conflict, we propose an alternative explanation: the increasing distance-from-home at which the United States has been fighting. Distance is tyrannical: it saps military strength and increases the cost of contests, even as it reduces U.S. expertise and motivations to prevail. We then show that the distance from home at which the United States fights is the best predictor of the outcome of the conflict. We conclude by noting some avenues for future research and policy implications as the world returns to great power competition.

War and Responsibility 
(Forthcoming in the American Political Science Review)

Scholars and policymakers bemoan an imperial presidency in the war powers context, where the unilateral use of force is frequently interpreted as evidence of an unconstrained executive. Focusing on the strong blame avoidance incentives faced by politicians in the military intervention setting, I develop a model of the war powers focused on ``Loss Responsibility Costs". It suggests that presidents only risk full-scale war when they have the political cover provided by formal authorization, which forces lawmakers to share responsibility. Smaller interventions, in contrast, are frequently undertaken unilaterally because having the president act alone is consistent with congressional preferences for blame avoidance. Novel sentiment data based on tens of thousands of congressional speeches supports the claim that when the president acts unilaterally, they almost always act alongside lawmaker support, who favor intervention but avoid formally endorsing the endeavor. Altogether, it suggests legislators’ influence over war is much stronger than commonly appreciated.

Alliance Reassurance and the Image of the Imperial Presidency (with Matt Waxman)
(
Conditionally accepted at Security Studies)

Recent work in the alliance politics literature has highlighted various “strategies of reassurance,” including public reaffirmations of security guarantees, personal visits, economic sanctions, and force deployments. We argue that this extensive literature has overlooked a critical element in American reassurance of its allies: perceptions of an American presidency ready, willing, and able to act unilaterally (i.e., without authorization from Congress). Specifically, while allies seek for an American commitment to be “automatic” in case of attack, each U.S. defense pact contains a procedural clause conditioning the American commitment on its “constitutional processes.” This creates a “commitment gap” between the level of commitment required to effectively reassure allies and the level actually provided by lawmakers in the treaty text. In a self-help world, allies are highly sensitive to this disparity, pressuring the American executive branch to “bridge the gap” through means such as broad assertions of presidential power, demonstrative unilateral uses of force, and tripwire deployments, all of which constitutionally facilitate action absent congressional approval. The article illustrates the logic of the theory through case studies of American alliances with NATO, South Korea, the Philippines, and Thailand. It concludes by considering implications for the efficacy of tripwire deployments, contemporary efforts to reform the war powers, and broader debates over American grand strategy. The argument suggests that grand strategies that emphasize the importance of alliances effectively require an image of an imperial presidency.

Power, Parity and Proximity (with Erik Gartzke, Lauren Gilbert and Alex Baithwaite)
(Revise and Resubmit at
Journal of Conflict Resolution)

Research debating competing perspectives on power and war has yet to address the endogenous impact of proximity. If power declines in distance, then power relations between two nations differ at different points on the globe. Claims about the impact of parity or preponderance on conflict and peace then really only apply to particular points or regions in the space separating borders or national capitals. We use a formal bargaining model to demonstrate that dyads should be most prone to fight in places where each state’s capabilities, discounted by distance, are roughly at parity. We then assess this relationship empirically, introducing the directed dyad year location unit-of-analysis to capture the impact of geographic distance on power and the propensity to fight. Results confirm that disputes are most likely at locations where the distance-weighted capabilities of nations are roughly equal.

The War Powers and the Search for Credibility

American politicians have for decades perceived a close link between coercive credibility and the question of the war powers of Congress and the President, and yet scholars of political science have given relatively little attention to the subject. This article develops a formal model of the war powers, with a focus on the effect of asymmetric information over a Presidency's willingness to act unilaterally: the institution's sensitivity to "loss responsibility costs". A key intuition shown is that the primary effect of formal authorization from the legislature  is not purely informational, as prior models of domestic politics seemingly suggest. Instead, formal authorization serves as a functional role as an "incentives-rearranging" type mechanism, making intervention---and intervention at a higher scale---much more likely. Moreover, a vote in favor of war can make war less likely by removing the source of this information asymmetry. 

    At the same time, the model shows that the act of seeking authorization can expose the institution of the Presidency as a weak type; acting unilaterally serves as a costly signal of the Presidency's insensitivity to loss responsibility costs. Specifically, the scale of the potential use of force heavily determines which effect dominates. While Presidents benefit greatly from the political cover of formal authorization, they therefore resist appearing too eager for the backing of the legislature and will act unilaterally for smaller uses of force. Presidents are shown to have strong incentives to carefully cultivate and maintain an image of an "imperial presidency".

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