Research
Published
Hulme, M Patrick, “War and Responsibility”, American Political Science Review (link)
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.
Hulme, M. Patrick, Erik Gartzke, Alex Braithwaite, and Lauren Gilbert. “Power, Parity, and Place: Why Forgetting the Loss-of-Strength Gradient Misses the Relative Power Relationship.” Journal of Conflict Resolution (link)
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.
Alliance Reassurance and the Image of the Imperial Presidency (with Matt Waxman)(Security Studies, 2026: link)
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.
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.
Revise & resubmit
“Nuclear Rivalry and Conventional War: Evidence from Elite Military Opinion” (w/ with Tyler Bowen, Michael Goldfien, Kendrick Kuo, and So Jin Lee) revise and resubmit at International Studies Quarterly
How do shifts in nuclear rivalry affect conventional conflict? Foundational accounts, such as the Theory of the Nuclear Revolution and the Stability-Instability Paradox, focus narrowly on the balance of nuclear capabilities. We argue that a broader set of factors, including nuclear posture, leadership traits, and diplomatic channels, can affect perceptions of escalation risk and preferences for the use of conventional force under the nuclear shadow. We test existing theories and our novel hypotheses with two conjoint experiments fielded among U.S. military elites. We find that shifts to the nuclear balance affect attitudes in a manner consistent with the Theory of the Nuclear Revolution and contrary to classic renderings of the Stability-Instability Paradox. However, we find that \textit{other factors}---less escalatory nuclear postures and cautious adversary leadership---contribute to stability-instability-like dynamics, simultaneously reducing perceived escalation risk and increasing support for conventional military action.
Under Review
The War Powers and the Search for Credibility: Untying Hands vs. Demonstrating Strength (Under review)
Why do presidents act unilaterally for smaller interventions but seek congressional authorization for major wars? Does seeking legislative approval increase or decrease threat credibility? This article presents a formal model of crisis bargaining that resolves these puzzles by distinguishing between two competing credibility mechanisms: "untying hands" and "demonstrating strength." Authorization lowers a leader's "loss responsibility costs" by sharing political exposure with lawmakers, thereby increasing the executive's willingness to use force and improving the state's bargaining position. Yet the act of seeking authorization can also reveal that the leader is sensitive to domestic political constraint. The model therefore implies that presidents face structural incentives to "feign imperialism": publicly proclaiming unilateral authority to preserve an image of strength while privately valuing congressional support for large-scale war. The argument significantly qualifies democratic constraint theory by showing that visible legislative constraints over war initiation can undermine one form of coercive credibility even as authorization strengthens another. Evidence from the Gulf and Vietnam Wars illustrates the mechanism and suggests that the Imperial Presidency may be partly a strategically cultivated facade.
The Essence of Congressional Influence: Power Without Participation in the Cuban Missile Crisis (Under review)
Scholars have long cited the Cuban Missile Crisis as the canonical case of unilateral presidential decision-making. EXCOMM excluded lawmakers, and Congress was not in session during the Thirteen Days of what Schlesinger called "the most dangerous moment in human history." Many have read the case as proof that in the nuclear age, only an imperial president can reign. Yet recent histories emphasize the role that congressional pressure played in policy formulation, both before and during the crisis. How could Congress have been excluded from the decision-making and yet so deeply influential in shaping it? This article resolves the paradox by distinguishing two types of legislative power in military crises generally: action-channel influence, exercised through genuine consultation or formal veto power, and incentive-rearranging influence, exercised by lawmakers restructuring the executive's strategic incentives. The crisis lacked the first but was a case of profound legislative power exercised through the second. The article not only provides extensive archival evidence that Kennedy actually acted pursuant to formal authorization from Congress — six decades of war powers scholarship notwithstanding — but also contributes to audience-cost theory by recovering the agency of the audience itself: legislatures do not merely assess costs, they strategically choose whether and how forcefully to assess them. The Thirteen Days unfolded in the shadow of Congress.
An Audience with Agency: Congressional Influence in International Crisis (with Andrew Kenealy) (Under review)
This article explains how Congress influences presidential decision-making during international crises. It argues that legislators can manipulate four costs to which presidents are exposed (inaction, belligerence, audience, and fighting) in ways that rearrange executive incentives, and in turn choice, at all crisis stages. It assesses expectations with new qualitative and experimental evidence. Investigations of the Cuban Missile and Syrian Chemical Weapons Crises drawing upon archival materials, novel messaging data, and original interviews show that presidents are sensitive to this capacity as the theory expects. A survey experiment provides causal evidence that congressional position-taking manipulates each cost as anticipated. Findings imply that congressional control over escalation, credibility, and constraint can be flexible and coercive; bridge IR models resting on public evaluations of executive behavior with American politics scholarship assigning Congress a central role in their formation; and reveal high democratic responsiveness in American statecraft that is nevertheless vulnerable to partisan polarization.
Legal but Lethal: The State of War in the Shadow of the Cold War (with Adam Saxton) (preparing for (re)submission)
The distinction between war and peace is central to international relations, yet states have rarely recognized any legal "state of war" since World War II. Existing explanations attribute this decline to legalization — either the outlawry of war culminating in the UN Charter (jus ad bellum) or the codification of international humanitarian law (jus in bello). Instead, we argue that the decline was driven by changing material conditions of war. Under traditional international law, a legal "state of war" denoted a conflict of unlimited means, scale, and geographic scope while also triggering alliance obligations. The advent of nuclear weapons in 1945 and the Cold War alliance blocs made major powers eager to avoid invoking such an unlimited legal category that could potentially trigger a nuclear World War III. In terms of normative development, we argue this made the state of war a "legally latent" category: not illegal or replaced, but avoided as extremely dangerous. Leveraging archival evidence of U.S. deliberations in the Korean War, Cuban Missile Crisis, and Vietnam War, we demonstrate that policymakers consistently chose legally suboptimal alternatives to a state of war to avoid escalation. We also demonstrate that some minor and middle powers, less constrained by nuclear risks, continued to assert legal states of war after 1945. Our findings contribute to theories of normative change, international law, and conflict escalation, while exonerating twentieth-century legalization movements for the collapse of the war–peace distinction and showing a novel use of international law as a tool of escalation management.