Editor’s Note: This is a guest post by Alexandre Debs and Nuno P. Monteiro, both of Yale University. In it, they discuss the causes of the Iraq War, a subject of some recent discussion at The Duck of Minerva. This post discusses their forthcoming International Organization article, which is now available as an “online first” piece and will be free to download for the next two weeks. Tomorrow we will run a response by David Lake [now available here].

In a forthcoming article in International Organization,Known Unknowns: Power Shifts, Uncertainty, and War,” we introduce a new theory connecting power shifts to war. Out theory provides novel answers to these questions on Iraq. Contrary to widely shared views according to which the war was caused by misperceptions and other irrational behaviors on the part of Saddam Hussein and the Bush Administration, we argue that the 2003 U.S.-led invasion of Iraq can be accounted for strictly within a rationalist framework.

Below we make four specific points on the causes of the Iraq War and then contrast our view with David Lake’s International Security article “Two Cheers for Bargaining Theory: Assessing Rationalist Explanations of the Iraq War” (PDF), where he argues that the Iraq War should prompt a behavioral revolution in the study of the causes of war. We conclude with brief implications for theory and policy.

Our Argument

Our first point is that the United States’ main motivation for invading Iraq on March 20, 2003, was to prevent suspected Iraqi nuclearization, which Washington thought would bring about a large and rapid shift in the balance of power in favor of Iraq. During the run-up to the invasion, the U.S. government’s casus belli rested on suspicion that Saddam was developing WMD — including nuclear weapons — thus presenting an imminent threat. Iraq’s nuclear acquisition would represent a large and rapid power shift that would make Saddam immune to any externally-driven regime-change efforts, ending his vulnerability to U.S. military action. The cost of war against a non-nuclear Iraq, in contrast, was expected to be relatively low, as U.S. forces would, given the precedent of the 1991 Gulf War, no doubt prevail. Specifically, the cost of a preventive counter-proliferation war against Iraq was expected to be orders of magnitude smaller than the expected cost of deterring, not to mention deposing a nuclear-armed Saddam. This difference accounts for U.S. insistence in guaranteeing Iraqi non-nuclear status, if necessary by force.

Second, the terrorist attacks of September 11, 2001, led U.S. decisionmakers to attribute more worrisome consequences to suspected Iraqi nuclearization, thereby accounting for the timing of the war. Iraq had been suspected of not abiding by the terms of the post-Gulf War cease fire, which precluded the country from developing WMD, but an invasion did not happen until the events of 9/11 undermined the U.S. administration’s trust in the intelligence community’s ability to detect security threats in a timely manner. In the aftermath of the attacks, the Bush Administration became particularly worried, based on flimsy intelligence, with the possibility of an Iraqi nuclear handoff to a terrorist group for use against the U.S. targets. The U.S. administration’s higher sensitivity to a low probability event (Iraq’s nuclear acquisition) made peace harder to sustain. In this sense, the invasion of Iraq represented the paradigmatic application of the ‘one percent doctrine,’ attributed to Vice President Dick Cheney. This doctrine suggests that, in the post-9/11 security environment, the United States must deal with ‘low-probability, high-impact’ events as if they were certain. Thus the United States acted as if Iraqi nuclearization were all but certain and launched a preventive war, which subsequently proved mistaken.

Third, the war was the result of the imperfect information U.S. leaders possessed about the Iraqi WMD program and their inability to eradicate uncertainty about the status of Iraq’s nuclear program. Enjoying a preponderance of power and determined to avoid the repetition of 9/11, the United States demanded incontrovertible evidence of Iraq WMD disarmament. Unable to obtain it, U.S. policymakers feared that Iraq would be tempted to build a nuclear weapon and place Washington before a fait accompli. Under mounting pressure, Saddam agreed in September 2002 to let U.N. inspectors in for the first time in nearly four years. Still, these inspections produced ambiguous results. At the same time, based on the intelligence available to most Western governments, “[a] responsible judgment could not have been that the [WMD] programs had ceased” (Jervis 2010, 155). This uncertainty underpinned a broad political consensus in Washington that Saddam intended to acquire a nuclear arsenal, justifying support for the war. Based on this rationale, the United States decided to launch a preventive war that ultimately proved to rest on mistaken grounds. Only after the war would it became clear that Iraq possessed no WMD and had no consistent WMD programs.

Finally, our theory helps account for why Washington launched an attack against Iraq rather than North Korea, a state that in fact possessed a nuclear-weapons program and would ultimately go nuclear. In our view, U.S. interactions with North Korea in the run-up to its nuclear acquisition display a key difference vis-à-vis Iraq: given Pyongyang’s ability to impose heavy costs on the United States and its allies using its conventional “sea of fire” strategy in case of a military conflagration, the cost of a preventive war against North Korea was expected to be much greater than that of a war against Iraq. By the same token, the effect of North Korean nuclearization would be relatively small, given the limited range of policy options available to the United States even vis-à-vis a non-nuclear North Korea. This meant that preventive war against North Korea was not rationalizable. 

Alternative Approaches

For some, it is impossible to provide a rationalist account of the Iraq war. In an important article, David Lake argues that the Iraq War highlights the need of a behavioral revolution in international-relations theory.

To begin with, Lake is quite generous towards the rationalist framework, giving it “two cheers” and conceding that it captures most of the strategic tensions of the case. Nevertheless, Lake argues that the rationalist framework suffers from two shortcomings that ultimately warrant a behavioral revolution. First, the two main causes of conflict in the rationalist framework –- information and commitment problems –- are constant features of the world system. Therefore, according to Lake, they cannot explain why the United States invaded Iraq and not other countries, such as North Korea. Second, for Lake, the war was caused by irrational factors: cognitive biases and self-delusion. Washington did not obtain the best information about the cost of the war and ignored evidence that Iraq had terminated its WMD program. Saddam Hussein, for his part, did not assess the level of U.S. resolve and sent mixed signals aimed at multiple audiences, including domestic and regional enemies as well as the United States.

In our opinion, Lake is actually too generous toward the rationalist framework.  According to him, “[b]argaining theory suggests that a fundamental cause of the war, and a key bargaining failure, was Iraq’s inability to commit credibly not to develop WMD or share the resulting technologies with others, including terrorists.” (Lake 2010/2011, 23) We agree that this is the fundamental friction that contributed to the war. However, this dynamic is not accounted for by the existing rationalist framework. The reason is that in the traditional framework, power shifts are exogenous, i.e., they “just happen.” In this sense, the rationalist framework cannot speak of a state’s attempt to acquire military means and of the danger this poses for peace.

In our work, we address this shortcoming and analyze a state’s decision to acquire nuclear weapons as a costly investment with delayed returns. We find that under perfect information, peace always prevails, no matter how large is a potential shift in the balance of power. Put simply, if a state expects a significant negative shift in the balance of power, and can perfectly detect the militarization attempt that would produce it, it may always issue a credible threat of preventive war, thereby deterring the other state from making the costly military investment in the first place. Realistically, however, information is imperfect and militarization attempts may not be detected. War may therefore occur because a state cannot commit to refrain from attempting to acquire military means covertly.

As Lake writes, information and commitment problems are prevalent in the international system. If Lake sees this feature as a shortcoming of the rationalist framework, we see it as a strength: it focuses on fundamental features of the international system. Contrary to what Lake claims, however, this does not mean that the rationalist framework has no predictive power. While the information and commitment problems are “constant” features of the international scene, their severity — which determines the likelihood of war — depends on the strategic environment. We thus find that war is more likely, everything else equal, as the quality of the information one state has about possible militarization attempts by others decreases, and as the shift in the balance of power resulting from such attempts increases relative to the cost of preventive war. As we argue above, we can then explain why the strategic relationship with Iraq after 9/11 was especially conducive to war.

Does the realization, ex post, that Iraq had dismantled its WMD programs mean that U.S. concerns were “unreasonable”? The rationalist framework cannot explain the origin of preferences. In this case, it cannot explain why the Bush Administration saw potential Iraqi nuclearization as causing such a momentous shift in the balance of power. It can, however, help us understand how a decisionmaker weigh the risk of different options as a function of the strategic environment. As we explain above, a rational decisionmaker would be more prone to prosecute a war against Iraq after 9/11 than against other likely targets.

Does the realization, ex post, that the U.S. administration was highly resolved (i.e., that it had a high-intensity preference for avoiding Iraqi nuclearization) mean that Saddam was irrational in entertaining his doubts? The rationalist framework argues that enemies have incentives to exaggerate their resolve. Furthermore, Saddam did possess a strategy to placate the United States. First he hoped that Russia or France would oppose a U.S. invasion and that, if such efforts were unsuccessful, he could produce enough casualties that U.S. public opinion would turn against the military campaign. Ultimately, these efforts were stymied by U.S. power preponderance. Still, Saddam’s strategy, if risky, was not irrational.

Lake may be right that multiple audiences played a role in explaining Saddam’s strategy. Indeed, Saddam refused to acknowledge the fact that his nuclear program had been dismantled, despite repeated U.S. requests to do so. This could be due to the fact that, as the Iraq Survey Group concluded, Saddam wanted to draw the benefit of strategic ambiguity when dealing with Iran, Israel, and domestic audiences.

Yet accommodating the role of multiple audiences does not mean that we should abandon the rationalist framework. There is indeed a large and growing rationalist literature on the effect of domestic audiences on international conflict (see, among others, Fearon 1994, Schultz 1998, Smith 1998, Ramsay 2004, Slantchev 2006, Debs and Goemans 2010, Debs and Weiss 2013). More importantly for our purposes, a focus on multiple audiences may not necessarily improve the explanatory power of our theories; it may in fact obscure it. After all, Saddam had been speaking to multiple audiences for more than a decade before the U.S. invasion.The fundamental dynamic leading to the war, therefore, did not stem from Saddam’s need to deal with multiple audiences. Rather, war was caused by Saddam’s inability to commit to refrain from investing in nuclear capabilities, coupled with U.S. concern that it might not detect an Iraqi nuclearization in time.


The controversy surrounding the United States’ decision to invade Iraq, which endures ten years later, continues to trigger some important questions for IR theory. While Lake encourages IR theorists to abandon the rationalist framework, we believe we should develop it further in order to take into account the specific challenges raised by Iraq. In our view, the important shortcoming of the existing rationalist framework highlighted by the Iraq war is that it treats power shifts as exogenous. Yet a key concern surrounding the invasion was the possibility that Iraq would produce a shift in the balance of power by acquiring nuclear weapons. Once we amend the rationalist framework to deal with endogenous power shifts resulting from states’ decision to militarize, we can capture many of the strategic considerations surrounding the war and can explain why the United States invaded in Iraq after 9/11. Our forthcoming article attempts to do so.

Arguing that the United States’ decision to invade Iraq can be understood in the rationalist framework does not amount to an endorsement of that decision. Scholars may, perhaps even should, enter the political debate on such momentous decisions, but their first duty is to develop theoretical frameworks capable of explaining historical patterns. The rationalist framework, rooted in a long tradition of analyzing the causes of war based on the features of the strategic environment, has so far proven capable of doing so. Alternative approaches may also generate unique and powerful predictions. For now, however, we believe that a behavioral revolution is unnecessary.

Finally, much in the historical debate about Iraq mirrors the current policy debate about U.S. options vis-à-vis the Iranian nuclear program. Some scholars have recently suggested that a war against Iran was the “least bad option,” (Kroenig 2012) arguing that the cost of a preventive war against Iran is small relative to the effect of Iran’s nuclearization. We disagree (Debs and Monteiro 2012). The cost of a preventive war against Iran would be high. Even a limited strike against Iran’s nuclear program would present significant costs, given that key facilities are located near population centers or buried deep underground. Furthermore, a limited preventive strike is highly unlikely to end the Iranian nuclear program, which would proceed, perhaps even intensify, in its aftermath. At the same time, given the limited options the United States possesses in dealing even with a non-nuclear Iran and the robustness of the U.S. and Israeli nuclear deterrents, the effect of Iranian nuclearization would be relatively low when compared with the costs of a strike. A preventive war against Iran is therefore not a desirable option.