Institutions check miscalculation.

The risk of war by miscalculation is a popular scholarly subject and a frequent concern of policymakers. Theories of war by miscalculation assume either ignorance by decisionmakers, bad faith by policy participants (usually the military), or a mechanistic series of exchanges that obviate the need for policymakers to display judgment and responsibility. Yet historians struggle to produce evidence that political leaders were either ignorant of the risks they were choosing or emasculated from any ability to affect the course of events. Theories of accidental war are, as Geoffrey Blainey has said, “a description masquerading as an explanation.”[1] Instead of explaining historical events, the myth of accidental war provides an intricate puzzle for intellectuals, a justification for moralists to fear military subversion of political decisionmakers, and an evasion of culpability for those decisionmakers.

The debate is not esoteric—it has urgent policy applications. U.S. policy regarding Russia’s February 2022 full-scale invasion of Ukraine has been heavily influenced by U.S. President Joe Biden and his administration’s concerns about “a third world war.”[2] Russia violated the sovereignty and the internationally recognized territory of Ukraine, despite its commitment to respect Ukraine’s security in the 1995 Budapest Memorandum. Failing to achieve its political objectives on the battlefield, Russian strategy shifted to targeting civilian dwellings, destroying infrastructure, and committing mass atrocities. All of these actions violate Russia’s international commitments and overtly challenge the Biden administration’s leadership of the rules-based international order, as well as its pledge to “stand against human rights abuses wherever they occur.”[3]

Although rational calculations of power ought to dictate Russian aversion to expanding the war from a trajectory of losing to Ukraine to one of more rapidly and decisively losing should the United States become a direct combatant, the Biden team’s policy is predicated on concerns that uncontrollable escalation could result from U.S. assistance to Ukraine. To avoid an accidental war with Russia, the Biden administration has defended the international order by timidly progressing from declining before and in the early stages of the invasion to provide weapons to Ukraine because they would quickly end up in Russian hands if Russia won as expected, to refusing to provide “offensive weapons,” to providing “offensive weapons” but not those that could reach Russian territory, to providing weapons that could reach Russian territory but making Ukraine promise not to use them at those ranges, to allowing Ukraine to target Russian forces in Crimea, to providing tanks and training in the United States.[4] Out of concern the United States could unavoidably be drawn into direct combat against Russia, the strongest power in the international order is conveying the limits of its interest to a violent transgressor losing a war against a lesser power.

The idea that war happens by accident is prejudicing U.S. policy toward self-deterrence.

The idea of accidental war also influences U.S. policy toward China, the “pacing challenge” in its great power rivalry, according to the Biden administration’s October 2022 National Security Strategy.[5] The United States publicizes Chinese infractions, like the construction of island military bases in the South China Sea, but does not enforce compliance. And China is playing that concern to its advantage, undertaking demonstrations of its willingness to violate U.S. sovereignty, initiating dangerous military incidents, explaining provocations as its military acting without political knowledge, and refusing to answer military hotline calls during crises. This shows that the errant notion that war happens unaccountably, that political leaders are powerless to prevent escalation, that militaries will act independently of political control and blunder states into conflict has immediate policy relevance. The idea that war happens by accident is prejudicing U.S. policy toward self-deterrence; national security experts should instead be more concerned about deliberate choices for war as they think about deterrence and escalation control.

What Is Meant by Accidental War?

It is very difficult to know with precision the combination of political commitment to objectives, military power, the ability to marshal economic resources, and the social fortitude that combatants possess until they fight. Blainey persuasively has argued that war is how relative power is determined in the international order.[6] As Carl von Clausewitz explained and Russia’s invasion of Ukraine demonstrates, war is a gambling game. If accidental war means nothing more than leaders misjudging their relative power, then every war is a mistake. This is because, as Blainey has concluded, “war is usually the outcome of a diplomatic crisis which cannot be solved because both sides have conflicting estimates of their bargaining power.”[7]

Strikingly, across nearly eighty years of the nuclear age . . . there have been few accidents, and none of them led to an automatic escalation or failure by political and military leaders to make judgments dampening the prospects of war.

To be intellectually useful, a robust definition of accidental war matters. At its most basic, accidental war could be mischance—a confused signal, the technical failure of a weapon, or the accidental launch of a missile. Alexander George has termed this kind of scenario “inadvertent war.”[8] It is striking that across nearly eighty years of the nuclear age, incorporating U.S. and Soviet arsenals in the tens of thousands and less developed countries designing indigenous arsenals and delivery systems, there have been few accidents, and none of them led to an automatic escalation or failure by political and military leaders to make judgments dampening the prospects of war.

But although scholars engaging in the debate use the terms accidental and inadvertent war interchangeably, genuine inadvertence is mostly not what is meant in the debate about accidental war; rather, mostly what is meant is willful subversion of political intent.[9] George distinguished inadvertent from accidental war, defining the latter as “one that starts because of unauthorized activities by individuals below the leadership level in the chain of command.”[10] Meanwhile, Marc Trachtenberg has defined accidental war as “one in which the political process— a process that would normally lead to a peaceful settlement of the dispute at hand—is overwhelmed by forces welling up from within the military sphere . . . If the political leaders thought the risks were relatively limited, but the military structure in place created a much greater level of risk in time of crisis, then one could conceivably have what, from the point of view of the political leadership, would be an ‘accidental war.’”[11] Scott Sagan also has narrowed the aperture of unauthorized activities to the military, defining wars as accidental only when “there would have to be some activity or incident inside the military machine, without which war would not have occurred.”[12]

The idea of accidental war has been of particular interest to political scientists rather than historians, which seems a significant detail—the experts on concepts are intrigued, the experts of the case studies find no corroborating examples. No less a source than the distinguished military historian Michael Howard has rejected the idea, writing, “if history shows any record of ‘accidental’ wars, I have yet to find them.”[13]

An exhaustive study by Evan Luard of wars dating from 1400 CE to 1985 did not turn up a single case of accidental inception.[14] Sagan, a political scientist and proponent of the accidental war idea, has admitted as much, acknowledging, “in the major works by historians on the causes of war, however, the whole idea of accidental war is either conspicuous by its absence or explicitly dismissed as conceptually confused and historically irrelevant.”[15]