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The Long Peace and Nuclear Deterrence

On October 27, 1962, Soviet submarine B-59 was trapped in the Caribbean, hunted by American destroyers dropping practice depth charges. The submarine's crew, out of contact with Moscow, didn't know whether war had started. The captain ordered nuclear torpedoes armed. To launch required agreement from three officers. Two agreed. The third—Vasili Arkhipov—refused.

If Arkhipov had said yes, a nuclear weapon would have detonated in the Caribbean. Mutual destruction would likely have followed. The Long Peace would have ended before it properly began.

We often attribute the post-1945 era of great-power peace to nuclear deterrence—the logic of mutually assured destruction that supposedly makes major war unthinkable. But stories like Arkhipov's suggest something troubling: the Long Peace might owe as much to luck as to deterrence.

What Is the Long Peace?

The term "Long Peace" was coined by historian John Lewis Gaddis to describe the absence of direct military conflict between great powers since World War II. This is historically anomalous.

Before 1945, great-power wars were regular occurrences. The Napoleonic Wars, the Crimean War, the Franco-Prussian War, World War I, World War II—major powers fought each other roughly once per generation for centuries. The 20th century alone saw two world wars that killed approximately 80-100 million people.

Since 1945: zero great-power wars. The United States and Soviet Union, despite intense rivalry, never fired shots at each other directly. China and the West have had tensions but no direct conflict. The European powers that fought each other constantly for five centuries now cooperate within the EU.

Eighty years of great-power peace is unprecedented in modern history. Something changed. The question is what.

The stakes couldn't be higher. If we understand why the Long Peace happened, we might preserve it. If we don't understand it—if we attribute peace to factors that weren't actually responsible—we might accidentally destroy the conditions that made peace possible.

The Nuclear Deterrence Hypothesis

The dominant explanation is nuclear deterrence. The logic:

Mutual Assured Destruction (MAD). Both superpowers had enough nuclear weapons to destroy the other even after absorbing a first strike. This made starting a war suicidal—whoever attacked first would be destroyed in retaliation. Rational actors don't start wars they cannot survive winning.

The crystal ball effect. Pre-nuclear leaders could hope that war might turn out well—that they might win quickly, that the other side might back down, that fortune might favor the bold. Nuclear weapons remove this uncertainty. Both sides know exactly what happens if war starts: mutual annihilation. No gamble, no uncertainty, just certain destruction.

Caution cascades. Even crises that might have escalated to war in previous eras get resolved short of direct conflict. The stakes are too high to risk. Cuban Missile Crisis, Berlin crises, various Cold War flashpoints—each time, leaders stepped back from the brink because the abyss was nuclear.

The deterrence hypothesis explains both the absence of great-power war and the presence of proxy wars. The superpowers couldn't fight directly, so they competed indirectly—through client states, covert operations, and regional conflicts where nuclear weapons weren't engaged.

The Problems with Deterrence Theory

Deterrence theory is elegant but potentially wrong—or at least incomplete:

The Rationality Problem

Deterrence assumes rational actors who can calculate costs and benefits, communicate credibly, and control their own military forces. But:

Leaders aren't always rational. Hitler invaded the Soviet Union. Saddam Hussein invaded Kuwait. Throughout history, leaders have made catastrophic miscalculations about war. Nuclear weapons don't prevent bad judgment—they just raise the stakes of bad judgment.

Organizations fail. The Arkhipov story illustrates that even when leaders want to avoid war, accidents and organizational breakdowns can bring it anyway. Broken communication, false alarms, unauthorized actions—these could trigger nuclear war regardless of what presidents and premiers intend.

Crises distort thinking. Under extreme stress, with information fragmentary and time pressure intense, leaders might not process decisions the way deterrence theory assumes. The Cuban Missile Crisis saw sleep-deprived leaders making snap decisions that could have ended civilization. We got lucky.

Deterrence can fail even when both sides want it to succeed. A leader might rationally not want war but take an action that the other side interprets as preparation for war, triggering preemptive action. Spiral dynamics, security dilemmas, and commitment problems can produce war even between rational actors who would prefer peace.

The Near-Misses

The Cold War featured numerous incidents that could have triggered nuclear war:

Able Archer 83. A NATO military exercise was so realistic that Soviet leaders feared it was cover for a genuine first strike. They put their nuclear forces on alert. If anyone had panicked, war could have started.

The 1983 Soviet early warning false alarm. Lieutenant Colonel Stanislav Petrov watched as Soviet satellites reported incoming American missiles. Protocol required him to report an attack. Instead, he judged it a false alarm and didn't report. He was right. Had he followed protocol, Soviet leaders might have launched.

Multiple technical glitches. Both American and Soviet systems generated false alarms—computer errors, misinterpreted data, equipment malfunctions. Each time, human judgment prevented escalation. But human judgment is fallible.

These near-misses suggest that deterrence has worked so far—but "so far" is the operative phrase. A system with multiple close calls over 80 years might not survive another 80 years. We might be living on borrowed time.

The problem is statistical. If there's even a 1% annual probability of accidental nuclear war, over a century that compounds to a 63% probability of catastrophe. The near-misses suggest the real probability might be higher. We've been rolling dice with civilization, and so far we've been lucky. But probability eventually catches up.

The Problem of Extended Deterrence

Nuclear deterrence works (if it works) for existential threats. Would the United States really start a nuclear war to defend West Germany? Taiwan? South Korea?

"Extended deterrence"—threatening nuclear war over attacks on allies—is less credible because it's not self-defense. Soviet leaders might have doubted whether America would truly sacrifice New York to save Berlin. This ambiguity creates instability: aggression against allies might seem feasible if the nuclear threat isn't believed.

Alternative Explanations for the Long Peace

Maybe nuclear deterrence matters less than we think. Other factors might explain great-power peace:

American Hegemony

The post-WWII era saw unprecedented concentration of power in the United States. American military dominance, economic centrality, and alliance network might have suppressed great-power conflict through preponderance rather than balance.

In this view, the Long Peace is the American Peace—maintained not by nuclear weapons but by overwhelming conventional advantage that makes challenging the United States seem futile.

Economic Interdependence

Global trade and financial integration have made war enormously costly. Major economies are so intertwined that conflict would devastate all parties economically.

The logic: if China and the United States went to war, both economies would crater. Supply chains would collapse. Financial markets would implode. Neither side could "win" in any meaningful sense. This economic deterrence might operate independently of nuclear weapons.

International Institutions

The post-war order created institutions—UN, IMF, World Bank, WTO, NATO, EU—that provide forums for dispute resolution, create expectations of peaceful behavior, and raise costs for aggression.

Perhaps these institutions, not nuclear weapons, explain the peace. They channel competition into peaceful arenas, provide off-ramps from crises, and create shared frameworks that make cooperation easier.

Changed Norms

Maybe war has simply become morally unacceptable among developed nations. Conquest is illegitimate. Territorial expansion is taboo. War of aggression is criminalized. These normative shifts might explain peace even if nuclear weapons had never been invented.

The Key Question: Are We Safe?

The debate matters because it determines what we should do:

If nuclear deterrence explains the peace, we should maintain it—despite proliferation risks, despite accidents, despite the moral horror of threatening mass murder. The alternative is great-power war.

If other factors explain the peace, nuclear weapons might be net negatives—adding catastrophic risk without providing much benefit. We should work toward abolition, accepting some conventional war risk to eliminate nuclear annihilation risk.

If luck explains the peace, we're in serious trouble. Eighty years of good fortune doesn't mean we'll have another eighty. The near-misses suggest the system is unstable. Eventually, our luck runs out.

Most likely, it's some combination. Nuclear deterrence probably contributes to peace, but so do other factors, and luck has played a larger role than we'd like to admit. The Long Peace is real but fragile—maintained by multiple factors that could erode.

The Future of the Long Peace

Several developments challenge the conditions that maintained post-WWII peace:

Multipolarity. The bipolar Cold War era was dangerous but stable. The emerging multipolar world—with the US, China, and potentially others as major powers—has more potential flashpoints and more complex deterrence calculations.

New technologies. Cyber weapons, hypersonic missiles, AI-enabled systems—these create new instabilities that Cold War frameworks didn't anticipate. Can deterrence work when attacks can be launched with ambiguous attribution? When AI might make decisions faster than humans can process?

Declining institutions. International institutions are under strain. The UN is often paralyzed. Arms control agreements have collapsed. Norms against aggression eroded when Russia invaded Ukraine. The institutional infrastructure of peace is weakening.

Great-power rivalry intensifying. US-China tensions are growing. The economic interdependence that might have provided deterrence is being deliberately decoupled. The conditions that maintained peace are degrading.

Climate and resource stress. Climate change, water scarcity, and resource competition could create new drivers of conflict that existing frameworks weren't designed to handle. Great powers might clash over migration flows, access to resources, or regional instabilities triggered by environmental stress.

The Takeaway

The Long Peace—80 years without great-power war—is one of the most important facts about the modern world. Whether it resulted from nuclear deterrence, American hegemony, economic interdependence, institutions, norms, or luck shapes how we understand the future.

Nuclear deterrence probably plays some role. The impossibility of winning a nuclear war creates powerful incentives for caution. But near-misses suggest the system is dangerous, and other factors likely contributed significantly.

The most sobering possibility is that luck played a larger role than we acknowledge. Multiple times, individual judgment calls prevented nuclear war. If Arkhipov had agreed, if Petrov had followed protocol, if various false alarms had been handled differently—we might not be here to debate the causes of peace.

This should make us humble about the Long Peace's durability. It's not a law of nature. It's a contingent achievement, maintained by factors that can change and luck that can run out. Preserving it requires understanding what created it—and that understanding remains incomplete.

The Long Peace and Nuclear Deterrence

What Is the Long Peace?

The Nuclear Deterrence Hypothesis