By Tom Nichols
Nuclear war, the exchange of nuclear weapons between two or more states in open conflict. It’s unthinkable. It can’t happen.
Of course, nuclear war is extremely unlikely. Although the Bulletin of the Atomic Scientists  has placed the hands of its famous clock at five minutes to midnight, that doesn’t mean very much and never has . The fact of the matter is that world nuclear inventories, led by reductions in the United States and Russia, have never been lower, and none of the major powers expects a nuclear conflict in the way they did during the Cold War. To crib a line from Captain Jack Sparrow, however, nuclear war is not impossible, it’s improbable, and a nuclear war could take place in more ways than you might think, sparked by any number of occurrences from a pure accident to an intentional strike.
I’m going to focus here on a war that could involve the United States and its allies on one side, and Russia or China on the other. Nuclear conflict between India and Pakistan, or between a future nuclear-armed Iran and Israel, is unlikely but far easier to imagine than a global nuclear conflict. Indeed, this is one reason Americans don’t think about nuclear war very much anymore: they think it will happen somewhere else. (If a regional limited war takes place, however, you’ll know it: even a small exchange of nuclear weapons will create a global environmental catastrophe  that will dwarf Chernobyl or Fukushima.)
(This first appeared in 2014.)
A small regional war, awful as it would be, would not destroy the United States nor threaten the end of the human race. A nuclear conflict of any serious size in the Northern Hemisphere, however, would effectively mean the end of the modern era. Further human progress would be subordinated to the basic needs of survival for years, if not decades, to come. A war between India and Pakistan would kill millions and pollute the earth for an eternity. But it would not threaten to bring the entire global system to a halt, or potentially lead to the release of thousands of warheads against of hundreds of cities across the globe, the “unthinkable” war for which Americans spent decades preparing, and for which we still maintain an arsenal of strategic weapons deliverable by air, land, and sea.
So how do we begin each of the nightmare scenarios?
1. Mechanical Accident:
The classic war-by-accident novel is Fail-Safe, in which a computer blows a fuse and the Air Force melts Moscow. Most people don’t read Fail-Safe anymore (which is why I make my students read it now), but almost everyone has seen WarGames and The Terminator, both of which are part of an entire genre of science fiction in which military computers decide not to take orders from pesky humans about who gets to fire nuclear missiles. That’s what makes them fiction, of course. Nuclear weapons are not sentient beings; Skynet is not self-aware and never will be. They’re just machines, and machines can fail on their own, with little human involvement.
As terrifying as it is to think of a war generated by a random mechanical hiccup, it’s important to note that this is the least likely trigger for a nuclear war. If anything, during the Cold War the superpowers spent so much time assuring the security of their arsenals against accidental use that both the Americans and the Soviets started to wonder whether they had too many  barriers in place that could prevent the intentional launch of the weapons in wartime . While the danger of an accidental launch of a strategic nuclear weapon is not zero, it is tiny.
That is, unless someone builds a “Doomsday Machine” that takes the human beings out of the loop. And who’d be crazy enough to do that?
Turns out the Soviet high command, in its pathetic and paranoid last years, was just that crazy. The USSR built a system called Perimetr, known informally in Russia as “the Dead Hand.”  Perimetr was essentially a computer system that would watch for signs of nuclear attack and retaliate on its own if the Soviet leadership was struck first and wiped out. (I explained this is more detail for National Geographic, which you can watch here .) We’ve since asked the Russians if it’s still on, and they’ve reassured us, with complete confidence, that we should mind our own business. Let’s hope they’re just being rude.
2. Human Error:
As long as there are machines run by human beings, there are going to be accidents. War, however, will not begin because a bomber crashes or a silo catches fire; rather, the error will lay in the misinterpretation of an accident by fallible human beings.
History is replete with such incidents. In 1995, the Russians forgot that the Norwegians had notified them of a rocket launch to put a weather satellite into space . The Russian high command told President Boris Yeltsin that they had a confirmed rocket launch from NATO over Russia. Fortunately, no one in the Kremlin assumed that Bill Clinton was trying to start World War III with a single warhead from Norway. Moreover, the warm relationship between Clinton and Yeltsin made the Russian president skeptical that Russia was under what Cold War strategists used to call a “BOOB,” or “Bolt Out Of the Blue” attack.
Similar mistakes have been provoked by flocks of birds, random computer glitches, and the sun glinting off cloud formations (which was interpreted by Soviet computers  as the fiery tails of multiple U.S. missile boosters). In each case, it was up to a human being to make the call: is someone really attacking us? Smart people in both Russia and the United States have prevented these mechanical errors from turning into Armageddon.
Nevertheless, the declassified files on these incidents won’t exactly help you sleep more soundly. In 1979, for example, NORAD, the joint U.S.- Canadian North American Air Defense Command, rousted White House advisor Zbigniew Brzezinski out of bed  and told him that a massive Soviet nuclear strike was incoming. Or so they thought, anyway: they were giving him a heads-up while they checked it out. Brzezinski was minutes away from waking President Jimmy Carter and handing him the codes to Hell when NORAD called back and said: Oops, nevermind. The computers goofed. Our bad. We’ll fix it.
And then it happened again in 1980.
The Soviets, who got wind of all this activity, politely sent a note to Carter asking him, in effect: What the is going on over there? It was a good question, and we’d have asked the same thing.
The key here, however, is not the technology, which makes a Fail-Safe type accidental launch nearly (but not entirely) impossible. Rather, the danger lies with human beings, who could issue orders to retaliate in moments of duress that cannot be undone. While this is less of a risk when tensions are lower, it’s always a possibility. Combining mechanical error with the natural flaws of human judgment multiplies the risk of accidental war from an infinitesimal risk to a very real possibility.
3. A Show of Force:
As we move from mechanical errors to human agency, things actually get scarier. Machines can make mistakes, but absent an international crisis and additional confirming evidence, no one goes to war on the say-so of a malfunctioning HAL 9000 . While journalists and nuclear safety experts have written some excellent books  about accidental detonations and other risks, I worry far more about a conscious decision to use nuclear weapons.
The worst mistake to make about nuclear weapons is to believe that they are ordinary arms, available for military use like any other. (This is sometimes called the “conventionalizing” of nuclear weapons.) The second worst mistake, however, is to believe that nuclear weapons are magic, and that using them solves problems that are otherwise politically or strategically intractable. This second error is what leads people into thinking about things like “demonstration shots” or nuclear shows of force, in which a nuclear weapon is exploded near, but not in, a conflict.
Ostensibly, such a dramatic demonstration will bring all of the combatants to their senses and call off whatever started the whole ruckus in the first place. (Nuclear game-players, by the way, almost never tell us why we’re at the brink. Politics is a messy business that just complicates clean, beautiful models and equations.) This idea is both seductive and dangerous: if our enemy sees our resolve, the logic goes, he will cease his predations. It is possible, of course, that a nuclear explosion could very well focus the attention of Russian, Chinese, or American leaders and invoke a “moment of clarity,” where everyone thinks very hard about what’s at stake and how much they’re willing to risk over it.
But to count on such clarity is a huge and potentially disastrous gamble. What happens if a demonstration of resolve merely provokes a corresponding act from the other side? One flexing of nuclear muscle (at sea, perhaps, or far from population centers on land) then leads to another. No one backs down, and so the next shot is a little closer to something that matters. Or perhaps a human being – again, always the weakest link in the nuclear chain – interprets a “demonstration” as the prelude to full-blown attack, and decides that safe is better than sorry. When it comes to strategic nuclear exchanges, there is no prize for second-place. The temptation to act, barely restrained during a crisis, might become overwhelming.
The fallacy at the center of this concept is the classic strategic error of assuming the predictability and controllability of inherently unpredictable and uncontrollable events. A nuclear show of force rests entirely on the hope that enemy leaders will clearly see a demonstration shot for what it is and not overreact. But misperception is a key part of international relations, and it is pure folly to assume that a nuclear explosion will have a clarifying, rather than a panicking, effect on the enemy.
4. We’re Dragged into it by Someone Else:
Sometimes, your worst enemies are your friends.
South Africa once had a nuclear arsenal . That’s not a widely known fact; the United States had its suspicions for years and tried in both Democratic and Republican administrations to put a stop to it, but to no avail. It’s probably not a reality anyone wants to think about too closely today, especially after the white apartheid government gave them up before handing power to the black majority at the end of the 1980s. It’s never been clear what the South African whites thought they were going to do with them, but one theory is that the weapons were meant to be an insurance policy against being overrun by some putative alliance of Soviet-armed Africans in nearby states.
The goal, however, wasn’t to kill the invading armies. Instead, it was to reveal the arsenal during the conflict – maybe even engaging in one of those “demonstration shots” – and thus spark a superpower crisis that would drag the United States into the mess and (I guess) save Pretoria at the last minute.
Even if the United States has no plans to involve itself in a nuclear conflict, U.S. allies or other powers might have ideas of their own. South Korea, for example, a few years back floated the idea that the United States might want to consider returning tactical nuclear arms to the Korean peninsula , a notion from which the Americans quickly distanced themselves. (We removed them all from South Korea in 1991, and they’re not going back.) If Iran gets a bomb Turkey or Saudi Arabia might follow suit. In each case, the presence of a nuclear weapon might be part of a smaller nation’s national defenses, but it is more likely to be bait for the U.S. to intervene before things go nuclear.
The step along this path to war involves the intervention of another power like Russia or China. In 1973, the Soviet Union threatened to intervene militarily in the Yom Kippur War a gamble that provoked an American move to a heightened state of nuclear readiness. What happens if fighting in the Middle East or Asia involves Russia or China, and smaller decides that a South African strategy of nuclearizing the conflict is the only hope of bringing the Americans into the fray?
Small states don’t have to develop their own arsenal for things to go awry. The path to nuclear war can always involve the traditional problem of alliances, and the constant danger, whenever nuclear armed powers are in proximity to each other, that one side or the other will see nuclear weapons as their trump card in a confrontation.
5. The “Sore Loser Scenario”:
Finally, there are paths to nuclear war that rely on the most durable source of war there is: human stupidity. If the major powers don’t bumble into a nuclear war, or get dragged into one by their friends, they can always just choose to launch one themselves.
During the Cold War, NATO’s strategy was actually quite simple. We can’t defeat you, we told the Soviets, and so if you invade Western Europe, you will be placing us in a position where we will have no choice but to repel you with battlefield nuclear weapons. You Soviets, having been nuked, will have no choice but to respond, at which point the U.S., Britain (and maybe even France) will turn the USSR into glass, even as you will do the same to us. So let’s not take that fateful step, because the first rifle fired in Wurzburg will inexorably lead to the last missile that falls on Vladivostok.
This chain of deterrent logic no longer applies to possible conflicts with Russia or China, in part because there is no longer a large battlefield between the U.S. and its nuclear opponents. If war breaks out over some smaller issue, there will be no way to pull back or even stabilize a military standoff, and a military loss by China or Russia is highly likely against a far superior (yes, even today) American force.
If China, for example, decides to press a claim in the Pacific and precipitates an open conflict with the United States at sea, it will almost certainly lose. At that point, China will have to make a choice: surrender whatever was at stake, or remove the U.S. fleet from the conflict by nuclear force. Likewise, if Russia and NATO come to blows in Europe – a scenario I thought ridiculous in the 1990s and now must reconsider – Russia will also lose, and like China will have no set of buffer states around it to prevent the fight from spilling back into Russian territory.
I call this the “sore loser scenario,” since the use of nuclear arms will serve only to make the victor pay a price equal to one the loser feels has already been suffered. Theoretically, the loser lashing out against the winner might create a kind of nuclear reset, but only the most optimistic Chinese strategist could hope that an act of the magnitude of a nuclear attack on a U.S. carrier could produce a military draw. (Put another way, it’s not a demonstration or a show of force if it involves instantly incinerating 5,000 U.S. military personnel.) The United States will be forced to respond, and then we’re off to the races.
Whether the Chinese really believe they could get away with this is unclear. But the Russians do, at least to judge by their own writings. In fact, the “sore loser” concept is embedded in Russian military doctrine. Russia is acutely aware of its conventional weakness; even as they torment Ukraine right under NATO’s nose, the Russians know that they have no chance against NATO without nuclear weapons, a role reversal between NATO and Russia whose irony has not gone unnoticed in the Kremlin. And so Moscow’s strategy, as analyst Nikolai Sokov and others have pointed out,  is to use nuclear weapons in a “de-escalatory” capacity: that is, when they’re losing a war, they’ll engage in a limited nuclear attack to get the enemy to back down.
Sadly, this isn’t the product of some half-baked recent order from current Russian President Vladimir Putin. Back in 1999, when Yeltsin was still in charge and Putin had only just arrived on the Moscow political scene, the Russian military held a major war game, Zapad-99 (or “West-99,” in case anyone missed the point). In this scenario NATO, for some utterly inexplicable reason, seized the Russian city of Kaliningrad, an enclave on the Baltic coast. This idea is so crazy that I am loathe to believe that any Russian planner really believed in it, but in any case, NATO had its nefarious way with poor Kaliningrad, despite heroic Russian measures.  And so the game’s final act was a set of four nuclear strikes on NATO,  two on Western Europe and two in North America. This ended the war and forced NATO to give back the Russian enclave.
As in the Chinese scenario, it is difficult to imagine that any Russian planner worth his salt really thinks that even the most feckless U.S. president would back down after Russian nuclear strikes kill and injure millions in Europe and America. More likely, as even Russian commentators have suggested , this might be bravado for internal political consumption. It could also be what nuclear mavens call “declaratory policy,” or the things nuclear powers say they would do in hopes of having never to do them, and which may not be very close to what they really train and prepare actually to do in a nuclear war. That would be my guess, but Zapad-99 and subsequent Russia thinking on nuclear war is, by any standard, disturbing stuff.
Unfortunately, American exercises aren’t much better. In 2006, for example, the United States conducted a drill called “Vigilant Shield”  in which we were at war with an assorted group of generic bad guys, including “Ruebek,” “Nemazee” and “Churya.” (If you can’t recognize Russia, North Korea, and China, you’re not using your imagination. I suppose it was easier than calling them “Ussia-Ray” and “Orth-Nay Orea-Kay.”) In the end, America settled everyone’s hash by launching a few strategic nuclear weapons at “Ruebek,” which brought the whole mess over whatever it was to an end.
One or two nuclear bombs, apparently, are aren’t all that destructive. In fact, “Vigilant Shield” included a hypothetical enemy nuclear strike against the Pentagon (which sits within sight of the Mall and just a short distance from the White House) that only killed 6,000 people. This remarkably low figure prompted journalist and Defense Department critic William Arkin to note that two of the core assumptions in the game were obviously that “nuclear warfare can break out for no particular reason at any particular time,” and that “small nuclear weapons, while bad, don’t really kill that many people.”
Military establishments are supposed to be full of worst-case pessimists. Nuclear warfighting ideas, however, rely on incredibly optimistic assumptions about universal rationality, near-perfect information, accurate perception, the absence of panic, and an orderly ability to control escalation in the midst of chaos. Someone making those assumptions are not the people you want in the Oval Office when “Ruebek” and “Churya” are off their leashes.
Before I conclude, let me reassure you that you’re in far more danger texting – or maybe reading something like this on your phone – while driving. The odds of a nuclear war are tiny, but they exist, and if we ever draw that black lottery ticket, the consequences will defeat our imagination. That doesn’t mean we don’t need to think about them, just as we think about how to forestall other kinds of unlikely disasters, including the man-made disasters of war. Much has been accomplished, but much more can be done, especially if there is even the smallest shred of bipartisan cooperation left on a matter like this one, where the fate of the country, and of the world, is continually at stake. That kind of cooperation is unlikely in the coming few years, nor are any further treaties likely to appear on the frozen ground between Russia and America. But the weapons will wait. And they will still be here when the next President takes office and swears, as he or she will almost certainly do, to get rid of them yet again.
Tom Nichols  is Professor of National Security Affairs at the Naval War College and an adjunct at the Harvard Extension School.