On 6 August 1945, the first atomic bomb to be used in anger detonated over the city of Hiroshima, Japan. Three days later, it was Nagasaki’s turn. That was the last such attack. Despite the worst of the cold war’s close calls, like the Cuban missile crisis, no other nuclear weapons have ever been used outside of testing. Seven decades later, it is worth asking: could it happen again? Here are five possible nuclear use scenarios.
Major power nuclear war
During the cold war, the most likely scenario seemed to be a conflict between the US and the Soviet Union, each of which possessed many thousands of nuclear weapons. Three other countries eventually entered into the “nuclear club” as well, developing relatively large, sophisticated arsenals with global reach. Today, the idea that the US, Russia, UK, France or China would start a nuclear war seems considerably more remote than it once was.
But it is not entirely off the table. The US and Russia still possess thousands of weapons each, with the other three nations possessing arsenals in the hundreds. Tensions over regional affairs, such as the fighting in Ukraine, always carry the threat of spilling over into larger conflicts. War strategists call this possibility “escalation”, where one side, perhaps without realising it, pushes the other side into a slightly larger response, which leads to another response, and so on until – at its very worse – a full nuclear exchange, the sort of thing that can kill millions.
None of these powers want this sort of thing to happen – it’s not in their interest to be mutually annihilated, and their arsenals are sophisticated enough that nobody thinks they could get away with a sneak attack without fearing reprisal. Despite sometimes having blistering rhetoric, they take pains to avoid it. Could it still happen? It’s not impossible. But it’s probably not as likely to happen today as it might have in the 1960s or 1980s, when tensions were at their highest.
Minor power nuclear war
What about the other nuclear powers, whose arsenals are smaller and who do not yet quite have global reach? Into this category we might put India, Pakistan, Israel and North Korea.
Could two of these nations wage war against one another? The scenario that has kept experts up at night for a long time has been that of a “nuclear exchange” between India and Pakistan, whose proximity, comparable nuclear arsenals, and long history of disagreements make their situation seem especially dangerous. Notably, they also have different nuclear doctrines: India, with its large conventional army, has indicated it would not use nuclear weapons first, but Pakistan has indicated that in the event of an overwhelming conventional attack, it may feel sufficiently threatened to go nuclear. These sorts of “asymmetries” make nuclear wonks anxious, because it means that each side has a different “red line”, and the other side may not know exactly where that line is drawn.
For many experts, something involving smaller nuclear powers might be the most likely scenario on this list for a significant nuclear exchange. Lest anyone who doesn’t live in these regions think that this is not something to worry about, scientists have run models that have concluded that even a relatively “minor” exchange of only a few hundred weapons, aside from killing millions in the region in question, might alter the global climate in such a way as to drastically reduce crop production.
Nuclear weapons state v non-nuclear state
Could a nuclear weapons state, minor or major, use such a weapon against a non-nuclear power? It’s obviously not impossible: the only time that nuclear weapons were ever used in war so far was one nuclear power with very few weapons (the US) against a non-nuclear power (Japan). In terms of major nuclear weapon powers, it seems unlikely that the states today with large conventional militaries would think nuclear weapons were worth using.
But what about states that are more vulnerable, with smaller militaries? One might worry, say, about a war between Israel and its neighbours, or North Korea against South Korea. The tricky thing here is that with these states, the non-nuclear powers might not know where that line might be drawn for the states with the bomb. Again, these kinds of “asymmetries” might make the chance for misunderstanding high.
Since the late 1960s, people have worried about the possibility that a group of terrorists (“non-state actors”) might acquire nuclear weapons. The ability to natively produce the nuclear fuel for a bomb (enriched uranium or separated plutonium) is still restricted only to entities the size of states, though the technical requirements have decreased over the years. But it is unlikely for the moment that any terrorist group, even one with significant resources, would be able to muster the technical and industrial expertise necessary to produce the fuel themselves.
Could a terrorist group steal the fuel? Potentially. For many years after the fall of the Soviet Union, there were concerns that Russian supplies of bomb-grade uranium and plutonium might be vulnerable to theft or diversion. There are no concrete indications that this has occurred, but the record-keeping for this period was so poor that it’s not clear that anybody would be able to tell if it had taken place. The situation today is considerably better, though the physical security around the plants that create and store these materials has often left a lot to be desired. As recently as 2012, for example, a group of peace activists (including an 82-year-old nun) managed to break into the American “Fort Knox” of enriched uranium.
Would a state give weapon-grade fuel, or a full weapon, to a terrorist organisation? This is usually judged as not particularly likely, as scary as it sounds. In the event of a terrorist nuclear detonation, scientists would likely be able to determine the origin of the nuclear fuel in the bomb, since every plant that makes nuclear fuel has slight differences in its product output, and these can be detected even in the wake of an explosion.
Could a terrorist organisation steal an in-tact weapon? Many nuclear weapons today are kitted out with sophisticated electronic locks that would prevent their being used, or tampered with, by anyone lacking the proper codes. In theory, these kinds of countermeasures would make it very hard to use a stolen nuclear weapon, even if the heist could be pulled off.
Accidental nuclear detonation
Could a nuclear weapon created by a nuclear state accidentally go off? In the 1950s and 1960s, the US had dozens of “near misses”, such as bombs that crashed with planes, or fell out of planes, or caught fire for extended periods of time.
Could such an occurrence result in a significant nuclear yield? With older generations of weapons, it was not as unlikely as we’d like to think (Eric Schlosser’s Command and Control is a disturbing read in this respect). Many of these bombs were not designed with long-term safety as their primary consideration. Later generations of warheads were built so that the chance of an accident producing a nuclear explosion would be exceedingly rare. But we know very little about the weapon designs of most states, and whether they prioritise safety better than the US used to in its older designs.
Taking these scenarios all together, how likely is it that the world will once again see a nuclear weapon used against a city? If we live in a world with nuclear weapons, there will always be a risk greater than zero of “it” happening again. This worrisome uncertainty is one of the truths of the nuclear age and there is no easy way around it. Even attempting to get rid of all nuclear weapons might not resolve such a fear entirely – after all, it is always possible that a state might keep a very small stockpile of nuclear fuel hidden, just in case.
The threat of nuclear war was, for many decades, the primary existential threat to humanity. Today, it has probably been dethroned by the threat of man-made climate change. But the uncertainties are still high enough that nobody should feel too comfortable about a world with more than 10,000 nuclear weapons, even if things are probably not as bad as they once were. Nuclear war is no longer at the very top of the list of things to worry about – but it’s still on the list.