This essay was originally published in War: Perspectives from the Engelsberg Seminar, Axess, in collaboration with the Axel and Margaret Ax:son Johnson Foundation in 2015.

The question of why there has been a Long Peace, a period now of 70 years since the last major war between major powers, has generated as much debate as the question of the origins of the Great War of 1914. On the one hand, John Gaddis, who first used the term, is clear that it had something to do with nuclear weapons. On the other hand, Steven Pinker asserts that this welcome development has little or nothing to do with the prospect of mass destruction but is the result instead of the triumph of the good of our ‘better angels’ in a Manichean struggle with the evil of our ‘inner demons’. The ‘better angels’ connote empathy, self-control and morality and have encouraged a progressive civilising process. The ‘inner demons’ lead to instrumental violence, domination, revenge, sadism and ideology. These two approaches can be distinguished as one offering a theory of coercive peace, which assumes that tendencies towards conflict have been suppressed through fear of the consequences of escalation and, the other, a theory of normative peace, which assumes that the major powers have adopted a more civilised approach to conflict and have come to reject violent means to the resolution of disputes.

These two positions are not necessarily exclusive. Few who stress the importance of nuclear deterrence would deny the importance of many other factors, including the nature of the issues in dispute, as well as normative factors. But those who believe in the normative peace do tend to have a problem with the idea that nuclear deterrence might have played a role. They are wary of arguments for maintaining alert nuclear arsenals, instead of proceeding to complete disarmament, and nervous that this is a dangerous basis for peace — for once it ceases to work, the effects could be disastrous. Thus Steven Pinker, in The Better Angels of our Nature, seeking to defend his thesis of the decline of war, attempts to write them out of post-1945 history, as if they had no discernible effect on behaviour. ‘Thankfully’, he writes, responding to Gaddis’s view, ‘a closer look suggests that the threat of nuclear annihilation deserves little credit for the Long Peace.’ If it were shown that ‘the Long Peace was a nuclear peace’, Pinker remarks, this ‘would be a fool’s paradise’, because of the ease with which a miscommunication or accident could ‘setoff an apocalypse’. His look was not close enough, as the case against the coercive peace is inadequate. Moreover, when we consider the normative basis for the Long Peace, as applied to nuclear weapons (the ‘nuclear taboo’), it exposes the problems of relying on normative restraints. The problem with a coercive peace is not that it is a myth but that it cannot be expected to endure indefinitely.

The Second World War’s finale involved the first deployment of nuclear weapons in anger, with the destruction of the Japanese cities of Hiroshima and Nagasaki. Since then, there have been crises in which there were fears that they might be used again and defence policies that have given a central role to nuclear threats. Although further nuclear use has been avoided, the same combination of technical safeguards and political common sense may not get us through the next seventy years without a disaster of some sort. Nonetheless, the record to date undermines the claim that the only alternative to complete disarmament is complete disaster. If that had been the case, we have no right still to be around. Instead, considerable caution has been introduced into statecraft as a result of the unambiguous awfulness of the weapons. Over time, countries have come to adapt to their existence and, as a result, a sort of nuclear order has been created, with a degree of underlying stability. This means, however, that avoidance of a terrible conflagration depends on a daily act of restraint. Even when governments feel a need to remind others of their nuclear capabilities, we must rely on them keeping their arsenals under tight control and not getting close to ordering any strikes. The fact that a range of governments, totalitarian as well as democratic, vulnerable as well as confident, anxious as well as relatively secure, have managed this restraint over a number of decades is at least evidence that they understand the risks. They have been reluctant to allow a minor event to trigger a rush to war, or to accept that all inhibition can end, and prudence be forgotten as soon as fighting begins. If the First World War had dashed confidence in the old balance of power, which relied on individual states acting to keep the system in a form of stable equilibrium, the nuclear age helped revive it. In one of his last speeches as prime minister, Winston Churchill commented on the ‘sublime irony’ that a stage had been reached ‘where safety will be the sturdy child of terror and survival the twin brother of annihilation’. It was hardly comfortable to rely on a balance of terror to keep the peace but, overtime, as the condition of mutual assured destruction was recognised, it appeared to work.

A number of abolitionists have sought to deny that there has been a valuable deterrent effect. Ward Wilson, for example, argues that with proof that nuclear deterrence does not work, the case for disarmament is sealed. Without a ‘stronger rationale for keeping these dangerous weapons’, he wrote in a 2008 essay, ‘The Myth of Nuclear Deterrence’, then ‘perhaps they should be banned’. He went so far as to insist that the atomic bombing of August 1945, played no role in Japan’s surrender, suggesting that the real cause was the Soviet Union’s entry into the war against Japan. This is a dubious claim but can be addressed by reference to the historical evidence. With regard to later deterrent effects, the analysis is even harder because that requires working out conclusively why nothing happened. Ward’s method is to cite cases in which something happened to a nuclear power and to mark that as a failure of deterrence. Thus, he points to America’s two wars with Iraq (1991 and 2003) and NATO’s with Serbia over Kosovo in 1999; Britain and the Falklands; and Israel and the 1973 Yom Kippur War. This is poor methodology. In none of these cases was any attempt made to deter, to control events using nuclear threats. There was no reason to suppose that the weapons were in play. The parties to the conflict did not act as if they were. The only possible exception is the 1973 Yom Kippur War. Israel had made no attempt to use nuclear threats to deter Arab invasion because it was confident in its conventional forces, but as Arab attacks began to make progress, the nuclear issue did begin to come into view. In the event, the Egyptian and Syrian armies were pushed back without resort to explicit nuclear threats. At the end of the crisis, there were reminders of high nuclear stakes as the Israelis surrounded the Egyptian Third Army.

Pinker uses a similar method to Wilson. Thus, he finds it telling that Britain’s nuclear capability did not prevent Argentina invading the Falklands in 1982. The Argentinian junta ‘ordered this’, he says, ‘in full confidence that Britain would not retaliate by reducing Buenos Aires to a radioactive crater’. In fact, they launched the invasion confident that Britain would not do anything militarily at all. They had ruled out a British military response in their planning. For its part the British government had not made any attempt to deter the junta because the British government did not realise that the junta needed to be deterred. As news came in that an invasion was taking place, the British government discovered, somewhat to its surprise as well as Argentina’s, that it could send a credible task force to the South Atlantic. This approach, therefore, gets the issue the wrong way round. It is not whether wars take place despite the existence of nuclear weapons, but whether some wars did not happen, or were limited, because of their existence. It is not whether Syria and Egypt discounted the risk of a nuclear riposte to a limited war in October 1973, but whether they understood that this risk could grow if Israel began to face a truly existential threat and whether this affected their readiness to come to amodus vivendi, just as in 2002, India and Pakistan stepped back from a full-scale confrontation as they became aware of where this might lead.

The risk of retaliation was the source of prudence and the basis of deterrence. Anything that might challenge the possibility of retaliation put deterrence at risk because it might render threats incredible. Hence the search for a ‘first strike capability’ that might be able to disarm the enemy in a surprise attack and force the defenceless enemy state to capitulate. Such a capability would link nuclear weapons with classical military theory and the search for a knockout blow. A battle would have been won and the defeated state would be at the mercy of the victor. Once, however, the attacked nation possessed sufficient forces to survive an attempted first strike with retaliatory weapons intact, it would have what was known as ‘second-strike capability’ and prudence would be in order. A first-strike capability offering one side a decisive advantage risked a dangerous edginess developing at times of crisis and even leading to a catastrophic war through miscalculation. If there was no premium in a first strike then both sides should be more cautious and concentrate on diplomacy in a crisis. The calculations of risk might shift very quickly, especially if both sides had sought a first-strike capability. On the other hand, if both sides were confident of their second-strike capabilities, there would be no premium attached to unleashing nuclear hostilities. In the event, technological developments supported the second strike. By the mid-1960s, it was apparent that, for the foreseeable future, each side could eliminate the other as a modern industrial state. The term chosen to describe this condition, mutual assured destruction, conveyed exactly what it was supposed to convey — destruction would be assured and mutual. Contrary to what had been assumed, therefore, the system tended towards stability. This was not a deliberate policy choice but a condition which confirmed the risks involved in any attempt to achieve a decisive victory through a knockout blow.

There was a paradox. Deterrence required that military preparations be taken seriously, accepting that the prospect of war, even if tiny, was still finite. All this made the task of designing, constructing and sustaining armed forces extremely difficult. It was hard to think through the circumstances that would trigger a war in the first place. So potent were the nightmarish images of a third world war that there really was no good reason why any moderately sane leader would start one deliberately. That helps explain the coercive peace. But others have also argued for the normative nuclear peace, that political leaders have become inhibited from contemplating nuclear use because this would be an appalling thing to do as can be seen in references to a ‘nuclear taboo’ or, in Nina Tannenwald’s phrase, a ‘norm of non-use’. Nuclear weapons are seen to be so exceptional and pernicious that no moral person could contemplate their use.

In The Nuclear Taboo, Nina Tannenwald argues that the taboo takes restraint beyond deterrence. There may be no fear of retaliation, but nuclear use still seems to be unthinkable. She places considerable weight on anti-nuclear movements as a source of the taboo. Yet to the extent that these movements prospered during the Cold War (they have been largely absent since), it was because they were playing on general unease about the implications of such huge power. The idea of a ‘taboo’ was first raised during the 1950s in connection with ‘tactical’ weapons and not the new thermonuclear city-busters and, then, as a worry rather than a relief. The American government was concerned that this would prevent it from taking advantage of its most effective weapons because of a fear of Soviet retaliation. As it became evident that it was meaningless to speak of a victory in any nuclear battle, the ‘nuclear taboo’ came to refer to a sort of institutionalised common sense, reflected in a desire to avoid any situation in which their use might be contemplated.

There are other reasons. Over time, the military purposes that might justify any resort to nuclear weapons have narrowed. During the early stages of the Cold War, they were the only means of destroying some targets. This is no longer the case, because of the accuracy and lethality of conventional munitions. Claims that alternative forms of mass destruction, such as biological or chemical weapons, could only be deterred by nuclear weapons do not withstand scrutiny, although the formal NATO position is that this is a possibility. If such weapons were used, there would be a variety of possible responses in a government’s repertoire short of inflicting some great punishment against civilians. So the routine expectation of the first decades of the nuclear age, that one way or another any future hostilities between nuclear-armed states would escalate to nuclear use, and that escalation would take over as one mega-explosion led to another, may no longer be valid.

At the end of the Second World War, after the Holocaust, carpet-bombing and V-missiles, the atom bombs seemed to be a logical culmination of what had gone before and also brutally successful in bringing a total war to an end. The simplest, if depressing, assumption was that war had become progressively more murderous, with ever more sophisticated means being found to slaughter people on a large scale. There was no reason to suppose that future wars would not follow the trend. The trend in conventional war since 1945, however, at least in the West, has been to seek more ethical strategies that deliberately avoid civilians and refrain from the sort of raids against centres of population that both sides employed during the Second World War and in later campaigns, such as Korea.

In part, this is because of revulsion at the consequences of city-bombing; in part, it is because of a view that, even at its height, the strategic effects were limited as societies absorbed punishment in preference to surrendering; in part, because targeting has reached levels of precision unimaginable in the past. We have reached the point where the expectation is that only the intended target should be hit and any collateral damage is unacceptable. This could change. Perhaps under the strain of war, attitudes could switch, as they have switched before, into a position where the old arguments about getting at governments through their miserable populations will appear credible again. There may simply be a visceral desire for retribution. We can see that Russia has made regular reference to its nuclear capability since the start of its intervention in Ukraine, presumably to persuade NATO to stay clear. At the same time, the fact that it has picked on Georgia and Ukraine, neither members of NATO, but only made menacing noises to countries such as Estonia, a member of NATO, demonstrates that deterrence is far from irrelevant

A social or moral constraint is not the same as a physical constraint. The experience of war will test any taboo. Soldiers can be recruited into an army, have the rules of war explained to them, find the idea of harming innocents repugnant, yet as circumstances change and the conflict becomes more intense, they find themselves engaged in those very acts that would have horrified and shamed them not long before. This can also happen at the governmental level. The international system is one in which individual states are not subject to any higher authority and norms are not universally shared. At desperate moments of existential threat, in a country battling against overwhelming military odds, concerns about breaking taboos may suddenly become less pressing. A number of restraints were in place at the start of the Second World War, including proscriptions on the use of chemical weapons, attacks on merchant shipping and bombardments of civilian populations. Only the one on chemical use held. They all came under pressure as the war became more total. Thus the war did not open with air raids against cities, as many had feared, but soon cities in the way of invading German forces were attacked. It took almost a year before air raids against large centres of population began to become common. They initially reflected notions about how popular morale could be a legitimate target to undermine war production. They then came to reflect a lack of alternative options and a yearning for revenge. By the end of the war, with the allies having freedom of the skies, bombing was progressively unrestrained, concluding with the systematic fire-bombing of Japanese cities and then the use of the two atom bombs. Political leaders were authorising actions by the end of the war that would have appalled them at the start. The taboos did not last.

Thus, a point can come during the course of a conflict when the unthinkable becomes possible. In a war of growing brutalisation and intensity, the pressures would build so that the most devastating weapons available would be used, even nuclear weapons, regardless of the consequences. We do not need to doubt that the nuclear taboo has been internalised to worry that the effect might ease during the course of a war of increasing intensity and violence. This prospect might well influence crisis behaviour. Imagine a crisis in which the leaders of one nuclear state observed that the risks of a major war with another nuclear state leading to mutual destruction were negligible because the taboo was in place. This would seem alarmingly complacent. The danger, these leaders would quickly be warned, lies not in what has been said before, but what might happen should the crisis get out of control. Even if nuclear threats are becoming less credible, the possibility of a catastrophic miscalculation remains, especially in a social and political setting already transformed by brutalising violence. Because nuclear weapons are dangerous, prudence dictates considerable caution when moving towards any situation which could create pressures for their use. This is why nuclear weapons can have a deterrent effect well beyond their logical limits. There is therefore no reason to view the normative restraints surrounding nuclear weapons as an alternative to prudential deterrent effects. It is good to have a normative peace, but it needs the backstop of a coercive peace.