What is Deterrence?

In her statement to the Third International Conference on the

Humanitarian Impacts of Nuclear Weapons, held in Vienna in December

2014, the official uk spokesperson, Susan Le Jeune d’Allegeershecque, told

delegates from 158 other countries that the devastating humanitarian

consequences that could result from the use of nuclear weapons was ‘not

new’ but was indeed the reason why these weapons were so effective as a

deterrent. In fact, the most common response to the humanitarian concerns

raised in the previous chapter is ‘of course nuclear weapons would never be

used, they are merely a deterrent’.1


The uk’s nuclear weapons are not designed for military use during

conflict but instead to deter and prevent nuclear blackmail and acts

of aggression against our vital interests that cannot be countered by

other means… (‘The Future of the uk’s Nuclear Deterrent’ White Paper, 2006)


The British government indeed prefers to refer to its own nuclear weapons,

not as a weapons system at all, but as ‘the deterrent’, as if this categorically

defines what a nuclear weapon is. But a nuclear weapon is not ‘a deterrent’

in and of itself. Even the bbc acknowledges that in its internal guidance

to journalists.2 Any government possessing nuclear weapons hopes these

weapons will act as a deterrent and will never actually be used as weapons.

Whether there is evidence that nuclear weapons have acted as a deterrent up

until now is the subject of following chapters. The question at this stage is

what does deterrence actually mean?


According to the us Department of Defence, deterrence is ‘the prevention

from action by fear of the consequences. Deterrence is a state of mind brought

about by the existence of a credible threat of unacceptable counteraction.’3

In other words, deterrence is a psychological term, not a military term. It is

about trying to create a sense of fear that you hope will convince someone

that they don’t actually want to do something they might otherwise choose

to do.


As a strategy for controlling someone else’s behaviour, deterrence relies on

threatening that person with some form of punishment if they do something

you don’t want them to do. Leaving aside whether coercion through fear is

morally palatable, ‘successful’ deterrence means the punishment never has

to be carried out because the mere threat of it is sufficient to control the

behaviour. ‘Unsuccessful’ deterrence is when the threat has to be carried out

in order to control the behaviour in question.


Deterrence in everyday life

As any parent knows, deterrence as a strategy for controlling the behaviour

of small children is rarely successful – and with older children even less so.

Children are not easily deterred from doing what they want to do at that

moment, even when they know they will have to suffer the consequences

later. When deterrence does (apparently) work as a strategy for managing

the behaviour of children, it normally does so only when:


  1. The actual punishment has been carried out recently enough or frequently enough for the experience of that punishment to be vividly present when the threat is made.
  2. The threat is able to be carried out then and there with immediate effect.
  3. There is no possibility of evading responsibility for the behaviour in question or of getting away with it undetected.


In the absence of these pre-existing conditions, parents find themselves

inflicting punishments to ‘teach a lesson’ for the next time – assuming there

is a next time. Whether or not the subsequent punishment is effective, the

deterrence has clearly failed by that point.


These same principles also apply to the use of (legal) threats to deter

criminals. Deterrence is a well-known, but highly controversial, concept in

the field of criminal justice. Although the primary function of arrest and

detention is to punish criminal behaviour, it is secondarily aimed at deterring

further criminal behaviour. There is an extensive body of evidence to suggest

that people are less likely to engage in criminal activity if they know they

will be caught. However there is an equally compelling body of evidence to

suggest that very few criminals are deterred by the severity of the punishment

they can expect to get, much less by the mere threat of being punished.


Even the threat of death apparently does little to deter murderers. One

has only to compare the murder rates of countries which still have capital

punishment with those which do not to see that the correlation is entirely

opposite to what the theory of deterrence would suggest.4 Almost without

exception, countries with capital punishment have higher murder rates,

higher rates of crime generally, and higher prison populations than those

countries which have abolished capital punishment. This is even the case

within the United States, where some individual states retain the death

penalty while other states have abolished it.


These correlations, it should be pointed out, do not prove that the death

penalty increases the likelihood of murder. However, it certainly does not

provide evidence to support the theory that murderers are deterred from

committing murder or other crimes by being threatened with their own death.

Indeed, reoffending by people who have already served a prison sentence

for an offence is commonplace. In the us, 43.3 per cent of released prisoners

are sent back to prison for another offence. In the uk, some prisons report a

reconviction rate of more than 70 per cent, with an overall national average

of 53 per cent – even higher than in the us.5


What this means for the criminal justice system is beyond the scope of

this chapter. But what it means for deterrence theory is that criminals who

know exactly what it means to be incarcerated for committing a crime

appear nonetheless undeterred by the threat of being incarcerated again.


Military forms of deterrence

Deterrence in warfare is nothing new. The existence of standing armies are

in and of themselves a form of deterrence, meant to warn off any potential

invader by making it clear that the country stands ready and willing to

inflict serious damage on any invading army. All manner of armaments and

fortifications merely add to the deterrent value of being able to threaten

retaliation for any attack.


Switzerland, a country of eight million people surrounded on all sides by

much larger and more powerful countries, was last invaded in 1813. Since

that time, Switzerland has had mandatory conscription for all males aged

19–34 years of age as a deterrent against any possible aggressor.


Although Hitler never invaded Switzerland, it is doubtful it was the

existence of the Swiss Army that deterred him. It is even more doubtful that

the Swiss Army would have deterred an invasion, let alone a nuclear attack,

from the Soviet Union during the Cold War. And yet the Swiss have carried

on with their universal conscription in the belief that they are deterring their

enemies from attacking them.


In 1914, the deterrent that was designed to prevent war in Europe took

the form of a massive network of military alliances that threatened to drag

the whole of Europe into a suicidal war if any one country were so foolish

as to attack another one. The deterrence in that case failed spectacularly

and Europe was quickly locked into a devastating war which took many

millions of lives.


Following the devastation of wwi, the French began construction of the

most advanced set of fortifications ever known – designed to inflict heavy

damage on any advancing armies from Germany and thus hoping to deter

them from attacking. The Maginot Line consisted of 22 underground fortresses,

tank traps, tunnels, rail links and 500 smaller buildings constructed

along the 280 mile border with Germany. One quarter of France’s entire

army was stationed along this line and yet it turned out to be completely

useless against Hitler’s invasion as he simply went around it in May 1940.


The one certainty that can be gleaned from all these examples of real-life

deterrence at all these different levels right up to international war is that

deterrence, even if it may appear to work in some cases, is never guaranteed

to work in all cases. In fact, if history is anything to go by, deterrence is

guaranteed not to work at some point or other.


Nuclear deterrence

The theory of nuclear deterrence depends upon it working not just most of

the time but all the time – and for all time. There is no room for a margin

of error if the consequence of nuclear deterrence not working is an all-out

nuclear war that destroys the whole of human civilisation.


The ‘credibility’ of us nuclear deterrence furthermore rests completely

on the fact that two atom bombs were dropped on Japan more than 70

years ago. While subsequent nuclear tests have shown how enormously

devastating the consequences of a nuclear weapon would be, they do not in

themselves demonstrate a willingness by the us to use such a weapon. The

uk meanwhile has never used a nuclear weapon against another country in

anger. This makes it exceedingly difficult to argue that the uk’s threat to use

a nuclear weapon is a credible one.


This credibility ‘gap’ is a dangerous one when it comes to nuclear

deterrence, because it increases the likelihood that sooner or later a nuclear

weapon will be used, if only to send a clear signal to some future adversary

that the deterrent is backed up by real intention and willingness to use it.


The logic of nuclear deterrence gets more and more convoluted the

deeper one goes into it. It is assumed, for instance, that the leaders of Russia,

in contemplating an attack on the us, would be sufficiently sane and rational

as to weigh up the consequences of a possible retaliatory nuclear strike from

the us and decide on that basis to refrain from attacking. On the other hand,

it is assumed that those same leaders would base their sane and rational

decision on the likelihood of their counterparts in the us acting so insanely

and irrationally as to be willing to launch nuclear weapons against Russia

that would almost certainly bring about their own total self-destruction (see

next chapter on Mutually Assured Destruction).


Furthermore, the theory demands that ‘we’ must be willing to use our

nuclear weapons if necessary and that willingness must be sufficiently

convincing to our opponent that they believe we really will actually use our

nuclear weapons if they dared to attack us. On the other hand, if we are

willing ‘if necessary’ to use our nuclear weapons against another country

which also has nuclear weapons, then at some level we are not ‘deterred’ by

them having nuclear weapons. That other country is likewise not deterred

by the fact that we have nuclear weapons if it is to be believed that they also

would use their nuclear weapons ‘if necessary’ against us.


Ultimately, nuclear deterrence rests on the assumption that no ordinary,

sane person would choose to bring death and destruction down upon family

and friends and loved ones, and would therefore choose some alternative

route other than to invite nuclear retaliation. The problem with this line of

thinking is that nuclear deterrence does not operate at the level of ordinary,

sane people who care about their loved ones. It operates at the level of generals

and politicians who make their decisions according to quite different criteria.

It was the logic of those same generals and politicians who sent millions to

their certain death in the trenches of wwi and authorised the saturation

bombing of German and Japanese cities and the dropping of atom bombs

in wwii.


The actual use of nuclear weapons would cause wholescale slaughter on

an unimaginable scale, but there is no evidence that such a result would

necessarily ‘deter’ generals and politicians from embarking on such a course

should they decide the circumstances ‘justified’ it. Indeed, they have been

ready to launch nuclear war on several occasions and it is luck, more than

‘deterrence’, which has kept us from having a nuclear war up to now (see

Chapter 13).


General MacArthur wanted to drop atom bombs on China during the

Korean War. President Nixon was considering the use of nuclear weapons

during the Vietnam War. Mrs Thatcher apparently threatened to use nuclear

weapons during the Falklands War.6 Plans were readied for the use of nuclear

weapons during the first Gulf War. And as this book goes to print, President

Trump is assembling a vast ‘armada’ of ships, planes and submarines – all

carrying nuclear weapons on board – ready to fire at North Korea in order

to stop North Korea from firing its nuclear weapons at them.


Pressing the button

In her first full speech as British Prime Minister on 18 July 2016, Theresa

May was asked in parliament if she was personally prepared to authorise a

nuclear strike that could kill hundreds of thousands of innocent men,

women and children. Her answer was an unequivocal ‘yes’. ‘And I have to

say,’ she went on, ‘that the whole point of a deterrent is that our enemies

need to know that we would be prepared to use it.’


Nuclear weapons as a ‘deterrent’, therefore, are not somehow distinct

from the intention to use nuclear weapons as a weapon.


In the words of the late Sir Michael Quinlan:

We cannot say that nuclear weapons are for deterrence and never for

use, however remote we judge the latter possibility to be. Weapons

deter by the possibility of their use and by no other route.7

We do not know whether any President or Prime Minister really would

press the button in the event that Russia or another potential opponent

called their bluff and launched an attack anyway. Saying that they would

does not by itself make the threat credible. A Russian leader might calculate

that actually, if push came to shove, a us president wouldn’t actually press

the button even though he said he would. It all comes down to psychology

and there are so many unknowns it is impossible to know what anyone

would do under any number of possible scenarios. That is what makes the

whole theory of deterrence so fanciful.


Deterrence and defence

In the case of nuclear weapons, if and when deterrence ‘fails’, all you can

do is launch nuclear weapons at the other side – or not. In neither case is

anyone being ‘defended’ from attack as such by having nuclear weapons.

This is an important distinction. What would normally be thought of as

‘defence’ are the strategies and resources need to fend off or resist an attack

as opposed to merely retaliating against the aggressor after an attack has

already happened.


During the 1930s, Britain’s air and sea power was strengthened in the

hope of deterring Hitler from invading Britain. When this did not work as

a deterrent, those military resources were used to actually defend Britain from

the impending invasion. The planes and ships were not just a deterrent, they

were a form of defence. Nuclear weapons do not work in the same way. It

would be literally suicidal to start launching Trident missiles at ships crossing

the English Channel, let alone at planes flying over London. Nuclear

weapons cannot defend the uk or any other country even against incoming

nuclear weapons.


If any country were really threatened with attack or invasion by a foreign

power, their only defence against the actual incoming nuclear weapons

themselves would be an anti-ballistic missile system, and even that would

have limited effect. The only real defence against advancing troops or

invading ships are conventional forces, sea defences and other kinds of

fortifications. Nuclear weapons may or may not function effectively as a

deterrent. But if the deterrent fails, nuclear weapons cannot then function

as a form of defence. They are quite literally useless in that sense. While it is

often assumed that somehow nuclear weapons are going to ‘defend’ the

country which has them from being attacked by some other large and

powerful enemy, the truth is they cannot.



The theory of nuclear deterrence suggests that nuclear weapons are so

effective in preventing war that they are unlikely ever to be used. Their

function is to deter aggression, and the more powerfully destructive they

are, the more effective they are as a deterrent.


Deterrence is commonly used as a strategy in all sorts of circumstances

short of nuclear war. In all these other cases, it can be seen that deterrence

is not effective 100 per cent of the time, and can only be effective if the

intention to follow through with the threat is credible, immediate, and

realistic. These same principles apply to nuclear deterrence.


Nuclear weapons cannot be said to act as a deterrent unless there is a

credible, immediate, and realistic intention to use them as a weapon. Thus

it is a contradiction in terms to say that nuclear weapons will never be used

‘because they are only a deterrent’. Nuclear weapons are designed and

deployed as weapons of mass destruction. It is hoped that they will never

be used, but that can only remain a hope.


Successive Presidents and Prime Ministers have claimed publicly that

they would press the nuclear button if the circumstances required it. But

would they? Is it credible, immediate, and realistic that any country would

launch nuclear weapons in self-defence of their homeland, let alone in

defence of some distant ally?


Since the bombing of Hiroshima and Nagasaki, no country which has

had nuclear weapons, has ever used one in war, even when they were on the

verge of losing that war.8 That is not to say that they will never be used,

because the theory of deterrence merely increases the risk that they will be

used. However, the fact that they have not been used so far is not itself

evidence that deterrence has worked. The fact that wars have continued to

be fought and that nuclear weapons have not been used actually undermines

the theory that these weapons are an effective and credible deterrent.