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
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:
- 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.
- The threat is able to be carried out then and there with immediate effect.
- 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.
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
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
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
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
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.