Theresa May says that she would definitely press the button to launch a Trident missile and explode a nuclear bomb, if this country had suffered a nuclear attack.

Jeremy Corbin says that he definitely wouldn’t.

Some further thoughts. The main context of this discussion is the the theory of MAD, or mutually assured destruction.

In order for MAD to be effective, the opponents have to be willing – and committed – to launching their weapons if the trigger condition (as defined) is met. Put another way, there will always be a situation where one of the opponents can reasonably expect that, if A launches an attack, B will respond with a nuclear strike.

Conversely, MAD doesn’t work if various conditions occur. These include the following.

MAD will not work if one of the opponents has foresworn the use of nuclear weapons, ever. There is no mutual threat.

MAD will also not work if one or other of the opponents does not have free and unfettered use of a nuclear weapon.

In the context of the UK and its Trident weapon, MAD may well be, in view of the above, not operative, either actually under May or potentially under Corbyn.

Under May, although she is willing to wreak nuclear destruction, she may not be not a free agent in relation to the use of the Trident missile system, if she needs a ‘second key’ from the USA in order to launch a missile. Unless the USA have previously let it be known to the other side that she is authorised by them to act, her threats are empty.

There is a 2005 response by the Ministry of Defence to a Freedom of Information Act request, (see, according to which the UK does not have to obtain the USA’s prior consent to a nuclear strike. It is difficult to know what weight to place on this. Obviously, if one takes it at face value, then the condition for MAD deterrence is met: Mrs May is willing to strike back, and she is not constrained by the USA in so doing.

But it is possible that the Mandy Rice-Davies doctrine may apply here: ‘[They] would say that, wouldn’t [they].’ To some extent, nuclear deterrence may depend on cardboard policemen. If the opponent believes you have a nuke, are willing and able to use it, your threat will likely be taken seriously. You would not want to bet on it being a bluff – albeit that it might be.

It follows from this that it may not be necessary to spend much on nuclear weapons renewal. For a threat of MAD to work, all you need is a credible chance that your old nuke would get through. Can we offer such a threat, if it rests on a (necessarily unsupported) assertion by the MOD in 2005?

Under a hypothetical Corbyn government, there is no risk of a nuclear strike by the UK, as Corbyn has foresworn the use of nuclear weapons.

If a nuclear threat from the UK may not be credible, why would the not inconsiderable cost of renewing the Trident ‘deterrent’ be justified?

The other thing to observe is that Theresa May appears to be upholding the ‘no first use’ doctrine, although the UK has not made any formal treaty commitment to this effect.

She is saying that there would always be nuclear retaliation if the UK had been attacked with a nuclear weapon. No First Use (NFU) must surely rule out deterrence. The argument is that our opponents would not attack us, because they would suffer nuclear retaliation. It must be doubtful whether, in order to maintain a credible threat to retaliate, one needs to have four submarines.

There would appear to be some illogicality in the NFU argument, because if there is a first strike against us, deterrence will have failed. There will then be no point in our making a retaliatory strike. Again, Mandy Rice-Davies may come to the rescue. ‘Would you retaliate?’ ‘Yes, definitely.’ You would say that, whether or not it was true, in order to maintain the threat. Again, a well-presented bluff might be just as effective – and much cheaper.

Note that these conclusions may be reached without any consideration whether the UK’s opponents in any potential nuclear exchange are identified, or, arguably, identifiable.

Hugh Bryant
20th July 2016