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Maximum Stockpiles and Minimum Deterrence

This essay was first published in October 2021, in the second volume of the Centre for Defence Studies series on The Integrated Review in Context: Defence and Security in Focus.

Ever since NATO’s September 2014 Wales Summit, which re-stated its 2 per cent guideline on Defence spending as a proportion of Gross Domestic Product, it has been necessary tediously to repeat that that figure is “a floor, not a ceiling”. In other words, it is “a minimum, not a target”. Now we face a similar task regarding the increase, recently announced, in the cap on the size of our nuclear stockpile. That cap should be described as “a ceiling, not a floor”. In other words, it is “a maximum, not a target”.

The Integrated Review of Security, Defence, Development and Foreign Policy, relates how: “In 2010 the Government stated an intent to reduce our overall nuclear warhead stockpile ceiling from not more than 225 to not more than 180 by the mid-2020s. However, in recognition of the evolving security environment, including the developing range of technological and doctrinal threats, this is no longer possible, and the UK will move to an overall nuclear weapon stockpile of no more than 260 warheads.”

Predictably, this is being denounced as a more than 40 per cent increase in the stockpile – on the basis that increasing a total of 180 to 260 would be an uplift of 44.4 per cent. Yet, the cancellation of a reduction which has not yet been completed (if, indeed, it ever began) means that, at most, the total might rise from the previously declared maximum of 225 to a new maximum of 260. Were those the actual present and future totals, the increase would be only about 15.5 per cent – a perfectly reasonable increment to ensure that advances in anti-ballistic missile (ABM) technology, over the 40+ years of our next generation of Trident warheads, cannot undermine our policy of minimum strategic deterrence.

Minimum deterrence relies on the fact that possession of a last-resort strategic nuclear system, which can be guaranteed to inflict both unacceptable and unavoidable devastation in response to nuclear aggression, does not require any ability to match the aggressor missile-for-missile or warhead-for-warhead. – Dr Julian Lewis MP

Nuclear superpowers have huge overkill capabilities which offer zero extra protection against countries with much smaller WMD arsenals – as long the latter can retaliate with an unstoppable and unbearable counterstrike against any nuclear aggressor seeking to wipe them out. Overkill capabilities may have symbolic political value, but – in the dread event of a nuclear exchange – all they can do is to “make the rubble bounce”.

There may exist more up-to-date estimates, but SIPRI’s inventory totals for world nuclear stockpiles, published at the beginning of 2020, are sufficiently instructive. China, France and the UK, with estimated warhead totals of 320, 290 and 215 respectively, fall into the camp of minimum strategic deterrence. By contrast, the estimated totals of 5,800 for the United States and 6,375 for Russia, go way beyond anything needed to pursue such a policy. This still applies to the considerably lower totals (thought to be 1,750 for the US and 1,570 for Russia) of nuclear warheads actually deployed.

The notion that, at some stage in the future, the UK might end up with 35 more warheads than its previously declared theoretical maximum, does not change the fact that

we are currently, and shall probably remain, fifth out of five in terms of the size of the nuclear stockpiles held by the permanent member-states of the UN Security Council. – Dr Julian Lewis MP

So, why has the Government chosen to take the controversial steps of cancelling the reduction in the “ceiling” of our warhead total from 225 to 180, and raising it to a new ceiling of 260, instead?

Here are the four possible explanations which occur to me, in the absence – at the time of writing – of any briefing on this issue, classified or otherwise, from my Parliamentary colleagues on the Defence Ministerial team:

  1. Most probably – as already stated – it is as an insurance policy to prevent a potential aggressor from calculating that advances in ABM systems had reduced our retaliatory capability to a point where our response to an attack became bearable or even avoidable.
  2. Quite probably, it is to give more ‘headroom’ for the time – in the late 2030s or early 2040s – when we are due to exchange our current stockpile for next-generation nuclear warheads, whilst at the same time preventing disruption of our Continuous at-Sea Deterrent patrols.
  3. Possibly, it is to send a signal internationally that the UK is determined to keep nuclear weapons as long as other countries have them, and remains committed to doing whatever is required to maintain their invulnerability.
  4. Conceivably, it is also tailored for a domestic audience worried about cuts in the size of the Army, in order to offer reassurance or at least divert some attention from those reductions.

What seems most unlikely is an intention to invest in additional warheads of the existing design. We are certainly cancelling their reduction from a theoretical maximum of 225 to one of only 180, for any or all of the four reasons listed – particularly the first one. Raising that maximum from 225 to 260, to provide extra ‘headroom’ for the eventual transition from current warheads to their replacements, is a sensible explanation – though not a conclusive one, given that the changeover is not due to happen for well over a decade.

Whenever questions arise about the continuation or renewal of the UK’s strategic minimum nuclear deterrent, vociferous opponents make themselves heard. They remain, nevertheless, in a minority both outside and within Parliament. Over many years, numerous opinion polls yielded strikingly consistent results: about one-quarter of the population favour British unilateral nuclear disarmament, whilst just over two-thirds wish us to keep the deterrent as long as other countries possess nuclear weapons. These opinions proved decisive, not only in the landslide Labour defeats of 1983 and 1987, but also in Labour’s subsequent determination not to propose nuclear unilateralism in any future General Election.

Despite the imposition of a dedicated supporter of the Campaign for Nuclear Disarmament, Jeremy Corbyn, as their Leader in 2015, Labour MPs ensured that party policy remained multilateralist. Previously, on 14 March 2007, Parliament had voted by 409 to 161 in favour of proceeding with the “initial gate” for renewal of the Trident submarine fleet. Even that huge majority of 248 was eclipsed, on 18 July 2016, when it rose to 355 after MPs voted for the decisive “main gate” stage to proceed, by 472 to 117.

Then, as now, Article VI of the Non-Proliferation Treaty was prayed in aid by opponents of the British deterrent as if it committed all the signatories to nuclear disarmament separately from other forms of disarmament. It does no such thing. The preamble to the treaty states that nuclear disarmament should occur “pursuant to” (that is, in conformity with) “a treaty on general and complete disarmament”. Article VI similarly commits the signatories “to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control” (my italics).

The size of Britain’s minimum deterrent warhead stockpile has never been related to the size of any adversaries’ arsenals.– Dr Julian Lewis MP

The sole determinant is that we must still be able to threaten unacceptable and unavoidable retaliation throughout the lifetime of the Trident system, catering for the potential development of countermeasures during this long period. If that does require an actual increase in our warhead stockpile of up to 35 extra warheads, it in no way contravenes the provisions of Article VI of the NPT. We are not, and never have been, involved in a nuclear arms race with any other nuclear state. Neither, for that matter, is France nor (so far) is China. Minimum deterrence does not require thousands of warheads to fulfil its function.

There is nothing in Article VI which requires a nuclear-free world to be achieved before general and complete conventional disarmament can also be guaranteed. There is a very good reason for this: abandoning all nuclear weapons in an un-reformed world would be a recipe for disaster. In a conventional war taking place in a nuclear-free world, the former nuclear powers would immediately race to reacquire the bomb. The first to succeed would then use its monopoly, as occurred in 1945. If the treaty’s vision of general and complete conventional disarmament ever becomes reality, then nuclear weapons can also safely be declared redundant. Until that day dawns, the United Kingdom is perfectly capable of changing the size of its warhead stockpile without breaching the NPT, in order to maintain indefinitely the credibility of its strategic minimum deterrence policy.


Dr Julian Lewis is the Conservative MP for New Forest East. Dr Lewis was chairman of the House of Commons Defence Committee, 2015–19, and is the current chairman of the Intelligence and Security Committee of Parliament. He writes here in a personal capacity.


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