Making a Mess of the Moscow Criterion - British Nuclear Policy in the 1970s

 

One of the great strengths of the British system of Government is that it is able to see documents declassified and released through to the National Archives at Kew. This priceless repository of knowledge houses many files, both physically and electronically which are cleared for public release.

Some files emerge in a blaze of glory, covered in the media ahead of time and are of keen public interest. Others slip quietly into public access, with little mention of their existence, and often lurk online for months or years before being spotted. 

One such document is about the Chevaline programme (CAB-301-734) , a major update to Polaris in the 1970s, which on closer examination reveals a fascinating story of how the British Government became increasingly reliant on the US for nuclear support, and nearly scrapped its nuclear deterrent.

Image by Ministry of Defence; © Crown copyright

The British nuclear submarine-based deterrent initially came into service in the late 1960s, providing ultimately 4 ‘RESOLUTION’ class SSBNs, each carrying 16 Polaris missiles, with 3 warheads, intended to deter aggression by the Soviet Union.

The power of the Polaris system was that unlike fixed airfields and other sites, it was practically invulnerable to a first strike attack, and could exist to threaten to wipe out Moscow and other major Soviet cities if required, even after the UK had been obliterated in a nuclear attack.

In theory the UK nuclear deterrent was committed to NATO – and would be employed alongside other NATO nuclear weapons if called upon as part of an integrated strike which would involve all out nuclear release. This was the main role for the force, but in addition it could be, in theory, returned to national control and used to conduct a unilateral nuclear strike if British national survival was under threat.

The criterion that the UK used to determine its threshold for nuclear strikes in the latter category drove nuclear planning in the 1960s and 70s. The challenge was how to ensure that in the event of a unilateral nuclear attack, British warheads could be reasonably certain of holding Moscow at risk, and being able to penetrate the ‘anti-ballistic missile’ (ABM) systems around the city, intended to protect it from attack.

A NATO strike would have seen literally dozens, if not hundreds, of nuclear warheads being targeted on Moscow, wiping the city out in a vast cacophony of nuclear blasts. But a British solo strike would have been more complex – in a ‘bolt from the blue’ scenario, where the UK found itself with only one nuclear submarine on patrol, there would be only 16 missiles available to fire, and no support from allies, would this be enough to destroy Moscow in isolation?

This problem – the so-called ‘Moscow Criterion’ defined how the UK would tackle the challenge of Cold War nuclear planning – the assumption was that the deterrent would only work on a policy level if the Soviets planned on the assumption that the UK could overcome any credible defences and wipe out their main cities.

Even as Polaris entered service it was clear that this was very quickly not going to work as a plan – the missiles range was short and they were incapable of carrying enough warheads to overcome the potential city defences. By 1968 the UK had introduced improvements to the Polaris missile known as the ‘super antelope’ which was assessed to provide a credible deterrent capability.

The Royal Navy quickly pushed to step away from Polaris, and instead purchase the more powerful Poseidon missile, which was then entering service. According to the files, the Naval Staff pushed for the purchase of this missile on at least 4 different occasions between the late 1960s and mid 1970s, (1968, 1970, 1972 and 1974) without success.

Instead the decision was taken to invest in an update programme to the Polaris missile involving refitting it with an entirely new ‘front end’ that would provide a complex range of decoys, balloons and nuclear warheads that would manoeuvre after launch to simulate incoming missiles to minimise the risk to the actual warheads, and maximise the chance of their penetrating Moscow and destroying it.

The programme became known as ‘Chevaline’ and was conducted in the utmost secrecy, trying to develop and deliver a credible strategic nuclear deterrent for the 1970s and 1980s. Parliament was not informed about the programme for many years after it began, raising accusations of secrecy.

The problem that Chevaline soon experienced was that it was not only extremely technically challenging, but it also raised significant safety risks too. The files reveal in significant detail that the Royal Navy was extremely concerned about the proposed upgrade plan, noting that it would involve putting a liquid fuelled top stage of the missile on top of a solid fuelled missile. This raised very large safety case concerns for the RN, which was worried that the risks of explosion onboard an SSBN could be much higher than for inert solid fuel, and potentially cause the loss of an SSBN on patrol.

By 1974 the debate focused on whether there was a credible risk of explosion from the liquid fuel, or if this was manageable This risk led to the beginning of a major policy debate in the very heart of the secret state about whether this was an acceptable level of risk, or if there were alternative options open to consider.

There appears to have been a difference of opinion between different parts of government on what the right answer was in this case. To the Royal Navy, charged with delivering the nuclear deterrent mission, the only acceptable answer was to step away from Chevaline and Polaris and upgrade to Poesidon as quickly as possible to maintain the credibility of the deterrent.

By contrast No10 was growing increasingly frustrated with what it saw as an inability by the Royal Navy to focus on delivering a capable SSBN force, and its constant demands to goldplate the solution – in one memo to the Prime Minister from his Private Secretary there is the line:

“one had hopes that the Navy would settle down into whole-hearted acceptance of the chosen system and in getting the British strategic deterrent into service as quickly and economically as possible. This still does not appear to be proving the case, and one has to explore why”

The Royal Navy appeared to have its heart set on better missiles to deliver the deterrent mission, and seemed to be doing everything possible to force the issue. This led to growing mistrust of the RN’s intentions – to the eyes of No10 it seemed to be beyond risk averse, and seeking every opportunity to play down the credibility of Polaris and Chevaline safety to instead get better missiles.

The files show the clear tensions – those charged with delivering the nuclear mission were seen as being obstructive on the grounds of being concerned over the chance of a highly unlikely set of occurrences posing a risk to the nuclear mission. But, arguably the credibility of maintaining the deterrent at all times calls for as low a risk as possible in order to ensure that the mission succeeds – to intentionally increase the likelihood of politically mandated risk poses a wider challenge to the delivery of politically mandated policy.

This leads to an interesting question on the level to which ‘risk acceptance’ is something that is for the military to define, or for politicians to set. There is no right answer here, but the sheer level of tension is palpable through the files.

The outcome of these risk concerns led to a major discussion in the UK Government about what to do – the realisation was that one option would be to accept the risk and ‘crack on’, while another would be to move to a solid fuel-based system. The problem here was that the UK had no equivalent solid fuel system in existence – this therefore led to a discussion in the mid-1970s about how the British Government could persuade the US Government to provide access to Trident missile technology, to help power the penetration aid compartment (PAC), in order to reduce the risk further.

This led to the incredible situation emerging of correspondence between senior officials on the lobbying strategy that would be employed to the US on persuading them to allow the UK access to this technology. It is in a way astonishing that foreign Government officials knew more about British plans to upgrade their nuclear deterrent several years before Parliament did.

It also highlights the increasing debate that the UK had to have in the 1970s between accepting risk, and accepting dependency on another nation for critical support. To bring US technology in to the Chevaline system would increase its safety, but would reduce UK control over the missile, and leave the UK ever more reliant on the US for support well into the 1980s.

But if they retained liquid fuel – the risk to the overall safety of the programme was threatened – what was more important – was it national sovereignty, or was it the safety of the deterrent against risk?

There was a significant debate within Government over what to do – the Royal Navy was concerned that the risks posed by liquid fuel could, if not resolved, pose an irrecoverable problem to the Chevaline programme that would prevent it from being delivered – if it were found late in the day that liquid fuel did not work, then the UK strategic nuclear deterrent would be fatally undermined.

To resolve this would require taking out the ‘insurance policy’ of a solid fuel option based on Trident missile technology, which the papers make clear was only on offer if the UK made a personal approach to the US Secretary of State for Defense. The risk here was both a significantly higher cost (a near 10% cost increase in the programme), potentially with nothing to show for it if the UK liquid fuel system worked.

This is where we see Ministers facing difficult decisions – do they overrule the advice of naval professionals and rebuff the approaches to the US, knowing it threatens the long term credibility of the deterrent – or do they make the approach ,and risk spending a lot more money without being clear it was actually needed – and to do this at a time when the Chancellor (Dennis Healey) was noted in HMG papers as being keen to cancel the entire programme on cost grounds.

This challenge led to an internal debate within government on what to do over the Polaris problem. Was it appropriate to continue with Chevaline, even accepting the risks it posed? Should the UK look to develop an alternative missile option that would downgrade the cost and risk of the project, but reduce the overall deterrence posture – for example to not hold Moscow at risk? Alternatively could the UK even look to get out of the nuclear game altogether?

The papers that have made it into the public space are redacted but still offer a fascinating insight into where Government and military thinking was on the subject by the mid-1970s.

There appears to be a significant divergence of policy views between the Politicians and the military on what was the most appropriate course of action. It appears that serious consideration was given around 1975 to continuing to develop Chevaline, or to look to develop several lower cost alternatives with different penetration capabilities.

The specifics of the variants remain redacted and highly classified, although one note from the Secretary of State for Defence suggests that at least one would have scrapped the penetration aids, and instead relied on hardened warheads and greater dispersal of their firing to maximise survival chances to strike Moscow.

In a lengthy minute, huge chunks of which remain redacted, the criteria for British nuclear deterrence credibility versus the options on offer was considered. We do not know what these criteria were, save that the authors noted:

“Both the Americans and the Russians would continue to judge us as a serious independent strategic nuclear power only if they too judged that the criteria implied in paragraph 7 were adequate for an ultimate national deterrent and so long as we could continue to meet them”

In other words, British nuclear policy was governed, in part at least, by the determination of British policy makers to ensure that both Russia and the USA viewed the UK as a serious independent nuclear power capable of launching a credible nuclear strike.

This is a telling insight into British thinking of the 1970s – it seems to indicate that Paragraph 7 (presumably the ‘Moscow Criterion’) sets out what British nuclear forces needed to be able to do in order for the Russians and US to take Britain seriously as a nuclear power.

For Moscow this would be to consider that the British deterrent was credible as a threat to Moscow, while to the Americans it was presumably to ensure that the UK was seen as a partner, not merely a ‘dual key’ ally. The importance of being seen to be credible in the eyes of the USA seems as important a fact of the Moscow Criterion as the ability to deter the Russians.

The result was an annex setting out the various options that could be considered and the potential impact of the measures when set against the need to destroy Moscow. The assumption made by military planners was that Moscow would be defended by potentially up to 100 ABM’s, which would try to wipe out an incoming nuclear strike.

The assessment was that continuing with Chevaline would ensure that by 1980, the UK would be able to ensure that with 2 boats available, the UK could be certain of getting a variety of missiles onto the target.

It was assumed that an undefended Moscow would be hit by 16 warheads from a single SSBN, while if Moscow was defended by 100 ABMs, only 1 missile would get through in the worst case, but potentially up to 39 warheads.

The number decreased depending on Russian defence measures, but it seems reasonable to assume that the Moscow criterion was designed to assume that British nuclear policy was built on the assumption of hitting and destroying Moscow with somewhere between 16 and 39 nuclear warheads in the event of an independent attack.

Whether nuclear targeting policy ever called for a strike involving that many missiles on one city is unclear and unlikely ever to be known. But it is clear that British policy was built around building a very credible ‘worst case bad day and still being able to completely destroy your capital’ plan, because they knew that if the Russians and Americans thought the UK could not do this, then the UK would cease to be a credible nuclear power in their eyes.

The other options under consideration ranged in outcomes from assuming that different variants would have later entry to service dates but higher missile penetration, or retaining the existing system.

Other notes relating to these studies suggest that to make the project affordable and reliant on variants required changing the requirements for nuclear deterrence away from being able to respond at any time to a ‘bolt from the blue’ scenario to a very different set of circumstances. It is unclear what this means, but it is also clear that this would have radically altered British defence policy assumptions.

The analysis of retaining Polaris ‘as was’ without any improvement indicated that if left unimproved, by the early 1980s, there would be no chance at all of any British nuclear warheads being able to penetrate Moscow and destroy it.

This then leads us to a fascinating debate – was it the right thing for the UK to not spend the money on Polaris upgrades and retain a strategic nuclear deterrent in name only? In other words to retain the SSBN force with minimal expenditure, knowing though that it would only be used in the event of a NATO attack on Russia?

Would doing so, knowing that British missiles posed no threat to Moscow, but could hold many other Soviet cities at risk be a sufficiently credible deterrent to ensure that Soviet planners factored this into their calculations? Or would it do damage to British standing – the assumption in the papers was that Moscow would find out about the loss of British nuclear credibility. In that case, would they feel more bold taking on NATO, and the UK knowing the reduced nuclear threat they faced?

At the same time, how would the US sit knowing that the UK, a nuclear partner on paper was actually not credible in reality? From a strategic ambiguity perspective, one of the strengths of NATO in the Cold War was that with two-three different nuclear powers in the Alliance, Moscow could never be certain how they would react in the event of an attack.

If Moscow knew that only the US was a credible nuclear power, this could open the door to all manner of new calculations – could the Russians split the US from European NATO, or try to say that in the event of conflict, they would not use strategic nuclear weapons if the US did not – suddenly Europe could become a nuclear battlefield, with Moscow and Washington safe, and safe in the knowledge that the UK could not hold Moscow at risk.

This sounds faintly perverse, but it highlights the challenges of deterrence policy in the Cold War – British politicians had to consider what was the most pragmatic course of action – maintain a credible deterrent, or maintain a deterrent in name only.  Indeed at one point in the discussion, it was noted that if the UK retained Polaris without modernisation, was it worth retaining it at all, or was it better to get rid of it entirely?

Nuclear deterrence was cheaper than conventional deterrence, and less likely to lead to conflict – at a time of major fiscal challenges, was it better to spend on high tech investment in projects like Chevaline, or scrap it and invests in significant upgrades to the conventional forces, with commensurate loss of influence and access in NATO as a less credible partner than before?

The decision in favour of Chevaline seems to have come down to a wider game of assessing that the Soviet Union would be constrained by wider strategic arms reduction talks. The SALT talks of the early 1970s limited US and Soviet deployment of ABM’s, and the British assessment was that even if the Soviets could guess how the UK would deploy its nuclear deterrent, the constraints of the SALT Treaty would make modernising the ABM system to cope with the challenges of Chevaline unfeasible:

“We calculate they could not defeat Chevaline without making major and costly improvements to their defences which could not, so far as we can foresee, be contained within the limits of the 1972 Treaty”.

This illustrates the fascinating dependency that the UK had in the 1970s on US nuclear policy – to ensure that the ‘Moscow Criterion’ was credible, the UK needed to ensure that the US/USSR nuclear balance of power was effective. If SALT had collapsed and the Russians had no further constraints on their ABM capability, it paradoxically would have probably made the British independent deterrent worthless as a risk to Moscow.

This in turn raises interesting questions about the level of British concern some decades later at the US withdrawal from the ABM treaty, and whether this would in turn lead to Russia developing ABM measures that could render the Trident deterrent worthless…

Amid all of this debate what was particularly fascinating was the split in opinion between the Military as to what the right answer was. According to minutes at the time, CDS favoured proceeding with Chevaline, while the Navy was keen to explore variants, while the other services were minded to support Chevaline and not the variants. It appears that the Navy, having realised the economic impact of Chevaline on its own budget (as well as the risk) seemed far less keen to proceed with it than other parts of the system.

The outcome though was a decision by politicians to proceed with Chevaline, and ignore the RN request for solid fuel technology. Ministers at the time decided to proceed with the upgrade, deciding that the value of maintaining a nuclear deterrent that was credible to allies and foes was more potent than other options.

This sums up the difficult decisions facing politicians in a time of financial crisis – do you spend money on nuclear weapons, knowing that you never wish to use them, but have their readiness and credibility exist as a sign of how serious the UK was about deterring Russia, or do you spend the same money on conventional forces that may not deter, but which could reduce the chance of a conflict getting to the nuclear stage.

Arguably British defence policy of the period appears to have been built around trying to appear credible in the nuclear game, in the hope that the bluff would not be called in the conventional space. It is also telling that the Chancellor wrote an ominous letter to the Prime Minister warning that as Chevaline were to proceed, substantial savings would be required in the conventional military to afford it.

There are two final areas of interest from these files. The first is that there was a significant lack of trust between No10 Downing Street and the Royal Navy in this period. This ties into wider files on other operations, such as submarine based intelligence operations in the 1970s where the Callaghan administration repeatedly expressed frustration at the way the RN refused to engage properly with it.

There seemed to be real concern that the RN of the 1970s was able to constantly change assessments to suit its needs – for example there was deep cynicism from Civil Servants and Ministers over the way that, when it judged it politically convenient to do so, the RN stated that it planned in the 1980s to deploy 2 SSBNs at sea 70% of the time, and planned in wartime to deploy 100% of the SSBN force.

This ‘can do even when we told you we can’t do’ raised concerns, because it suggested that the RN could be less than economical with the truth. Having spent much of the 1960s and early 1970s assessing that they could only deploy one SSBN most of the time without breaking the force, there was unease at the way that the RN suddenly felt that it could change this. The papers suggest a fundamental breakdown in trust between politicians and the military over whether they were being given honest answers.

There was also deep concern at the way that the RN was trying to undermine democratically elected Ministers decisions – at least one minute from the Cabinet Secretary (Sir John Hunt) notes with concern that:

“I have reflected further on how it is that thrice Ministerially approved Polaris improvement programme should still be under challenge from the Navy”…

The last question arising from this file is whether the UK actually had a credible strategic nuclear deterrent for much of the 1970s and 80s – or even if it did not, whether this actually mattered in the greater scheme of things. It does seem that the UK came closer in the 1970s to stepping away from the nuclear game than at any other time in its history as a nuclear power

British policy making in this space was governed on the assumption that to remain credible, in both the eyes of Moscow and Washington, the UK had to be able to be assessed as being capable of destroying Moscow, in isolation and even under a ‘bolt from the blue’ scenario.

This willingness to invest time and resource in meeting the most demanding scenario sent a message on British willingness to use the deterrence in isolation, which in turn reassured Washington and deterred Moscow. But it is also clear that in the eyes of London, Polaris didn’t actually work.

By the mid 1970s there were real doubts that the force as construed could penetrate Soviet defences, and the Chevaline programme continued on for many years past its planned entry to service date. This in turn suggests that between the period 1975 and at some point in the early 1980s when it entered service, the UKs nuclear deterrent was, in policy makers eyes, fundamentally useless.

The realisation that Polaris was going to cease to have any credible deterrent value within a few years meant that when faced with the need to spend a huge amount of money on staying credible, a withdrawal into investing in conventional force enhancements made sense. For financial and technical reasons, the UK possibly came closer to nuclear disarmament in the mid 1970s than we have previously realised was the case.

It is fascinating to consider in hindsight what this means – essentially at one of the most challenging parts of the Cold War, and at a time when difficult decisions were being taken on nuclear rearmament, the Royal Navy was operating a missile system it didn’t want, which could not deliver the mission it was intended to do, and which meant that the UK strategic nuclear deterrent was arguably not worth the paper it was written on, if called on to deliver its ultimate mission.

The UK could still have carried out nuclear strikes as part of wider NATO operations, and left the destruction of Moscow to the USA, but was this an acceptable policy outcome? It will be interesting to see as the years go by and further releases are made into the archives, what assessment was made of the British ability to deliver a truly independent strategic nuclear deterrent.

Why does all of this matter today? Its all very interesting from a historical perspective, but what is the modern relevance of this to 21^st Century Britain? For starters it serves as a timely reminder that Defence is about the management of risk, and that to get deterrence right, there is a need to balance off risk acceptance, versus risk treatment.

There is a constant tension between spending money to ‘gold plate’ requirements or ensure something is over-engineered to survive, and taking a risk that this won’t go wrong. Trying to strike this balance, and deciding what level of risk to accept is key-  should money be spent trying to mitigate the chance of something going wrong, or do we assume that the likelihood of it occurring is so slim, that the mission matters more than the risk?

In a similar vein, there is an ongoing discussion to be had about ‘gold plating’ in general -what is the right level of requirement needed for a defence project and what it has to operate in? Does it make sense to ensure that something can operate in the worst and most difficult conditions imaginable (e.g. a solo British nuclear strike on Moscow) or actually can a similar effect be achieved by other means?

To deliver deterrence effect, do we understand how our perceived enemies view the threat we pose, and their own assessment of risk. Throughout the Cold War, the British Governments view was that destruction of Moscow mattered – but would any Soviet Government be willing to trade off 16 other large Soviet cities in return for a ‘bolt from the Blue’ strike on the UK, even if Moscow survived?

We assumed that Moscow mattered in a way that losing other cities did not – is this right criteria, and is there any assessment on how Russian planners assessed the loss of Moscow vice other cities? We spend a lot of time assuming we understand how others will react to our actions, but do we really understand how others think and interpret our actions in the deterrence space?

In military terms, when looking at new projects, do we overspecify the requirement, and if so, is there scope to scale back? For example does it make sense to build Type 26 frigates capable of the highest level of operating capability, or is this an assessment based on hypothetical risks and challenges that may never be realised?

Finally this debate matters because it highlights the importance of good effective civilian/military relationships. The civilian political decision takers and policy makers need to be able to determine clearly what the effect is that they wish to achieve, and why. The military needs to be able to understand this and what is asked of it to deliver this mission – where this goes wrong is when the policy makers cannot understand why the military are unprepared to accept any risk, because that threatens successful delivery of the mission they are charged to deliver.

Ensuring effective links that join up policy makers and mission deliverers is key here – as we look to the next generation of SSBNs and Trident warheads entering service, there needs to be a clear understanding of what deterrence means, the practicalities of delivering it, and the importance of ensuring that both parties understand what the other wants and expects of each other. A failure to do so creates problems that drive a wedge at the heart of Government with potentially terrifying consequences.