"The Bomber Will Always Get Through" - The Prime Minister and Nuclear Retaliation.

 

The 2024 UK General Election has been held, and a new Government returned. For only the 4^th time in 45 years, there has been a handover of power, on this occasion between the Conservative and Labour party. The new Prime Minister, Sir Keir Starmer MP had, within hours of his election victory assumed office in a peaceful and smooth transition of power, the sort of moment that makes you realise how truly fortunate the UK is to enjoy an election where the outcome is accepted without question or debate. Now that the Prime Minister is settled in No 10 Downing Street, the detailed business of the transition of power has begun. If you believe various media accounts, practically the first thing that happens is that the newly appointed Prime Minister is given a briefing on the nuclear deterrent, a pad of paper and a pen, and ask to discreetly write down their views on what the end of the world should look like. Known as the ‘Letters of Last Resort’ these documents have assumed a near mythological status in accounts of the British State, but are arguably far less important than people perhaps assume…

Trident Submarine © Crown copyright

The UK is a permanent nuclear power, and has been for 70 years. During this time the British nuclear deterrent has been carried on a range of platforms including RAF bombers, intermediate range ballistic missiles and nuclear submarines. It has had both strategic reach, relying on the ‘V Force’ and SSBN force to deliver sufficient warheads to take part in a strategic nuclear strike to wipe out an aggressor, and a tactical reach, including free fall nuclear bombs delivered by shorter range aircraft, depth charges for use at sea and short range missiles and nuclear shells for the British Army in Germany.

The nuclear deterrent has been delivered through purely UK national means (e.g. the SSBN force) and as part of a wider NATO led ‘dual key’ system where US provided warheads operated off UK delivery systems (e.g. Thor missiles). For decades, the nuclear force has been declared to NATO as an asset to be used in collaboration with other NATO partners as part of a deterrent against Soviet attack. The UK has also operated in wider nuclear alliances earlier in the Cold War – for example as part of the SEATO and CENTO treaties, deploying British nuclear weapons to Cyprus and Singapore to support regional war plans. Finally, the UK could, in extremis and as an absolute last resort, deliver a nuclear strike as part of the “National Retaliatory War Plan” (NRWP), a plan which (in theory) would enable the UK to launch a nuclear strike against another nation in isolation and without any allied support.

The specific targets of the nuclear force have always been classified. It is not hard to guess at the theoretical targets, given that British nuclear planning has for many decades relied on the so-called ‘Moscow Criterion’ – namely the number of missiles needed to deliver sufficient warheads onto Moscow to destroy it. The assumption being that if you can destroy Moscow, which is protected by layers of ABM missiles, the Russian key decision makers would realise you could also destroy the rest of the Soviet/Russian state too, and that were they to launch a first strike on the UK, the response would inflict unacceptable damage in return, making the entire exchange pointless. This assumption, of course, assumes that the Soviet/Russian mindset and mentality operates on a Western way of thinking when it comes to deterrence theory…   Pinstripedline has previously written on the Moscow Criterion and more details can be found at the link. However, the basic assumption of the Criterion was that in a best ‘worst case scenario’ the Polaris force was assumed to be able to get at least 17 nuclear warheads through Moscow’s defences and initiate a nuclear detonation.

The wider Cold War targets for the British nuclear force are less well known – there is some documentation available  that suggests during the 50s and 60s the RAF and USAF had an integrated role to play in the SIOP, having identified that they were both planning on bombing the same target. This led to much closer integration of British and US war plans throughout the 1960s as the V Force formed an integral part of SAC’s plan, ensuring that the V bombers and Canberra force would essentially blast a corridor into Russia ahead of the arriving SAC bomber forces, enabling them to destroy the main Soviet targets. There are some public suggestions that into the 1980s the ‘tactical’ nuclear role for RAF forces involved targeting of cities and installations in Eastern Europe and western Soviet Union to take these sites out in a similar way. It’s not publicly known whether as the UK adopted an SSBN force in the late 1960s if joint targeting continued for NATO war plans though or if planning diverged.

The Moscow Criterion...

The reason this matters is because it gets to the heart of how UK planners saw the role of the nuclear deterrent. It was to sit within NATO, to be operated as part of wider NATO efforts and ensure that NATO remained an international nuclear alliance, and that the decision to authorise nuclear release would be made primarily through NATO and not on a solely national basis. Briefing papers from the Cold War talk of the importance of ‘consultation’ by NATO members ahead of approving any request for release from military commanders (most likely SACEUR), and ensuring that the chain of command was followed. This was sometimes a cause for concern – in 1962 for instance a minor diplomatic crisis occurred between the UK and the US when the Minister of Defence:

“Wrote to SACEUR and SACLANT seeking assurances that they would not give orders to British commanders to use nuclear weapons until they had satisfied themselves that HMG agreed. The intention was to ensure that British commanders were not put in the invidious position of having to question orders from their NATO superiors while at the same time safeguarding the principle that British forces should not launch nuclear weapons without the specific authority of HMG. No replies were ever received to these letters”.

This then led to a lengthy series of top-level engagement between the UK and US governments to ensure that these very real questions of nuclear release were resolved before they became an issue in wartime.

In the 1960s, the role of the British Prime Minister was, as it is now, to be the final decision maker on whether to unleash the nuclear force. British thinking around nuclear release was based on several core assumptions. Firstly, that the Prime Minister would stay in No10/Cabinet Office until after release had been ordered, secondly that they would consult with the President of the United States prior to any release decision being taken, and that thirdly there needed to be sufficient resilience in the system to ensure that there was not a ‘single point of failure’ in the chain.

These assumptions around emergency plans were perhaps surprisingly not made automatically, and required one of the finest Cabinet Secretaries ever to hold the role (Sir Norman Brook) to set out a series of questions in a 1961 note to Admiral Mountbatten that asked:

“it would be helpful if we could work on agreed assumptions on such questions as “where would the Prime Minister be, can we assume the Government would remain in Whitehall until a nuclear attack had been launched on this country, what method of work would the government adopt”.

These questions led to a deep review of arrangements for how to command British nuclear forces during an emergency and ensure that the authorisation for retaliation procedures were tested, understood and robust enough to survive any reasonable scenario.

The assumptions reached were that a ‘bolt from the blue’ attack was highly unlikely, that the PM would remain in Whitehall until the end (“the Prime Minister, along with some of his principal colleagues and main advisors would remain in Whitehall until  a warning of nuclear attack on this country has been received and nuclear retaliation had been authorised, but that planning for the Prime Ministers survival of the attack should be confined to the arrangements already made for his speedy removal from London in an emergency”(OP VISITATION).

The challenges of nuclear release at this time were complex, emails did not exist and there were only finite phone lines or other signalling systems available. It was difficult to place transatlantic phone calls and communication satellites were in their infancy. Additionally, the relatively small Soviet nuclear force meant that any incoming nuclear attack would probably be identified some time in advance, probably delivered by air or slower moving ballistic missiles, and launch sites (as well as preparations to launch) would have been spotted in advance.

The 'Firing Chain' 1960s style

What this meant was that British planning for ordering “nuclear retaliation” (as the files describe it) was built on the idea that the Prime Minister would be in No10 during the crisis. During the modernisation of No10 during the early 1960s several sensitive secure speech circuits were installed that enabled him to speak by phone directly with the President, while the Cabinet Room and other areas had plugs installed to allow televisions (with long leads!) to be wheeled into a room to show information from other Whitehall crisis rooms. Of course, Treasury parsimony could be felt even in these most important of matters, as one file on nuclear retaliation procedures notes:

“The Foreign office requirement could be met with a ‘black and white’ system… The MOD requirement was for colour television. The Air Ministry stated, when they had considered a colour television system two years ago, they had rejected it on grounds of the great cost and the numbers of high-grade technicians compared with the cheaper and simpler ‘black and white’ system”.

The 1960s files make clear that the thinking was that the PM and War Cabinet would stay in London and receive information from MOD as the war developed, rather than leave the Capital. But plans still needed to be developed for enabling cover at inconvenient times when the PM was away from their office. This led, for example to consideration being given to developing a ‘mobile command post’ vehicle ‘such as the President has, to provide instantaneous communications for him at any time and wherever he might be”. Such a move was not approved, although other practical steps were – for example, as one of the very ‘in extremis’ moves was to ensure that the PM’s driver had sufficient coinage to dial into the AA network of roadside assistance telephones.

This ‘AA’ account is a good example of a sensible precaution becoming the stuff of myth. In the popular account it has been discredited as being a silly idea – but in fact it makes a great deal of sense. The credibility of deterrence relies on the enemy being certain that in the event of their launching an attack, a response is guaranteed. To ensure deterrence works, you need to consider every possible scenario and ensure plans are in place to cover them. In this case, the AA scenario was highly outlandish, but seems to have provided the contingency that in the event of a ‘bolt from the blue’ strike when the PM was not in No10, and there were no indications of crisis, that he could still be contacted if the least likely but worst case scenario (surprise nuclear attack) began. The moment that transition to war began, the PM and his closest advisors would probably not have left London. It was a sensible measure, unfairly ridiculed by those who don’t understand why it was done.

Retaliation and Deputies

The concept of continuity of control was taken a step further with the appointment nuclear deputies. This concept seems to stem from a review undertaken around 1961, probably post Berlin crisis when a major wider review of transition to war planning in HMG began. A working group was appointed to look at how the Government would sustain its nuclear retaliation procedures in times of crisis. Its conclusions were that Government (save select parties nominated for post-strike roles) would remain in London and that there would be a need to appoint at least two ‘nuclear deputies’ to assume authority for nuclear release should the PM be temporarily out of contact. The group also assessed that during the 1960s any attack on the UK would be by missile and air attack, with a few minutes warning likely of missiles and around an hour for bomber attack.

The concept of ‘nuclear deputies’ was intended to cover those periods when the PM was not available. For example, if the PM was travelling abroad, or was not in easy reach of military communications, they would be authorised to represent the PM on his behalf. Its easy to forget in an era of fast travel and instant communications how different the world of the 196s0 was. Travel was slow, there were few jet airliners in service, and it could take many days to reach far flung destinations. If the PM were in, for example, Australia or Africa, then it could be a week before he could get home, and communications links were not reliable enough for him to engage in secure conversations with the President.  The role of the nuclear deputy makes a lot of sense, ensuring that when the PM was away, there was always a minister within easy reach of the nuclear release machinery so they could be consulted if an attack seemed imminent.  There were two deputies appointed, on the assumption that in peacetime one could be in London, but if the international climate worsened, another could be at Bomber Command HQ, at RAF High Wycombe, and able to authorise release of the ‘V Force’ in a crisis.

Had the release of the V Force been approved, then the entire force would have scrambled – the RAF estimated that it would have needed 90 seconds to get airborne and 3 minutes to be clear of the airfields before a nuclear weapon detonated over them. In reality given the likely warning times, they would have probably had longer to get airborne. Once in the air the force would not have proceeded to launch a nuclear strike mission without further approval – which is where the nuclear deputy’s function was so important, because were London destroyed or out of contact, the deputy at High Wycombe could have authorised the mission to proceed instead. In absolute extremis, the RAF had decided to ensure that if the PM or a nuclear deputy was not available then:

“Ministers have approved arrangements to cover the eventuality that a nuclear attack having been received in this country before authority has been given to our nuclear forces to retaliate. In the last resort under this procedure, the Commander in Chief Bomber Command, is empowered to order, under his own responsibility, nuclear retaliation by all means at his disposal.”

Again, we see that these grim considerations were done to send a message (even if not publicly stated) that ‘the bomber will always get through’ and that a Soviet decapitation strike would fail. The command-and-control arrangements in place were robust enough that in all reasonable scenarios, sufficient warning and communications agreements existed to ensure that the UK could respond to a nuclear strike.

Bomber Command launch orders

What is notable during the 1960s though is the lack of understanding about how the US arrangements would work for release of weapons from their forces based in the UK. At this time there were a large number of SAC aircraft based in the UK, along with ‘dual key’ Thor IRBMs as well as other units. One line featured in the nuclear retaliation files is:

“we have no official information from the Americans about their THOR authorisation procedures. We know however that the orders would come from Strategic Air Command to Headquarters 7^th Air Division and that they would then go direct to the custodians on the various THOR sites”.

Another section noted that:  “full details of the United States procedure for authorising retaliation by their nuclear forces based in the United Kingdom are not known. The strategic forces in 7^th Air Division would receive their orders from Strategic Air Command but we have no details”. In other words, the UK at the time did not know how the US would authorise the launch of nuclear weapons based on its soil, some of which it had a dual key responsibility for. This highlights the importance of consultations between the Prime Minister and the President to agree the nuclear release before it was too late.

During the early 1960s the UK and US were the only nuclear powers in NATO and it was taken as a given in UK central planning that there would be consultation between the President and the PM before a nuclear attack was authorised. In part this was due to the integrated nature of the SIOP plans, the joint use of facilities and bases and also because if one nation went nuclear, the other could expect a nuclear response too. It is notable though that the decision to go nuclear would be taken not by NATO as a whole, as may be expected in a nuclear alliance, but by the PM and President alone. This raises interesting questions around whether either man would have risked a nuclear war in the 1960s to prevent Europe from falling under Soviet control or not.

Transatlantic Links for PM/POTUS

From a UK perspective the assumption was that the crisis would allow sufficient time for discussions around retaliation to occur ahead of the decision being taken. There was a recognition that the missile age removed the luxury of significant warning times of air attack and that difficult decisions would need to be taken quickly. According to one document, shown in the images below, the discussion around release would need to focus on decisions on the Polaris force, the Thor force, joint air assets and the agreement to order “R Hour” (the moment when SACEUR was authorised to release nuclear weapons). The view was that in the event of release being authorised, it would be a political decision taken to approve the weapons use, with the orders to employ them being given by SACEUR and executed by NATO units.

By the mid 1960s the UK plan was well crafted, and finely honed. Investment in command and control and provision of clear guidance meant that effectively there were two sets of nuclear retaliation procedures – those to be conducted under routine (if there is such a scenario imaginable) and those where alternative plans were required (e.g. the nuclear deputy or CINC Bomber Command). These were tested and regularly reviewed and seemed to work well. The arrival of the Royal Navy SSBN force in the late 1960s to  replace the ‘V Force’ though was a challenge that required significant rethinking of well-honed plans.

In the old system the V Force was a powerful tool because it could be launched, held at readiness and recovered without crossing a ‘go line’ without a signal. It could, if the situation demanded it, be recalled without the release of a nuclear weapon. By contrast the advantage of the SSBN fleet was that it would survive a first strike, as it was not vulnerable to attacks on airfields or infrastructure. But how do you plan for the release of a nuclear weapon when there is no equivalent to CINC Bomber Command able to authorise as his final act the launching of the V Force? The first hint of this problem was noted in a 1962 note by CDS Principal Staff Officer, which, among other things, stated:  “I for one am not sure how it is proposed to control the nuclear deterrent possessed by the Royal Navy” – clearly controlling the SSBN force would require a very different solution to that previously delivered.

The evolution of British nuclear release in the 1970s and 1980s occurred amidst the backdrop of massive changes to the civil defence planning for nuclear attack. Until 1968 plans existed to use the reserves, civil defence corps and other volunteers to provide widespread assistance after a nuclear attack had occurred. Following swingeing cuts to expenditure though, this was scrapped, along with the wartime use of the main relocation facility at Corsham, known variously as TURNSTILE, STOCKWELL and BURLINGTON. Instead, British planning focused on dividing the nation up into a series of regions, overseen by ‘Regional Commissioners’ (usually a mid-level Minister) and also setting up a series of groups known (initially at least) as PYTHON groups.  The latter group was to have comprised individual ministers – as a later 1980s briefing to the PM made clear:

“Plans exist which would enable Ministers to decide, if they so wished, on the dispersal of (REDACTED) groups (known as PEBBLE groups) of Ministers and officials during a period of tension or conventional war before a strategic nuclear attack. Each PEBBLE group would be an embryo central government, headed by a senior Minister.

If London were destroyed, the surviving senior Minister would take over the surviving central government and arrangements have been made for him to exercise control of the Polaris force at sea if neither you, nor one of the nuclear deputies survived…

I will submit in due course a revised list of contingent Ministerial appointments to the PEBBLE groups.  Individuals are not informed of their nomination in peacetime.”

The concept was at its heart surprisingly simple. In the event of war occurring the central government would either stay in London, primarily to authorise nuclear release, or send people out into the countryside as far from likely targets as possible to ensure that someone, somewhere would have the ability to exercise command and control over the SSBN force, even after nuclear attack.

This meant that by the 1980s UK nuclear release procedures were built on the principle that in the event of war, NATO commanders would request nuclear release, the member states would consult on the decision and then if approved would be passed to the UK and US for approval and execution (noting that these were the only sovereign nuclear powers in the alliance). At this stage the PM and President would consult and then agree on whether to authorise release or not – at which point SACLANT and SACEUR would be able to authorise release as they saw fit.  For the UK it was intended that:

“In normal circumstances control of the nuclear release would be exercised by you (the PM) from the Cabinet Office Briefing Room which is equipped with special facilities for this purpose…

In the single defined circumstance where nuclear weapons have actually burst in this country and political authority to release RAF aircraft for retaliation cannot be obtained along established channels, the Air Officer Commanding in Chief RAF Strike Command has standing delegated authority to order nuclear retaliation on his own responsibility. The reason for this exception is the survival of the tactical bomber force can only be achieved by ordering it into the air after which its ability to retaliate is limited in time by its relatively short endurance. The invulnerability of Polaris submarines makes it unnecessary to delegate equivalent authority to the Commander in Chief Fleet”.

Bomber Command ends the world by accident...

To ensure that release could occur under any reasonable circumstances the UK continued to see a need for nuclear deputies to provide the certainty of control even when the PM of the day was indisposed. To that end:

“the intention is that after formal appointment by the Prime Minister during a period of rising tension, the First Deputy would take post in Whitehall and be ready to cover any unavoidable absence by the Prime Minister. The Second Deputy would move on the Prime Ministers instructions to the headquarters of Commander in Chief Fleet at Northwood and assume authority were contact with the Prime Minister and First Deputy were lost”.

What this meant in practise is that in all imaginable circumstances of the Cold War, there were discrete arrangements in place to ensure that in the worst-case scenario, someone, somewhere, would still exercise command and control over the Polaris force. But what about if it all went completely wrong?  One of the challenges of deterrence is that you have to ensure that no matter how unlikely the circumstances, or random the event, that the deterrent will be sustained and credible. A potential aggressor has to know that there is nothing they can do to prevent a retaliatory strike, and that even a decapitation strike would result in nuclear response.

In the UK the challenge was that, unlike the US, warning times of a first strike would be short, that the command chain was relatively collocated (in the event of a nuclear attack on London, Northwood would almost certainly be struck too, sitting just a few miles from the centre of London). If a genuinely surprise attack occurred in peacetime, then there is no chance of a ‘PEBBLE’ group being formed or having the right comms in place (not just in the group, but also supported by the TA soldiers of the Royal Signals, many of whose wartime role was to support the P Groups assuming control of Government). This would mean that the SSBN would have no means of getting a nuclear firing chain message from the Government.

This is the so-called ‘Bolt From The Blue’ scenario and is one which makes good cold war fiction but in reality would have been impossible to deliver. Even as early as the 1960s, the Joint Intelligence Committee assessments, endorsed by MOD were that ‘a bolt from the blue is unlikely… the major risk of a global war arises from the possibility of a miscalculation in a period of international tension”.

For an attack of this nature to succeed in the SSBN era, it would require the Soviets to covertly mobilise for war, sending nuclear armed forces to their war stations and launching a strike of sufficient power to destroy all major NATO capitals, military HQ and command facilities, without leaving any possible survivors, and doing so without any possibility of detection. Given the scale of intelligence collection focussed on the USSR, and the well understood ‘indicators and warnings’ of mobilisation, preparation for war and a nuclear strike, it would require the greatest covert military operation in history to successfully deliver, and for what end? Destruction of NATO would invite certain retaliation from surviving forces, and in turn bring about the destruction of the Russian state. It is impossible to see any benefits to Russia of starting a war that it could not possibly win.

Grim nuclear humour

Despite this, the UK felt it important to ensure one final link in the chain that if all else failed, could ensure that a Prime Ministers wishes were carried out. To that end, each Royal Navy SSBN carries a safe onboard containing sealed envelopes. These are only to be opened when certain criteria are met. The first of which are instructions on the circumstances on which the second envelope, containing the Prime Ministers note, is to be opened.  The second note contains their wishes from beyond the grave, and sets out what the PM would want done in the event of a complete wipe out of all UK, US and NATO command and control and wider government, and the complete loss of all national C2 of the nuclear forces. The process was described in detail in a 1980s file, declassified some years ago:

“There remains the question of “last resort” , namely the procedures to be applied if this country were to be attacked in circumstances where the normal NATO command arrangements were ineffective for whatever reason and all organised government was destroyed, for example by a  ‘bolt from the blue’ nuclear attack from which neither the nuclear deputies, nor the PEBBLE groups survived.

This is not a situation easily provided for, but the argument is that if we do not provide for it – and should the Russians discover the fact – we do not have a deterrent which is credible in all circumstances. Present instructions to our Polaris submarine commanders are that if there have been indications that there has been a nuclear attack on the United Kingdom, or if all Polaris and other naval broadcasts have been silent for four hours, then a sealed envelope held by each submarine is to be opened. This envelope contains further instructions from the Commander-in-Chief, Fleet, which lays down the circumstances under which another sealed envelope containing instructions from the Prime Minister is to be opened. Mr’s Thatcher’s instructions cease to be operative, and I should like to discuss this matter with you, with a view to obtaining your decision on what the last resort orders should be”.

This chilling statement, prepared as a contingency paper for a previous incoming new government and Prime Minister (and released to the National Archives over a decade ago), sets out the difficult conversations a newly arrived Prime Minister would have to have early in their time in office. It is hard to think of a more challenging conversation to have.

This is why the press are reporting about the fact that Sir Keir Starmer will be writing these letters at some point in the very near future. But in doing so, they rather miss the point. If we reach the stage when the British Prime Ministers ‘letter of last resort’ is opened, then there will have been events of such magnitude and failure that, were any historians to survive the apocalypse, they would describe such events as the greatest intelligence failure in human history.

In the modern world the letters serve to remind us that in the UK, the nuclear deterrence mission is a genuine ‘cannot fail’ enterprise. For over 50 years thousands of service personnel and civil servants, both at sea in submarines, deployed more widely on surface ships, aircraft and RFAs, or working ashore, have laboured hard under all manner of circumstances to ensure that ‘the bomber will always get through’. The letters serve as a reminder that every contingency is accounted for and that even in the worst-case scenario, deterrence will not fail.

The letters of last resort exist not because they are needed, and the whole point of the system is to put so many different routes in place to ensure that command can be exercised over the nuclear force that the single most unlikely occurrence is practically impossible to happen. The letters instead serve as a potent reminder to any adversary that there is no way they could avoid retaliation. They also serve to remind the incumbent of the office of Prime Minister that there is a grave and deeply serious responsibility which falls uniquely upon their shoulders.