Nuclear strike
Long Reads

Lima Charlie: Who Really Controls The UK's Nuclear Deterrent?

'Despite false rumours and confident assertions of blokes down the pub, the US does not have the ability to control UK nuclear deterrent.'

Nuclear strike

For the last 50 years, the Royal Navy has maintained a succession of nuclear submarines on constant patrol to provide the ultimate guarantee of UK national security. This mission, known as OP RELENTLESS involves keeping a nuclear-armed Ballistic Missile Submarine (SSBN) constantly at sea on patrol and able to launch a nuclear strike against any potential aggressor if required. 

Since becoming a nuclear weapons state in 1952 the UK has employed a variety of means of operating and delivering nuclear weapons in both ‘tactical’ and ‘strategic’ roles on land, sea and air.

These methods have sometimes involved purely UK ‘national’ weapons, and at other times the so-called ‘dual key’ weapons that were jointly operated with the US.

Today the UK maintains an independent strategic nuclear deterrent which consists of British designed and built nuclear warheads mounted on a Trident missile and deployed onboard a British designed and built ‘VANGUARD’ class ballistic missile submarine. 

Some commentators though believe that the UK does not have a genuinely independent deterrent and that somehow the US Government is able to control it and block its use. This is a myth, but one that is strongly believed by many people. The purpose of this article is to examine in more detail how this myth came about, and why it is so untrue.

The original UK nuclear deterrent was delivered through the Royal Air Force, which operated the ‘V Force’ consisting of Valiant, Vulcan and Victor bombers. This force was intended to launch a nuclear strike on the Soviet Union, having the capabilities to drop free-fall nuclear weapons on cities and other targets.  

In the 1950s through the UK had a relatively small stockpile of nuclear weapons, for example just 14 nuclear weapons were available in 1956, despite having a large number of aircraft capable of delivering a nuclear strike mission. To make the best use of the capability while the UK stockpiles were worked up, the RAF worked closely with the US Strategic Air Command (SAC) to coordinate mission planning and ensure that the UK assets fitted into wider US plans. This was in part because, in the event of an all-out nuclear war, the RAF could get aircraft into Russia hours ahead of the US Air Force, playing a vital role in knocking out targets that could threaten the main bomber offensive.

To resolve this, the UK made arrangements for a number of US nuclear weapons to be assigned to the V Force in wartime, with the US government supplying over 70 nuclear bombs for use. Under the terms of the agreement, the US stipulated that the UK could not service or have control of the weapons, which remained US property and were maintained and guarded by US personnel  – effectively ensuring that the US was able to operate a veto on UK nuclear operations. This arrangement came to an end in 1962 when sufficient UK nuclear weapons were available. 

At this time then it was reasonable to assume that the US would have been able to exercise some control over the UK nuclear deterrent mission – although in reality the close coordination between the two nations would have meant it inconceivable that the UK would launch an attack without the US also participating too.

By the late 1950s, with the improvement of Soviet air defences, the ability of RAF bombers to successfully fulfil their mission was rapidly declining.

Instead, plans were to re-equip the V Force with a short-range stand-off capability known as the ‘Blue Steel’ missile. This would allow the RAF to fire missiles into Soviet territory without having to reach the target itself, thus increasing survival chances.

It was realised that in the medium term there would need to be significant changes to ensure that a nuclear weapon could be delivered effectively without being shot down en-route by Soviet forces. The best way was a missile with a much longer range, initially identified as being the British designed Blue Streak missile. This was cancelled in part when the cost of building the underground silos to host it around the UK was identified as being disproportionately expensive. Instead, it was agreed that the UK would co-operate with the US on purchasing the ‘Skybolt’ missile, a long-range (over 600 miles) missile that could deliver a nuclear warhead. 

The Skybolt was cancelled by the US in 1962 leaving the UK potentially without a credible nuclear deterrent capability from the late 1960s onwards. 

The combination of an ageing and less effective RAF bomber force that would struggle to break through enemy air defences, and the reality that the UK could not really afford or find suitable locations for a land-based missile system meant that drastic changes were needed to ensure the UK could remain a credible nuclear power.

To resolve this crisis, in 1962 the UK signed the Nassau Agreement with the US which attempted to find a way through these challenges. The agreement saw the US agree to provide the UK with access to the Polaris missile, an Intercontinental Ballistic Missile (ICBM) that could be launched from a submarine. These missiles would carry British designed and built nuclear warheads, and be committed to NATO as part of wider multi-later deterrence efforts. This move would take the deterrent force away from the RAF and instead place it firmly in the hands of the Royal Navy.

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The Nassau Agreement is one of the most significant parts of British nuclear history, for it represents the point where the UK took a considered decision that to remain a credible nuclear power, it would either need to invest a very substantial amount of cash in developing its own systems, money that was in short supply and which would have come at the cost of conventional defence, or it could work in alliance with others. The decision by the US to sell Polaris to the UK meant huge sums of money were saved on research and development (over $800m in 1962 prices) and ensured that as the UK withdrew from Empire, it was still able to maintain an effective nuclear capability. 

The end result of the Nassau Agreement was the construction of four Ballistic Missile Submarines (known as SSBNs), named the RESOLUTION class that entered service from the late 1960s onwards. At roughly 8000 tonnes displacement, they were the largest submarines ever operated by the Royal Navy to that point, they were built in an average of just four years (in significant contrast to the challenges experienced by the current ASTUTE class that are currently closer to 10 years).

Each vessel was armed with 16 Polaris missiles, capable of delivering nuclear warheads roughly 2500 miles and destroying large cities or other substantial targets.

Crucially, although the missile was US derived, the UK retained ownership of the warhead and was responsible for ‘mating’ the warhead to the missile. The result was the Polaris was able to deliver a British designed nuclear weapon using a US missile, but without the US playing any part in the operational decision to fire the missile. The UK was thus able to maintain an independent strategic nuclear deterrent.

Polaris missile launch from HMS Revenge, in 1983
Polaris missile launch from HMS Revenge in 1983

The first SSBN patrol occurred in 1968, with the Royal Navy then moving to a continuous series of patrols in May 1969. Since this point, for 50 years now, there has always been a Royal Navy SSBN on patrol capable of conducting a nuclear strike if required. 

Polaris was operational from the late 1960s until the mid-1990s when the submarines were retired from service. Their replacement was the VANGUARD class of SSBN, which deployed the Trident missile system, a substantially larger weapon with much longer range (more than 7500 miles) and ability to carry significantly more warheads (Polaris submarines could carry between 16 and 32 warheads, while Trident submarines could, as originally designed have carried up to 14 warheads per missile). 

The VANGUARD class entered service in the mid-1990s just as the Cold War came to an end, but have continued to maintain the at sea deterrent mission. As a result of changes to the international system, and as part of the wider reduction in nuclear tensions, these submarines now routinely deploy with fewer than 16 missiles (usually around 8) and only around 40 nuclear warheads embarked at any one time (from a total stockpile of around 220 warheads).

Although the UK is clear that the system is an utterly independent nuclear deterrent that can be only fired on the express decision of the Prime Minister, there are plenty of people out there who believe that the system is somehow under US control, and that it can be prevented from firing without their permission.

One reason why some commentators feel that the US can exercise control over the UK nuclear deterrent is due to the slightly unusual purchase terms for Trident. Unlike Polaris, where the UK purchased the missiles outright and then maintained them in Coulport, the decision was taken to lease access to Trident missiles instead.

In practical terms, this means that the UK does not physically own a specific missile (as it did for Polaris), but rather has purchased the right to draw on 58 Trident missiles from a joint pool. Unlike during the Polaris years, when a VANGUARD class SSBN emerges from refit, rather than having the missiles loaded locally in Coulport, it instead travels to Kings Bay in the US state of Georgia, home of the US Atlantic Fleet SSBN force. 

Here the missiles are selected at random from the pool and loaded onto the submarine, which then returns to the UK for the nuclear warheads to be ‘mated’ onto the missile itself at Coulport.

The advantage for the UK is that it is able to piggy back off the much larger US programme and benefit from economies of scale.

During the later Polaris years, especially after it had left service in the US, the UK Government found itself responsible for paying for the development and maintenance costs of the missile stockpiles, which became extremely expensive to manage. 

By contrast, pooled asset ownership with the US means that the UK can pay into a much larger organisation and benefit from economies of scale from the US Navy funding upgrades and maintenance work. Because the missiles are fully interchangeable, it is possible for a missile to do patrols on both British and US SSBNs at different times. 

Some commentators believe that this lease arrangement gives the US control over the missile in some way, which would prevent them from allowing the UK to launch a nuclear strike. Such a claim is not true, the missiles are selected at random and there is no material difference between a UK or US missile. The US is unable to exercise any control over UK Trident missiles remotely because it does not know ahead of time which missiles will be selected for use in a UK submarine. 

The UK also benefits from this joint pool in other ways – for example, the ability to use US ranges to conduct the regular ‘DASO’ (demonstration test) firing to ensure that the system works properly. This occurs in the US and provides the UK access to instrumented test ranges and other essential support that would otherwise cost a lot of money to secure.

Trident nuclear submarine USS Louisiana (SSBN 743), 2005
Trident Nuclear Sub USS Louisiana

Once a Royal Navy SSBN has been equipped with its load of missiles and warheads, it will then sail on patrol for around three months, disappearing into the ocean and remaining totally radio silent. Under no circumstances is an SSBN to break silence and radio for assistance. Instead, the role of the submarine is to disappear, receiving orders from the UK and, if called upon, to fire their missiles. 

This is a uniquely demanding way of life, for the crew receive messages from home and news updates that the vessel is picking up, but they are unable to respond or acknowledge them.

Even the slightest hint of a transmission from an on patrol SSBN may indicate to a potential foe about their current position and the wider patrol area, which could in turn risk the security of the deterrent.

One of the myths about the nuclear deterrent is that somehow the US has the codes or the ability to interfere with the firing chain and prevent a submarine on patrol from launching its weapons. In reality in the event of a decision being taken to fire a Trident missile, a complex series of events needs to occur involving a purely UK national chain of command. 

The specifics of how this chain works is a closely guarded secret, but in broad terms it involves the Prime Minister approving the employment of nuclear weapons, and the order being transmitted to the submarine via a series of UK controlled communication channels, which in turn, if properly authenticated, would see the submarine launch as ordered.

The US system relies on a series of ‘Permissive Action Links’ (PALS) which are a form of cut out designed to ensure that a US nuclear weapon cannot be released with political authority. It is perhaps this system that critics believe would prevent the UK from firing a missile without US authority – perhaps confusing a US national system with one that is in place on each Trident missile. 

In reality, the PALS system is something that the UK government does not have in place, preferring instead to rely on alternative command and control systems for its nuclear arsenal. Therefore it would be utterly impossible for the US to ‘control the launch codes’ because the UK does not share this system.

Others have suggested that somehow the US could refuse the launch of the weapons physically, although how this would happen is unclear. There are no US naval personnel embarked on any UK SSBN (and vice versa) who could prevent such a launch from occurring. Outside of some very bad fiction (possibly involving a Navy SEAL masquerading as an exchange chef?) it would be impossible for the US to physically prevent a launch from onboard the submarine.

The other reason why the US could not physically prevent a UK launch is due to the unique arrangements covering the release of British nuclear weapons. During the Cold War it was accepted that a ‘bolt from the blue’ strike could decapitate the relevant UK authorities with the ability to order a launch before a retaliatory strike could be approved. While this was less of an issue during the time of the V Force, as it was likely that airfields hosting bombers would identify the attack and launch a response, it became much more of an issue with the introduction of the SSBN force, who may not be warned in time of the attack.

To prevent the circumstances arising where the UK was wiped out by a nuclear attack, all Prime Ministers were required to draft a ‘letter of last resort’ which were written on assuming office.

Distributed to each submarine, they provided direction for the Commanding Officer on what to do if the UK was wiped out by a nuclear attack, and they were unable to find any remaining government to report to.

In those circumstances the letter, stored inside a special safe, was to be opened and the Prime Ministers wishes from beyond the grave would be acted on. No one other than the Prime Ministers who wrote them knows what their contents were, because the letters are destroyed unread at the end of their time in No10. It has been speculated though that the letters may instruct the CO to fire on whichever nation was deemed responsible for the attack, or to put themselves under the command of an allied nation. 

This matters because it shows that the UK nuclear firing chain is sufficiently robust that, in the most absolute extremis, it is possible to launch a nuclear strike without external input. This is important because it helps dismiss the ideas that some have about the US controlling the launch codes or other similar ideas.

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One reason where these ideas may come is from a bit of confusion with arrangements for other nuclear weapon systems which were ‘dual key’. For example, during the Cold War the UK had arrangements to use US nuclear depth bombs to attack submarines, and also the Army used the ‘Lance Missile’ a US-provided battlefield tactical nuclear missile in service with the Royal Artillery. Additionally, the RAF used the ‘Thor’ missile – an intermediate range ballistic missile for a short period of time too, again provided by the US.

To help underpin NATO’s status as a nuclear alliance, these nuclear weapons worked by the US retaining custody of the nuclear warheads, and the host nation providing the launch capability. The weapon could theoretically only be employed if officers from both nations ‘turned their key’ (or other form of release mechanism) to enable the weapon to be fired. 

These arrangements persist to this day, with the US retaining a large number of B61 tactical nuclear weapons across Europe for use by NATO allies including Germany and the Netherlands. These weapons are owned by the US but intended to be delivered through national aircraft – such as the German Tornado force, although it is not clear if the B61 will be cleared on to Eurofighter Typhoons in due course. 

In these circumstances the US absolutely does have the ability to prevent a launch, but this control over a tactical nuclear weapon, intended for use on the battlefield is very different to their being able to control an independent UK nuclear launch.

The last area where people believe that the US could exert control over the UK nuclear deterrent is by the use of GPS for fixing positions on the targets. By turning GPS off in a crisis, they could apparently prevent the UK from firing. In reality, the Trident missile can use navigation techniques that rely on star sighting in the constellations, which is immune to any form of jamming. Such a move would, therefore, have absolutely no impact on the UK’s ability to launch a nuclear strike if it chose to do so. 

The only way that the US could, in theory, assert long term control to the UK would be if they were to cease providing access to the missile pools or refuse to sell certain items needed for refits and repairs – for instance providing new equipment for the missile compartment technology. Such a move would take many years to have a direct impact and it is difficult to see the circumstances arise where the US would willingly do this without there being a very substantial shift in international relations. 

In reality, the UK and US enjoy a uniquely close relationship on nuclear issues, which is mutually beneficial to both nations. Not only do their attack submarine forces operate exceptionally closely together (as seen in 2018 by the deployment of HMS TRENCHANT to the North Pole alongside two US Navy submarines), but there is also close co-operation in the development of future capability too.

The next generation of SSBNs are under construction in both the UK and the US, known as the DREADNOUGHT class in the UK and the COLUMBIA class in the US Navy. Although different designs built to reflect the individual philosophies of each navy, they also share one feature in common – the so-called ‘Common Missile Compartment’ or CMC. 

This will be the part of the vessel that houses and launches the missiles and is central to the deterrent mission of the submarine. The Royal Navy is sharing in the development costs of the CMC with the US Navy and will be the first nation to take it to sea, as HMS DREADNOUGHT is due to enter service ahead of her American cousins. 

The UK’s experience in operating this capability will be vital for the US Navy to learn from, and ensure that it works as intended.  It is a good sign of just how close the UK and US relationship is that the US Navy is content to let a foreign navy trial the missile compartment that will be central to the sustaining of the US nuclear deterrence posture for the next 40 years. 

There is wider co-operation too on a scientific level as both nations work closely together on warhead issues, with both the US and UK likely to produce independent designs over the next few years for the next generation of nuclear warhead. Although both nations maintain an independent approach to their warhead design, the fact that both are able to work closely together helps generate joint benefits in research and development. 

It is clear then that the UK is not reliant on the US for its nuclear capability, nor can the US ‘switch it off’ or otherwise control it. Instead the UK remains a highly valued partner able to independently operate a nuclear deterrent, but which has chosen to make sensible decisions about how to get the most cost effective outcome, by sharing missiles with another nation.

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By contrast, the French Government has chosen to sustain an independent nuclear capability, also built around both an SSBN force and some air-launched tactical nuclear missiles. This force is entirely designed and built in France, and the financial burden of this falls squarely on the French taxpayer. 

Historically the cost of the French nuclear force occupied a large chunk of their defence budget, reducing available funding for other defence capabilities. In due course, the French will need to find funds for an entirely new SSBN and ICBM without the benefit of international co-operation – a high cost to pay for a truly independent deterrent capability. 

The experience of the French serves as a timely reminder that the UK, without doubt, took the right decision to work closely with the US in nuclear matters. Unlike the French the UK has been able to afford to build and sustain a wider range of military capabilities that matter to the US – for instance, two new aircraft carriers, a large amphibious force and regenerate its air to air refuelling and strategic airlift forces too. 

Had the UK remained a purely national nuclear power, determined to mirror the French approach, then it is hard to see how the country could have afforded to operate a nuclear deterrent and a global military presence too throughout the Cold War and beyond. Something would have had to have been sacrificed to pay for sustaining the nuclear capability – would this loss of conventional military capability have been a price worth paying to keep the UK as a credible nuclear power? 

As the Royal Navy approaches 50 years of unbroken nuclear deterrence operations at sea, it is worth contemplating the huge sacrifices and efforts made by thousands of people to make it possible.

It has played a central part in deterring Soviet aggression during the Cold War, and today serves as a key consideration to nations like Russia, or rogue states like North Korea and Iran that they threaten the UK at their own risk. 

The support of the US Government and Navy has been invaluable in making this happen, but the UK deterrent has always been, and will always be, truly independent and not subject to the whims and control of another nation.

Despite many false rumours to the contrary, and confident assertions of blokes down the pub, the US does not have the ability to control the UK nuclear deterrent.

This article is the latest contribution in our Lima Charlie columnist section.

This is part of a series featuring unattributed contributions from experts and insiders providing opinion, insight and analysis on today’s Armed Forces, the wider politics of the military and observations on military life.

Under the pseudonym Lima Charlie, our contributors aim to explore the issues facing today’s military and their comment remains unattributed to allow our writers to present their analysis candidly and under one editorial voice.