A Disturbance in the Force: Debating Continuous at-Sea Deterrence (RUSI report, January 2014)

8/13/2019 A Disturbance in the Force: Debating Continuous at-Sea Deterrence (RUSI report, January 2014)

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About the PaperThis Occasional Paper is part of a series commissioned by the Nuclear Security Project(NSP) of the Nuclear Threat Ini a ve (NTI), which examines key factors that will shapethe UKs nuclear forces over the course of the next decade.

Other papers within this series include an analysis of the pressures shaping the futureof the UKs nuclear warheads; a discussion of the UKs approach to replacing its nuclearforces; and an analysis of the role of UKs co-opera ve nuclear rela onships in thisprocess.

Each paper presents these factors within their historical context, and examines boththe poli cal and technical issues that drive them. Their role in shaping the future ofthe UKs nuclear forces is then discussed with reference to archival sources, researchinterviews and technical studies.

The views expressed in this report are en rely the authors own and not those of theNSP or NTI. For more informa on, see www.nuclearsecurity.org

About the ProgrammeThe Nuclear Analysis Programme at RUSI carries out comprehensive research projects,

convenes expert discussions and holds public conferences on various contemporaryaspects of nuclear non-prolifera on, security and disarmament. The programmesprimary research areas are on na onal and interna onal nuclear policy and strategy,with par cular a en on paid to regional nuclear issues, UK nuclear policy, andmul lateral disarmament and non-prolifera on regimes.

About RUSIThe Royal United Services Ins tute is the UKs leading independent think tank oninterna onal defence and security. Its mission is to be an analy cal research-led global

forum for informing, in uencing and enhancing public debate on a safer and morestable world.

Since its founda on in 1831, RUSI has relied on its members to support its ac vi es.Annual membership subscrip ons and dona ons are a key source of funding for theIns tute; together with revenue from publica ons and conferences, RUSI has sustainedits poli cal independence for over 180 years.

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For more informa on, please visit: www.rusi.org


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A Disturbance in the Force

Hugh Chalmers

Occasional Paper, January 2014

www.rusi.org

Deba ng Con nuous At-Sea Deterrence


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The views expressed in this paper are the authors own, and do notnecessarily re ect those of RUSI or any other ins tu ons with which theauthor is associated.

Comments pertaining to this paper are invited and should be forwarded to:Hugh Chalmers, Research Analyst, Nuclear Analysis, Royal United ServicesIns tute, Whitehall, London, SW1A 2ET, United Kingdom, or via e-mail [email protected]

Published in 2014 by the Royal United Services Ins tute for Defence andSecurity Studies. Reproduc on without the express permission of RUSI isprohibited.

About RUSI Publica onsDirector of Publica ons: Adrian JohnsonPublica ons Manager: Ashlee GodwinEditorial Assistant: Cathy Haenlein

Paper or electronic copies of this and other reports are available bycontac ng publica [email protected].


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A Disturbance in the Force

The tradi onal theory of deterrence suggests that the most e ec ve wayof dissuading an enemy from hos le ac on is with the certainty that suchac on would be promptly followed by devasta ng retribu on. For the pastforty- ve years, the UK has provided this certainty by maintaining a nuclear-armed submarine on patrol at all mes, ready to re if required.

However, it is also accepted that in prac ce such certainty is not alwaysachievable. 1 The eet of Vanguard -class submarines that currently operatesthis tag-team patrol, known as con nuous at-sea deterrence (CASD), willeventually re re to be replaced by a successor. While current UK policy

states that a replacement eet will take up this baton and maintain CASD forthe foreseeable future, this will not be without cost.

The UK government has stated that maintaining CASD will require a eet ofat least four submarines, one of which will patrol while the remaining threeundertake training, undergo maintenance, or sit in reserve (see Figure 1).Current es mates suggest that such a eet would require up to 18 billionin capital investment, in addi on to running costs which may ul matelyincrease the total through-life cost to 80 billion. 2

Figure 1: Indica ve Con nuous Patrolling Cycle with Four Submarines.

Note: Periods are illustra ve only; a period may be longer or shorter than others.

Poin ng to concerns about these costs and limited public support for thelike-for-like replacement of the Trident system, the Liberal Democrat Party

secured a review of possible alterna ves when they entered governmentin 2010, which was conducted by the Cabinet O ce and released in July2013. To the chagrin of disarmament advocates, this review did not considerthe the UKs unilateral abdica on of its nuclear status. However, it didconsider abandoning CASD; a move that would allow the UK to shrink thesize of its future submarine eet and mi gate a por on of its cost, whilstsimultaneously making a gesture towards nuclear disarmament. 3

Abandoning this long-held patrol structure would place the UK in aunique posi on amongst all nuclear-weapon states, none of which havevoluntarily adopted a single, non-con nuous nuclear force. Furthermore,the civil servants and armed forces that develop and implement the UKs


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A Disturbance in the Force2

nuclear-weapons policy have spent their en re careers working within the

constructs of CASD. For them, a step away from CASD would be a step (bothbureaucra cally and philosophically) into the unknown.

The Trident Alterna ves Review (TAR) outlines three primary issues thatwould determine the desirability of non-con nuous patrolling postures. First,it ques ons whether back-to-back patrolling can be sustained long enoughwith a smaller eet of submarines to cover any emergent crisis. Second, itques ons whether the UK could ac vate an inac ve eet in me to dealwith any such crisis. Finally, it ques ons whether a poten al aggressor wouldlaunch an a ack against an inac ve eet without presen ng the UK with anopportunity to deploy and protect its forces.

There are two broad camps in the debate. On the one hand, it has beenargued that ini a ng patrols as a crisis emerged would be di cult, clumsy,and could alarm adversaries, inci ng a destabilising spiral of escala on. 4 Furthermore, some believe that introducing any period of inac vity will castuncertainty into the minds of adversaries as to the probability of retribu on,thereby signi cantly reducing the deterrence such a force might provide. 5 Onthe other hand, it has been argued that ini a ng patrols is not necessarily atripwire of catastrophic escala on, and that even a modest chance of a hugepenalty can have great deterrent force. 6

As always, the devil is in the detail. While on the surface the UK seems toface a simple binary choice, there are in fact a variety of patrolling op onsthat could bring it closer to or take it further away from CASD. 7 Furthermore,the non-con nuous op ons that have been discussed so far have only beenpublicly outlined in principle. There is li le informa on to suggest how thesepostures would be realised in prac ce.

This paper contributes to the debate over CASD by discussing how theprac cal applica on of non-con nuous patrolling can a ect the three mainissues outlined in the TAR. To do so, it presents the role CASD currently plays

in the UKs nuclear posture, and describes the alterna ves that have beenproposed so far. It then addresses the three issues described above in turn,by detailing how the risks of inac vity and vulnerability evolve in smallersubmarine eets, and discussing how the eets ac va on or deac va onmight a ect, and be a ected by, the broader interna onal context. In doingso, this paper argues that if the UK can develop procedures for ac va ng,sustaining, deac va ng and repairing a smaller eet of nuclear submarines,which are simultaneously exible and reliable, then many of the risks of non-con nuous patrolling postures could, in principle, be mi gated.

However, ques ons remain over how achievable this aim really is. Havingspent forty- ve years maintaining a con nuous patrol, the UK has very li le


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experience dynamically adjus ng its patrolling schedule in line with an

evolving threat environment. Furthermore, developing procedures to do sowould naturally have to draw from an understanding of when the UK mightwish to call upon its nuclear force: something the UK has so far only outlinedin the vaguest possible terms.

Comfort in Con nuityThe UK is not alone in its con nuous deployment of nuclear submarines.Of the four nuclear-armed states with opera onal submarine-basedforces, three (the UK, France and the US) are known to maintain at leastone submarine at sea at all mes. 8 While suspicions remain over its abilityto maintain con nuous patrols, Russia announced in 2012 that it would

also return to CASD. 9 This raises the ques on over the apparent appeal ofcon nuous submarine patrols.

Tim Hare, former head of UK nuclear policy within the Ministry of Defence(MoD), argues that if we are to pay such a large sum of money as an insurancepolicy against nuclear threats, then it is a given that such a capability shouldbe e ec ve. For a deterrent to be e ec ve, it must be credible. 10 The TARintroduces ve criteria by which it judges the credibility of the UKs nuclearforces: their readiness, reach, survivability, destruc ve potency and the UKsresolve to use them. Maintaining a con nuous nuclear patrol contributes tothree of these readiness, survivability and resolve.

To launch its missiles, the Vanguard -class submarine ejects them from itsmissile compartment with compressed air un l they reach a safe distancefrom the boat to ignite. While in principle this approach should allow asubmarine to safely launch a missile from under water or from the surface,in prac ce surface launches have not been explored for current or futuregenera ons of submarine. Once surfaced, both the UKs current and futuresubmarine forces will not be able to re their missiles.

Therefore, by maintaining a con nuous patrol, submerged submarines can

launch a nuclear a ack as quickly as the ring chain and the comple on ofany secondary tasks (such as running repairs or training exercises) will allow.Current UK policy restricts these factors such that a submerged submarinecan always launch an a ack within several days of an order being given. 11 In prac ce, if a patrolling submarine is not preoccupied, this delay could beshortened to a ma er of hours, and possibly less.

Furthermore, it is extremely challenging for an adversary to locate andsubsequently disable a nuclear submarine once it is deployed within the vastexpanses of the ocean. By maintaining a submarine on patrol at all mes,the UK can reassure its allies and convince its adversaries that its nuclear


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forces are invulnerable to a rst strike, and remove a possible incen ve for

pre-emp ve a acks.

In addi on to these opera ve factors, it has been argued that the broadere ort of maintaining con nuous patrols reinforces the impression thatthe UK is actually prepared to carry out its deterrent threats. For instance,the TAR states that by regularly expending the nancial and personnelresources required by CASD, the UK can demonstrate a strong and consistentcommitment to its nuclear forces, and that it has the resolve to use them ifnecessary. 12

While con nuous patrols make a contribu on to the readiness, survivability

and resolve of the UKs nuclear forces, they make li le contribu on to theirreach or destruc ve power. Aside from the issues associated with ring aTrident missile while surfaced, the opera ng tempo of UK submarines hasno e ect on the potency of the warheads it holds. Similarly, the opera ngtempo of the UKs future nuclear forces will have almost no e ect on theirrange. The next genera on of nuclear submarine will be armed with up toforty warheads on eight missiles. 13 On average, therefore, less than half of themissiles capacity will be used, which increases the range of the missiles upto approximately 11,000 km. This makes far- ung deployments unnecessaryby giving the UKs missiles in e ect a global range. 14

Maintaining an unbroken nuclear capability does not create a credibledeterrent by itself. Je rey Lewis observes that the Chinese leadership believesthat nuclear deterrence is rela vely insensi ve to changes in the size,con gura on, and readiness of nuclear forces. 15 Re ec ng this belief, Chinesenuclear warheads are currently held separately from their launching systemson a day-to-day basis, and the two are only mated when intelligence suggestsa heightened threat level. 16 As such, China voluntarily places its nuclear forcesbeyond short-no ce use, con dent in the knowledge that it can recons tutethem when necessary. One can similarly look to the nuclear arsenals of Indiaand Pakistan; while neither is housed on invulnerable pla orms held at a

con nuous level of readiness, both are o en seen to have played a role in thedeterrence of major con ict. 17 While these postures may change in the future,this does not imply they were unsuccessful in the past.

Thus while con nuous patrolling probably enhances the credibility of theUKs nuclear forces, it does not embody it. It is not immediately apparent ifRussia, China or, indeed, any other state would feel any less threatened bythe UKs nuclear forces were they occasionally unavailable. While many ofthe UKs allies would be taken aback by such a change in its nuclear posture,with proper presenta on and integra on into NATOs nuclear structures itcould s ll make a useful and reassuring contribu on to the Alliances shared


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nuclear force. Abandoning CASD is therefore not a priori incompa ble with

a credible nuclear threat.

A Ladder of Nuclear Capability and ReadinessAccording to the TAR, there are a number of non-con nuous postures whichcould deliver at short no ce a nuclear strike against a range of targets atan appropriate scale and with very high con dence while submarines aredeployed in a crisis. 18 However, these postures vary in both the proposedfrequency of deployment and their readiness to deploy in response tochanges in the interna onal environment.

At lower readiness, the preserved deterrence posture presented in the

TAR and the con ngency posture proposed elsewhere by the LiberalDemocrat Party would have no nuclear pla orms deployed on a day-to-daybasis, and would only have the ability to recons tute a force over a limitedperiod of me (in the case of preserved deterrence, a ma er of years). 19

At medium levels of readiness, the sustained or responsive posturespresented in the TAR would have nuclear-armed submarines patrolling ona day-to-day basis, interrupted by voluntary periods of inac vity of varyinglength (the former permi ng fewer and shorter interrup ons than thela er). At higher levels of readiness, the focused posture would maintainback-to-back patrols, interrupted only for periods of technical or personnelrecupera on.

The TAR suggests that the UK could move from one posture to anotherto match the interna onal threat environment, raising or lowering thereadiness and vulnerability of its nuclear forces. For instance, the UK couldadopt a preserved deterrence while there were no nuclear threats on thehorizon, but switch to a higher-readiness posture as such threats emerged;an approach described by Danny Alexander, chief secretary to the Treasuryand the minister responsible for overseeing the TAR, as a ladder of nuclearcapability and readiness. 20 In this sense, the UK could alter the readinessof its submarine forces so that they are only as credible as they need to be

given the interna onal situa on.

Re ec ng the view expounded in the 2010 Na onal Security Strategy (NSS)and Strategic Defence and Security Review (SDSR) that the UK currentlyfaces no threats to its integrity or independence, the Liberal Democratshave argued that the UK can take a few steps down this ladder of capabilityand end nuclear-armed patrols on a day-to-day basis. 21 Their con ngencyposture, outlined separately from the Cabinet O ce-led TAR, would disarmthe UKs nuclear submarines and keep them in port, whilst exercisingsubmarine capability regularly to maintain relevant skills, including weaponshandling and nuclear command and control. If the survival of the state isconceivably at risk, submarines would then be surged to more constant


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armed patrols for a limited period of me e ec vely climbing back up the

ladder of capability to a posture of medium or high readiness.22

Table 1: Non-Con nuous Patrolling Postures.

High Readiness Focused(TAR)

Unbroken patrols sustained for a setperiod of me; patrols cancelled only forperiods of recupera on

Medium Readiness Sustained(TAR)

Patrols are sustained by one on-dutyboat, and are only interrupted byoccasional and brief returns to port

Responsive(TAR)

Patrols are conducted sporadically and inan irregular fashion

Low Readiness Con ngency(LiberalDemocrat)

Submarines are typically held unarmedin port, ready to deploy within a speci cmeframe to more constant patrols

Preserved(TAR)

Submarines are typically held in port,ready to deploy in a ma er of years. Onesubmarine held at medium readiness todeploy

The UK considered a similar de-alerted posture in 1998, but rejected it onthe grounds that ending con nuous deterrent patrols would create newrisks of crisis escala on if it proved necessary to sail a Trident submarine ina period of rising tension or crisis. The further step of removing warheadsfrom missiles would also add a new vulnerability to our deterrent posture. 23 Cri cs of non-con nuous postures argue that the same fears that dissuadedthe UK from adop ng a non-con nuous posture in 1998 are s ll very muchrelevant today.

As will be discussed below, Members of Parliament have voiced concernsthat by introducing the presence (or prospect) of inac vity and vulnerability,a non-con nuous posture is simply not credible and very dangerous. 24 Furthermore, the government might also feel pressured into undesirableac ons by the fear of sustained patrols being interrupted at unfortunatemoments. Finally, it has been argued that while submarines are inac ve,the government would have to confront a terrible choice as to when tomake the tremendously escalatory move [to ac vate them] that would turna mere dispute into an acute crisis. 25


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Sustaining Patrols

To guarantee unbroken patrols, the current eet requires four submarinesto juggle the compe ng tasks of patrol, repair, training and si ng in reserve.If one submarine were to be removed from this eet, the remaining threewould have to take up the slack and sacri ce a por on of their me to carryout the tasks of the lost submarine (see Figure 2).

Figure 2: Indica ve Con nuous Patrolling Cycle with Three Submarines,Showing the Outstanding Tasks of the Lost Submarine.

Note: Periods are illustra ve only.

If a successor eet were to operate unbroken patrols with three or eventwo boats, it would have to sacri ce a por on of me dedicated to supportac vi es to maintain this posture. Over a protracted period of me, foregoingrepairs or training to patrol (or provide back-up to a patrol) would eventuallydegrade the reliability of a boat to such a point that patrols would have tobe interrupted whether to train crews, repair submarines, x unexpectedfaults or because of accidents on a patrolling boat. As such, the likelihoodand dura on of any period of inac vity depends heavily upon the number ofsuccessor submarines in a future eet and their individual reliability.

Un l successor submarines have been fully designed, it is challenging toassess exactly how much me will be needed to carry out repairs and traintheir crews. However, reports of the design work conducted so far can shedsome light on the me needed for repairs, if not for training.

Every genera on of submarine so far has required a long period of overhaulto conduct repairs and to refuel the nuclear reactors that power them

(known as Long Overhaul Period (Refuel), or LOP(R)). During these periods,major refurbishment work is conducted on the propulsion reactors, drivesystems, weapons systems and other elements of submarine infrastructure.While the current Vanguard -class submarines require a three-year LOP(R), 26 successor submarines will be equipped with a new reactor (the PWR-3) thatwill fuel each submarine for the en rety of its life me, removing the mostsigni cant element of current LOP(R) procedures. 27

While this will shrink the overhaul period for new submarines, it will notremove it. Given the decision not to adopt more modern (and thereforeless well understood) systems such as electric drive propulsion, successorsubmarines will probably have to undergo at least one major refurbishment


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Figure 4: Poten al Patrol Cycle for a Three-Boat Fleet.

Note: Periods are illustra ve only.

Breaking Covert PatrolsIn todays benign threat environment, a sudden interrup on to the UKscon nuous covert patrols would not have par cularly drama c consequences

for deterrence. However, if an overt interrup on were to coincide withthe emergence of a tangible existen al threat to the UK or its allies, theconsequences would be more severe. In a nuclear- nged crisis, an adversarymay see an interrupted patrol as an opportunity to escalate or even strike.The fear of such a break in patrols may even force the UK into otherwise-undesirable mi ga on ac ons.

Exploi ng Unreliability If an adversary were able to an cipate such an interrup on, this dynamiccould conceivably play a signi cant role in the outcome of a nuclear crisis.In an cipa on of an interrup on, an adversary may have li le incen ve toresolve a crisis quickly (or even prevent one from star ng) when the pa entapplica on of pressure would eventually force the UKs nuclear forcesinto inac vity, weakening its bargaining posi on. More pessimis cally, thean cipa on of such an interrup on may make any overtures towards peacefulreconcilia on by the UK seem like desperate a empts to resolve di erencesbefore its nuclear strength falters. 31 If an adversary were con dent that theUK could not sustain patrols for long and that a break in patrols could beexploited, it may even increase the chances of a nuclear crisis developing inthe rst place.

However, this worst-case analysis does not consider the prac cal factors thatdetermine the likelihood of an interrup on in patrols, and the chances thatsuch an interrup on would fatefully coincide with a period of heightenednuclear tension. While a two-boat eet would not be able to sustain patrolsmuch beyond the beginning of a long overhaul period, it must be consideredhow frequently such overhaul periods might occur. If successor submarinescould be overhauled in only two years, rather than three, only 8 per cent of asubmarines twenty- ve-year lifespan would be spent undergoing overhaul. 32

In the mean me, another ques on is how an adversary would quan fythe rate at which a eets opera on capability declined, increasing therisk of an unexpected interrup on. Crew and technical degrada on does


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not necessarily occur in a smooth and predictable manner, and even if an

adversary had some threshold of presumed reliability under which it mightconsider aggression, it would be challenging to gauge when this thresholdhad been passed. The adversary would nd it similarly di cult to quan fythe chances of a submarine su ering an unexpected and debilita ng faultwhile there was no reserve submarine to replace it. If such an event could bepredicted, it could also be avoided. It is also important to recall here that ifthe current submarine eet can conduct minor repairs whilst s ll on patrol,the same will probably be true of its successor.

The reliability of and repair schedules for the next genera on of submarineshave yet to be determined, and once they are the former would be highly

classi ed and the la er would be exible. There is li le informa on availableto suggest that reserve submarines have been called upon in the past, andeven if they had been, such an incident would never be openly reported. 33 Byop ng for known, opera onally understood systems rather than novel ones(such as electric drive) it is reasonable to suspect that successor submarinesmay ul mately be more reliable than their predecessors. Furthermore, oncethe constraints that CASD imposes on patrolling structures were abandoned,the repair and overhaul schedules of successor submarines could be advancedto coincide with periods of calm, or delayed un l a crisis had passed. Evenperiods of minor repair could be broken up into shorter and more frequenttasks, some of which could be performed whilst deployed.

If all submarines were visibly in port, an adversary would have li ledoubt that there were no opera onal patrols. However, once a boat weredeployed an adversary would have li le informa on from which to judgethe length of its patrol. While an adversary might be able to exploit humanintelligence to this end, its most reliable open source of informa on fromwhich to hypothesise the likelihood of a gap in patrols would ul mately bethe previous behaviour of the successor eet. For instance, if a three-boateet had recently completed a major period of repair, an adversary wouldprobably not an cipate an unavoidable breakdown in patrols within a useful

mescale. However, if a two-boat eet had been sustaining unbroken patrolsfor a long me without undergoing any major refurbishment, an adversarymight suspect a long-overdue repair would soon interrupt this patrol.

This reveals a poten al bene t of a exible approach to nuclear readiness. Ifthe UK were to maintain patrols on a near-con nuous basis (as in the focusedand sustained postures outlined above) irrespec ve of the interna onalthreat environment, it would have li le chance to u lise periods of calm toaddress any developing concerns over reliability or training. On the otherhand, if the UK relaxed its patrol tempo in periods of calm (to lower-readinessarrangements such as the responsive or con ngency postures outlinedabove), it could address any emerging reliability issues before an unfolding


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crisis made them acute. In this la er case, if submarines had to be deployed

this would be done with the lowest possible risk of fault or interrup on.34

Sustaining Patrols in a New Cold War ScenarioThis exibility would not guarantee the reliability of a two- or three-boateet in the longer term. While few nuclear- nged crises in the past havestretched much beyond the dura on of one or two submarine patrols, 35 itis possible that a limited crisis may transform into a drawn-out period ofsustained interna onal poli cal and military tension. As suggested by the TAR,if a crisis were to stretch out over twenty years, even a recently overhauledthree-boat eet would risk mul ple unplanned breaks in con nuous covertpatrolling. 36 Furthermore, a two-boat eet deployed over twenty years

would almost certainly su er a number of breaks over this period.

However, over a twenty-year period of tension, the UK could nd a numberof nuclear or non-nuclear (either military or otherwise) means to mi gatethe emerging threat of a break in nuclear submarine patrols. For instance,if a eet could sustain unbroken patrols for a few years (challenging withtwo boats, but far more feasible with three) the UK could possibly resurrectformer nuclear systems such as the WE-177 gravity bombs that wereabandoned in the 1990s to cover the risk of an inac ve submarine. Thisweapon closely resembles the US B61 gravity bomb, some of which are s llforward-deployed in Europe through NATO mechanisms.

While the TAR suggests that developing alterna ve nuclear weapons for acruise missile may take up to twenty-four years, 37 this mescale would besigni cantly reduced by the familiarity of the WE-177 warhead, the reten onof some of its non-nuclear components, and by relaxing produc on, designand safety criteria in line with its emergency stop-gap nature. This solu oncould even buy enough me to restart inac ve produc on lines and acquirea fourth nuclear-armed submarine to guarantee the maintenance of CASDif deemed necessary. This exibility would cost a signi cant amount of meand money: restar ng produc on lines has proven di cult in the past and

acquiring a fourth boat long a er the rst three would certainly be moreexpensive than if four were procured in quick succession. 38

However, the op on to return to a more con nuous level of nuclear force(either through addi onal submarines or other pla orms) would always bepresent. If there were only a 20 per cent chance that this op on would berequired, refraining from procuring a fourth boat could s ll be considered coste ec ve. Were it to adopt a three-boat eet, the UK could s ll recons tuteits previous nuclear strength if the interna onal environment demanded it.Retaining this op on would further reinforce the deterrent value of a three-boat eet by undermining the chances that an adversary might believe itcould enjoy a nuclear advantage in the long term.


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Transi oning to and from Patrols

As discussed above, the risk of a two- or three-boat eet su ering aninterrup on in covert patrols in a crisis par ally depends upon theopera onal history of the eet prior to the crisis. If a eet were normallyheld in port, rolling repairs would ensure submarines were deployed withthe lowest possible risk of mechanical or personnel failure. However,postures in which the UK rarely sends its submarines to sea (such as thecon ngency and preserved postures) raise two important ques ons: thecircumstances under which the UK would change the status quo and deploynuclear-armed submarines, and how this ac on might a ect the behaviourof its adversaries. Having deployed its submarines, the UK would also nditself ques oning under what circumstances it might withdraw them. While

a premature withdrawal might reignite an adversarys enthusiasm foraggression, maintaining unnecessary patrols could exhaust the eets abilityto meet resurfacing threats.

Both the deployment and withdrawal of nuclear submarines could sendpowerful signals to the interna onal community. If the UK were to feelthreatened, deploying its submarines would remind its adversaries that theUK was prepared for a crisis that might eventually bring it to the nuclearbrink. In an cipa on of an acute threat, early deployment could also removean adversarys incen ve to ini ate hos li es while the UKs submarines werevulnerable. If such a threat were to recede, visibly withdrawing submarineswould show the UKs adversaries that it felt no need to sustain a short-no cestrike capability, and was comfortable enough to assume that a bolt from theblue was highly improbable. 39 The Labour government was keen to outlinethis signalling dynamic in its 2006 defence White Paper, which argued that itis especially important during a crisis to both overtly and covertly increaseor decrease the readiness of its nuclear forces to provide the most exibilityin posture. 40

It can be argued that in both cases the intended signals can have unintendedconsequences. Whether or not an adversary intended to threaten the UK,

visible e orts to deploy submarines might come across as prepara ons tolaunch a nuclear strike, promp ng an adversary to escalate by pre-emp velya acking the UKs forces (either by conven onal or even nuclear means)before they became opera onal. The visible cancella on of unbrokenpatrols could be seen more as an act of technical necessity rather than oneof reassurance, presen ng an aggressor with an opportunity to escalatewithout fear of nuclear reprisal.

Further, the security dilemma in this case, that the defensive deployment ofa submarine might trigger an avoidable con ict could paralyse UK decision-makers. If an adversary came to expect this paralysis, the credibility of theUKs deterrence would be signi cantly degraded.


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In prac ce, these signalling dilemmas greatly simplify the manner in which

the UKs readiness might be calibrated and the responses such ac ons mightprompt.

First, an adversary would not see the deployment or withdrawal of submarinesin isola on. Rather, there would be a deluge of other informa on such asdiploma c, intelligence and personal sources as a crisis evolves. Accordingto Keren Yarhi-Milo, decision-makers inclina on to rely on their own

judgements and subjec ve readings of signals to infer poli cal inten ons ispervasive and universal. 41 As such, the signi cance (intended or otherwise) ofarmed-submarine deployment or withdrawal in a crisis might be emphasisedby an adversarys intelligence agencies that are designed to iden fy military

threats, but downplayed by decision-makers in favour of other informa on.In many previous cases such as 1971 IndoPakistani War and the 1973 YomKippur War the purposefully overt raising of the readiness of US nuclearforces proved to have li le impact on, or was super uous to, the resolu onof a crisis. 42

If patrolling pa erns were frequently changed with li le obvious regard tothe interna onal environment, even the most carefully calibrated change inthe future might be dismissed by adversaries as simply scaremongering ora blu . On the other hand, as any period of sustained patrol or inac vitylengthened, with few adjustments made in response to changes in theinterna onal environment, any subsequent change to patrols would bea stark break in the norm, unavoidably amplifying its signi cance in anadversarys calculus. This would be most acute in the highest- and lowest-readiness postures (such as a focused deterrent or a preserved deterrent),which maintain either deployment or inac vity as the status quo. 43

In the case of lowest-readiness postures, the occasional deployment ofsubmarines for training purposes (as envisioned in the Liberal Democratscon ngency posture) must be taken into account. The proceduresassociated with calibra ng the readiness of nuclear submarines (such as

reactor ac va on, warhead loading, or even submarine deployment) wouldhave to be exercised occasionally to ensure they remain safe and e cient,dilu ng the impact of any single deployment process and o ering a less-threatening interpreta on to any concerned adversary. While there is nodirect corollary for postures which normally maintain boats on patrol, abreak from this norm is unlikely to provoke new aggression.

Second, submarines can be held at varying levels of readiness. As a crisisloomed, submarine reactors could be ac vated within a day or two, crewscould be mustered, and provisions loaded without actually launching thesubmarine. For instance, even if submarines were not deployed, a sustainedposture would maintain one submarine on deterrent duty and ready to


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deploy swi ly, 44 perhaps by keeping its reactor online or by a host of other

measures. Similarly, cancelling submarine patrols would not necessarilyplace submarines far beyond re-use; a signal of vulnerability could be sentwithout reversing all of the deployment steps described above.

Rather than being faced with a single terrible choice, as a crisis emergedor receded the government would be faced with an array of choices withinac vity at one extreme and the rushed deployment of armed submarinesat the other. Choosing which (if any) steps to take may not be easy; calibra ngthe readiness of nuclear forces in such a way would be en rely unfamiliar tothose accustomed to the simplicity of CASD. 45 Rather, these choices wouldprovide decision-makers with more nuanced responses to an evolving

interna onal threat environment.

With this in mind, if the UK adopted a non-con nuous patrolling posture,not only would it have to consider when it would deploy its submarines,it would also have to consider how to deploy these submarines, and howto integrate this change in readiness into its broader foreign policy. The co-ordina on or lack thereof between any adjustment in nuclear readinessand broader signals of intent (such as declaratory posture or rhetoric) wouldplay a greater part in crisis management than the deployment itself.

As such, the stability of any transi on to or from patrolling will ul mately bedetermined by the UKs ability to consider these ques ons and implement theanswers in a reliable yet exible manner. No ma er how well a deployment isportrayed on the interna onal stage, if such a move were poorly executed byan ill-prepared crew it could s ll destabilise an emerging crisis or, worse s ll,cause a nuclear accident. Developing a exible yet reliable system throughwhich to respond to an emerging crisis would be challenging, given that thesetwo characteris cs are not always mutually reinforcing, and communica onbetween those that manage patrols and those that manage diplomacy iso en imperfect.

A Bolt from the Blue?The success of this exible approach to submarine readiness would dependupon a rela vely sophis cated understanding of an adversarys inten onsand fears. While current assessments declare that no state is willing and ableto threaten the independence or integrity of the UK, this may not be the casein the future. By monitoring the submarines and training ac vi es at theUKs naval base in Faslane, one can imagine an unknown adversary covertlydeveloping an impression of how quickly the UK could deploy its submarinesin the event of an imminent a ack. Such an adversary might feel temptedto exploit this window of vulnerability by striking the UKs forces out of theblue.


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If the UK were unaware of this threat, it would have li le chance to prepare

a response. Deploying an inac ve submarine would not be instantaneous:it would likely be fraught with di cul es both technical and human. 46 Without any prior prepara on aside from training, current deploymentprocedures would require a submarine to be ac vated, loaded with supplies,checked over, carefully armed with up to forty warheads, and then pilotedto a safe patrolling zone. In all, these ac vi es take up to two weeks tocomplete. 47

In a straight race from a standing start, a determined and suitably equippedadversary with ready forces could certainly strike the UKs nuclear forcesbefore they had a chance to deploy. There is no silver bullet for dealing

with this problem. If the UK drama cally altered the current deploymentprocedures (for example, by reloca ng submarines to the warhead depot atCoulport and re-designing the arming procedure) it might be able to reducethis cold start me. However, making such readjustments to the exis ngsubmarine infrastructure would be very expensive (and poten ally unsafe),and such drama c measures were not considered in the TAR. Furthermore,modern ballis c missiles can strike their target in approximately thirtyminutes, leaving li le me for even the best-prepared submarine to deployto a safe distance.

A Part-Time Deterrent? While the UK could never guarantee the survivability of an inac ve submarineeet, it might never have to do so. Despite cri cism that non-con nuouspostures would create a part- me deterrent, 48 even an inac ve eet ofsubmarines can help to deter actors from seriously threatening the UK. If itwere seen to be capable of deploying its nuclear forces in a crisis, the veryexistence of such a force could have the e ect of dissuading a poten allyhos le state from threatening or blackmailing the UK and its allies. With thisin mind, the visibility of deployment exercises might reinforce this recessedform of deterrence.

Furthermore, a pre-emp ve strike against inac ve nuclear forces (throughconven onal or nuclear means) would be an extremely dras c move. Aserious threat to the UK would not come out of the blue in this way. It ishighly unlikely that an adversary would consider a surprise a ack withoutpassing through some prior period of overt tension that could alert the UKto this threat. Indeed, even at the height of the Cold War, the UKs transi onto war exercises assumed that a nuclear crisis would emerge over a month,rather than a couple of weeks, and included mul ple indica ons of a poten alnuclear threat. 49

In the unlikely event that this threat emerged without any warning, anaggressor would have to be extremely bold to ignore the probability that such


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pre-emp ve aggression would be met with stern punishment from sources

other than the UK, which is likely to remain a member of NATO. Even in theunlikely scenario that the UKs rela onship with the US has seriously andvisibly deteriorated (and the credibility of NATOs shared nuclear deterrenceis ques oned), an aggressor might s ll fear severe punishment by nuclear-armed states wishing to discourage unprovoked counter-force a acks onnuclear capabili es. 50 As noted earlier, even a modest chance of a hugepenalty can have great deterrent e ect. 51

This is not to say that a non-con nuous eet would be immune to a bolt-from-the-blue a ack. Rather, such an a ack would only become plausible ifthe interna onal environment soured drama cally. This would not happen

overnight, but it is s ll possible that the UK might miss important indica onsof tension, or register such indica ons but avoid responding for fear ofcontribu ng to the risk of inadvertent escala on. However, if the UK couldsuccessfully gauge the interna onal threat environment, it would have manyopportuni es to co-ordinate a response and calibrate the readiness of itsnuclear forces.

A Break from the NormIf the UK were to break a forty- ve-year tradi on and abandon CASD, itsnuclear forces would s ll present a threat to current and future adversaries.Even if this doctrinal change were accompanied by a reduc on in the size ofits future submarine eet from four to three boats, the UK would s ll be ableto sustain seamless, unbroken patrols for an extended period of me. Thisperiod would not be inde nite, and the risk of unavoidable interrup onswould grow as these patrols dragged on. However, this risk would be verylow during the rst decade of each submarines life me (in the case of thesuccessor, from 2028 towards 2040). Even a er that date, without the abilityto quan fy its growth over a me, adversaries are unlikely to see this risk asan incen ve for aggression. Only the most reckless adversary would embarkon a hos le pathway under the assump on that it could control a crisis wellenough to prompt and subsequently take advantage of a break in patrols.

Even if such a foe did exist by the 2040s, the UK would have a number ofmi ga ng op ons.

During periods of lower tension, the eet could cancel sustained patrolsand return to port without incurring any substan al risks of automa callypromp ng an opportunis c strike or sacri cing its ability to deter. An inac veeet would be vulnerable to a no-no ce strike, and could neither protectitself against nor respond to an a ack under these circumstances. However,such an a ack seems highly unlikely without prior indica on or provoca on,both of which would provide the UK with an opportunity to calibrate thereadiness of its forces. When considering an a ack in this way, an adversarywould have to calculate that the response from the UKs allies, or even the


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wider interna onal community, would not outweigh the bene ts of a surprise

strike. The interna onal opprobrium that such a strike would create, and thecompara vely small gains it might produce while the US remains the worldsdominant military power, suggests this bargain would not be easily made.

By visibly training and exercising the deployment of inac ve submarines,the UK would be able to reinforce the impression that its nuclear forcescon nued to present a potent threat at rela vely short no ce. In muchthe same way that conven onal forces held in reserve present a deterrentthreat, so could a three-boat eet of nuclear submarines held in reserve.In this sense, nuclear forces that are voluntarily kept inac ve should not beseen as a part- me deterrent.

If the UK were to abandon CASD and take steps down the nuclear ladder ofcapability and readiness, moving back up this ladder to a period of sustainedpatrols might not automa cally trigger a spiral of escala on. While prominentapproaches to interna onal rela ons suggest that an adversary would

judge the UKs inten ons primarily on changes to its military capabili es, arecent study of past crises suggests that an adversary is more likely to judgeinten on not on military capabili es, but on a subjec ve interpreta on ofa number of signals, including personal rela onships and ideologies. 52 Thedecisive nuclear factor in the escala on or de-escala on of a crisis wouldtherefore not be the deployment or withdrawal of nuclear forces alone, butthe manner in which such a move is carried out and integrated into broaderdiploma c signals.

The risks associated with ac va ng and deac va ng nuclear submarines(whether voluntarily or otherwise) must be placed in this broaderinterna onal context, in which rela onships between adversaries aredetermined by far more than the condi on of nuclear forces. Changesin nuclear strength will be only one element of the mul faceted causalrela onships that ul mately determine the outcome of hos li es, and co-ordina ng diploma c, military, economic and ins tu onal messages has

long been a central issue in interna onal rela ons.53

Nuclear Novelty However, the co-ordina on of nuclear and non-nuclear signals has notbeen central to the UKs nuclear strategy for a very long me. By its verynature, con nuous at-sea deterrence rules out a number of adjustments theUK might make to signal to its adversaries. Indeed, despite the last Labourgovernments asser ons about the importance of overtly raising and loweringthe readiness of its nuclear forces, 54 the UK has had very li le opportunity tosend nuclear signals since it abandoned the airborne element of its nuclearforces in the late 1990s. 55 While airborne forces can be visibly redeployed tothreaten speci c targets (as the US did during the Berlin Crisis and Korean


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War, and as the US o en does today to send signals to North Korea), it is hard

to make threatening gestures with invisible submarines.

In that sense, the immutability of CASD disengages nuclear forces fromthe day-to-day management of interna onal rela ons. While crises mayerupt and recede, the UKs nuclear forces con nue their patrols unchangedand would only play a part in crisis management in the most extremecircumstances. Decisions over the readiness and potency of the UKs nuclearforces are primarily constrained to periodic posture reviews, which take astrategic (rather than tac cal) view of the interna onal threat environment.

Adop ng a exible approach to non-con nuous postures, in which the UK

would calibrate its forces from high to low readiness, would require the UKto consider the status of its nuclear forces on a more frequent basis. In theface of an evolving crisis, the UK would need to take a number of decisionsover whether and how to ini ate, sustain and ul mately terminate extendedperiods of patrolling decisions that are currently unfamiliar. Furthermore,these steps would have to be carefully integrated into broader e ortstowards crisis resolu on.

While the UK maintains con nuous deployments, there is li le reason toview emerging threats in terms of a required level of nuclear readiness;this has already been set. If the UK adopted a non-con nuous posture,however, any emerging threat above a certain threshold would necessarilybe seen through a nuclear lens. Should this threshold be crossed on aregular basis, a non-con nuous nuclear force would not de-couple nuclearweapons from the day-to-day calculus of na onal security; 56 instead, itwould pollute areas of decision-making where it was previously of li lerelevance.

In this case, a key challenge to abandoning con nuous at-sea deterrence maynot be the preserva on of credible nuclear threats, but the developmentand implementa on of organisa onal structures that would allow decision-

makers the me, freedom and con dence to calibrate nuclear forcesin response to emerging threats. At the poli cal level, overt changes tonuclear readiness may have to be explained not just to the public, but alsoto the UKs adversaries and allies. At the opera onal level, the current rigidand well-prac sed structures for deployment and repairs would have toevolve to accommodate a more exible approach whilst simultaneouslymaintaining the safety and security of the UKs nuclear forces. Technicalreali es may make it challenging to break down large-scale repairs intosmaller, more exible packages, and while adjustments to the currentopera onal infrastructure may mi gate this, these may not come cheap.


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will only require a deployed nuclear deterrent on rare occasions. In this

case, if the UK can implement a exible structure in which to operate anon-con nuous nuclear force without sacri cing any nancial or poli calgains it hopes to make, a step away from CASD could be one of severallegi mate pathways in the UKs nuclear future.

Hugh Chalmers is a Research Analyst within RUSIs Nuclear AnalysisProgramme. Hugh has previously worked at the Veri ca on Research,Training and Informa on Centre (VERTIC), IHS Janes, and the Kings CollegeLondon Centre for Science and Security Studies.

The author would like to thank his colleagues Andrea Berger and Professor

Malcolm Chalmers, whose insights and feedback were instrumental in the produc on of this paper. Furthermore, thanks are due to both Ashlee Godwinand Adrian Johnson for their pa ence and keen editorial eyes. Specialthanks are also due to the many individuals who took the me to discussand comment upon earlier dra s of this paper. Finally, RUSI is grateful tothe Nuclear Threat Ini a ve (NTI), whose generous support made this paper

possible.

Notes and References

1. Michael Quinlan, Thinking About Nuclear Weapons: Principles, Problems, Prospects

(Oxford: Oxford University Press, 2009), p. 24.

2. For a more detailed es mate of through-life costs and their consequences see MalcolmChalmers, Towards the UKs Nuclear Century, RUSI Journal (Vol. 158, No. 6, December2013).

3. HM Government, Trident Alterna ves Review, July 2013.

4. David Blagden, Reducing Britains Nuclear Capability Would be a Grave Mistake,Guardian , 1 July 2013.

5. Franklin C Miller, The Future of the United Kingdoms Nuclear Deterrent, RUSI Journal

(Vol. 155, No. 2, April/May 2010), pp. 3439.

6. Nick Ritchie and Paul Ingram, A Progressive Nuclear Policy: Rethinking Con nuous-At-Sea Deterrence, RUSI Journal (Vol. 155, No. 2, April/May 2010), pp. 4045.

7. For instance, the Trident Alterna ves Review gives four possible postures. See HMGovernment, Trident Alterna ves Review, p. 23.


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8. On average, the US maintains eleven of its fourteen nuclear ballis c-missile submarines

at sea at any one me. Hans M Kristensen, Declining Deterrent Patrols Indicate TooMany SSBNs, FAS Strategic Security Blog, 30 April 2013.

9. Hans M Kristensen and Robert S Norris, Russian Nuclear Forces, 2013, Bulle n of the Atomic Scien sts (Vol. 69, No. 3, May 2013), p. 76.

10. Tim Hare, Nuclear Policy at Sea: A Part-Time Deterrent Will Not Do!, RUSI Journal

(Vol. 154, No. 6, December 2009), p. 54.

11. HM Government, The Strategic Defence Review , Cm 3999 (London: The Sta oneryO ce, July 1998), p. 27.

12. HM Government, Trident Alterna ves Review, p. 24.

13. Ministry of Defence, The United Kingdoms Future Nuclear Deterrent: The SubmarineIni al Gate Parliamentary Report, May 2011, p. 4.

14. HM Government, Trident Alterna ves Review.

15. Je rey Lewis, The Minimum Means of Reprisal: Chinas Search for Security in theNuclear Age, PhD thesis, , accessed 8 January 2014. Emphasis added.

16. Mark A Stokes, Chinas Nuclear Warhead Storage and Handling System, Project 2049Ins tute, 12 March 2010, p. 12.

17. For examples see Sumit Ganguly, Nuclear Stability in South Asia, Interna onalSecurity (Vol. 33, No. 2, Autumn 2008), pp. 4570; John Arquilla, Nuclear Weapons inSouth Asia: More May Be Manageable, Compara ve Strategy (Vol. 16, No. 1, 1997),pp. 1331.


19. Ibid. ; Malcolm Chalmers, Con nuous At-Sea Deterrence: Costs and Alterna ves, RUSIBrie ng Paper, July 2010.

20. Danny Alexander, speech given at the Royal United Services Ins tute, London, 16 July2013, , accessed 8 January2014.

21. Liberal Democrat Party, Defending the Future: UK Defence in the 21st Century, PolicyPaper 112, Autumn 2013, p. 19, , accessed8 January 2014.


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34. Even with the most rigorous maintenance and training, one cannot rule out the

possibility that unknown weaknesses or human error could interrupt a patrol.

35. The Suez Crisis (1956), the Cuban Missile Crisis (1962) and the Able Archer nuclearcrisis (1983) all lasted only a ma er of days. More protracted crises between nuclearpowers such as the SinoSoviet border crisis (1969), the Kargil War (1999), and the2011 IndiaPakistan stand-o all lasted fewer than six months.

36. If this were not the case, a three-boat eet could e ec vely maintain CASD. HMGovernment, Trident Alterna ves Review, p. 37.

37. Ibid.

38. Delays in procuring long-lead items would prevent the UK from tes ng non-con nuouspostures during the current submarine acquisi on meline which assumes a fourthboat will begin construc on in 2023.

39. The Soviet Union, and later Russia, a empted to send just such a signal to the US whenit purposefully grouped its mobile missile launchers in vulnerable sites during the 1991coup against Gorbachev and following the 9/11 a acks in New York and Washington, DC.

40. HM Government, The Future of the United Kingdoms Nuclear Deterrent , Cm 6994(London: The Sta onery O ce, December 2006), p. 22. Emphasis added.

41. Keren Yarhi-Milo, In the Eye of the Beholder: How Leaders and Intelligence Communi esAssess the Inten ons of Adversaries, Interna onal Security (Vol. 38, No. 1, Summer2013), pp. 751.

42. Rebecca Davis Gibbons, Signals Intelligence? The Eec veness of Nuclear andNonnuclear Signals in a Crisis, in Center for Strategic and Interna onal Studies, ACollec on of Papers from the 2011 Nuclear Scholars Ini a ve, December 2011, p. 68.

43. Medium-readiness postures such as the sustained and responsive postures outlined

in the TAR would be less suscep ble to misinterpreta on by an adversary, as they bothinvolve the periodic deployment and withdrawal of submarines.


45. In contrast, the UK o en has to consider the interna onal implica ons of overt changesin readiness of its conven onal forces.

46. Hare, Nuclear Policy at Sea, p. 54.

47. To keep health and safety risks as low as reasonably prac cable (the ALARP principle)warheads are currently transported and ed to missiles one at a me.


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48. Hare, Nuclear Policy at Sea, p. 57.

49. Peter Hennessy, The Secret State: Preparing for the Worst 19452010 , 2nd edi on(London: Penguin, 2010), pp. 21757.

50. Both China and Russia have raised serious concerns regarding US conven onal PromptGlobal Strike programmes, whose mission may include pre-emp vely striking nuclearforces with conven onal muni ons. See James M Acton, Silver Bullet? Asking theRight Ques ons about Conven onal Prompt Global Strike, Carnegie Endowment forInterna onal Peace, September 2013, p. 120.

51. Michael Quinlan, Thinking about Nuclear Weapons, RUSI Whitehall Paper (No. 41,

1997 and 2005), p. 24.

52. Yarhi-Milo, In the Eye of the Beholder.

53. For instance, see Robert Jervis, Percep on and Mispercep on in Interna onalRela ons (Princeton, NJ: Princeton University Press, 1976).

54. HM Government, The Future of the United Kingdoms Nuclear Deterrent , p. 22.

55. The UK sent a veiled nuclear signal prior to the Iraq War in 2003, when DefenceSecretary Geo Hoon told the BBC that the UK was willing to use nuclear weaponsin the right condi ons. However, there was li le visible manifesta on of this threat.See BBC News , UK Restates Nuclear Threat, 2 February 2003.

56. Liberal Democrat Party, Defending the Future, p. 21.

57. Ministry of Defence, Top Level Messages October 2013, p. 15, , accessed 9 January 2014.

58. Robert Burns, Study: Nuclear Force Feeling Burnout from Work, Associated Press ,

21 November 2013.

59. Will Dahlgreen, Public Support for Nuclear Weapons, YouGov.co.uk, 16 July 2013,,accessed 9 January 2014.


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A Disturbance in the Force: Debating Continuous at-Sea Deterrence (RUSI report, January 2014)