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Mind the Gap: Strategic Risk in the UK’s Anti-Submarine Warfare Capability

Commentary, 4 February 2011
Defence Management, Defence Policy, Domestic Security, Maritime Forces, UK Defence, Europe
Footage of JCBs turning Nimrods to scrap metal reflects the drastic nature of recent cuts in the defence budget, but seemingly straightforward changes can have far-reaching implications for UK defence policy.

Footage of JCBs turning Nimrods to scrap metal reflects the drastic nature of recent cuts in the defence budget, but seemingly straightforward changes can have far-reaching implications for UK defence policy.

by Lee Willett for

Nimrod, MR2, Crown Copyright
Nimrod MR2, withdrawn in 2010, a precursor to the now-scrapped MRA4. (Image: RAF, Crown Copyright)

The Government's decision to withdraw its maritime patrol aircraft (MPA) capability by scrapping the Nimrod Maritime Reconnaissance and Attack (MRA) 4 programme has proved to be one of the more controversial decisions relating to the UK's maritime capability in the Strategic Defence and Security Review (SDSR).[1] Protecting high-value assets and interests at sea requires specific military capabilities, and the withdrawal of the UK's only long-range strategic MPA asset has presented the UK with some difficult decisions and some serious risk.

In January 2011, implementing the decision to scrap Nimrod began with what has become an iconic image of the consequences of the SDSR, spending cuts and procurement time and cost overruns: the deconstruction - by JCBs - of the first three of the planned nine MRA4s. The UK has lost a state-of-the-art, UK-designed and -built asset. It has also lost one of the key layers in its security architecture, an asset which could play a role in anything from countering insurgency in Afghanistan to monitoring Somali piracy and Olympic security. On the back of a series of events in 2010 which demonstrated the strategic importance of maritime power to the UK, perhaps the most significant event which took place was one which received relatively little attention, but which - given the Nimrod decision - demonstrated a clear risk to UK national security interests.[2]

In the Event of a Submarine Incursion ...

In the week the SDSR was announced, the Daily Record reported, on 22 October, that '[a]s Prime Minister David Cameron announced that he was cancelling the Nimrods on Tuesday [19 October], an American P3 was beginning a hunt for a Russian submarine in the Atlantic.'[3] In fact, a pair of United States Navy P3 Orion anti-submarine warfare (ASW) aircraft diverted from the NATO Exercise JOINT WARRIOR, off the Scottish coast, to hunt for an Akula-class nuclear-powered attack submarine (SSN) which was apparently attempting to sneak into UK waters. An MoD spokeswoman said: 'US P3 Orion aircraft have been at RAF Kinloss participating in a NATO exercise. ... The UK routinely operates alongside our allies, including the US and France, when conducting joint maritime patrol activities and will utilise a range of other military assets to ensure the integrity of UK waters.'[4] Relying on other assets, whether national assets or those of other nations, assumes spare capacity exists when other priorities have been addressed.

The P3s are extremely capable aircraft, but do not possess the technology of an MRA4. The P3s will be replaced, starting in 2018, by the P8A Poseidons. The MRA4s had not yet entered into service, so were unavailable. The task would have been the responsibility of their predecessors, the Nimrod MR2s. However, the MR2s were withdrawn from service in April 2010 following the tragic loss of an MR2 and its fourteen crew over Afghanistan in September 2006.

The SDSR did not explain the decision to withdraw Nimrod, stating simply that the UK would 'not bring [the MRA4] into service'.[5] It stated, though, that the future security environment the UK would face would 'place a premium on particular military capabilities, including intelligence, surveillance, targeting acquisition and reconnaissance (ISTAR).'[6] While Nimrod's problems have been well-documented, the fact that the Government reinforced the need for ISTAR capability while not explaining why an MPA did not meet it raises the possibility that the SDSR carefully left the door open for a potential P8 purchase in due course.

The apparent Russian submarine incursion is not a new issue. For several years, Russian Bear MPAs have been probing Western airspace, such visible activity demonstrating capability - if not intent - to both international and domestic audiences. Many nations see submarines as a way of 'jumping the queue' in terms of the strategic influence of their navy and their nation.[7] Russian President Vladimir Putin sees submarines as critical to re-generating Russian strategic influence. Thus, it seems logical that Russia would be sending boats out into the Atlantic again, and perhaps that it has been doing so for some time.[8] By the summer of 2009, there was no longer any need to speculate. In August that year, a pair of Akulas was reportedly located 200 miles off the US Eastern Seaboard.[9] By the summer of 2010, the issue had become public in the UK. The Daily Telegraph reported that, with Russian submarine activity around UK waters reaching levels not seen since 1987, Akulas were attempting to track VANGUARD-class ballistic missile submarines (SSBN) which embark the UK's nuclear deterrent and that, in one instance, an Akula had attempted to station itself off the VANGUARDs' home port of Faslane, intending to track a particular VANGUARD boat as it sailed.

Such incursions remain occasional, and the intent is unclear. However, the apparent focus on the UK's deterrent highlights the significant risk to national interests.

Anti-Submarine Warfare: A Layered Capability

Developing an effective ASW capability requires the inter-weaving of several layers of capability. Each layer fulfils a particular function, making a particular contribution to the overall effectiveness of the ASW web. Yet, with the submarine threat to the UK much reduced since the Cold War and with the UK now focused elsewhere, some argue that the ASW requirement has also reduced. Certainly, the UK's ASW capability has dwindled in terms of significance as well as systems and skills sets.

The UK's ASW layers have thus been steadily eroded. The Nimrod decision, however, has highlighted quite starkly and suddenly the consequences of this. Despite MoD statements that Nimrod's roles will be covered by other assets, no other assets deliver its specific capabilities. The UK's ASW web hence has a particular, and significant, hole in it.

Maritime Air

In Nimrod, the refined sensor capabilities - both actual in the MR2 and planned in the MRA4 - together with the aircraft's range, speed and endurance, gave the UK an asset which could operate from strategic to tactical levels. Operating in all three environments - air, surface and sub-surface - it could reach targets, even distant ones, quickly and could maintain pressure on the target while vectoring in other assets.

The air gap will be filled at the tactical level by the Royal Navy's Merlin HM1 ASW helicopter and its AQS-950 dipping sonar. Required to prosecute a submerged target quickly, Merlin operates out ahead of its host platform, a DUKE-class Type 23 frigate. The Royal Navy will have around 40 Merlins, scheduled to stay in service until 2029. Along with the already-planned retirement of the Sea King Mk7W and Lynx helicopters, withdrawing Nimrod may place a premium on Merlin numbers. What is far from clear is if and for how long these numbers can survive sustained spending cuts.

Surface Forces

The Type 23 is the Royal Navy's dedicated surface ASW asset. It also appears to be shouldering most of the post-Nimrod capability gap burden. Armed with its Merlins and a 2087 towed array sonar, it has the capability both to sanitise the waters ahead of a VANGUARD boat departing or returning to Faslane - something known as 'de-lousing' - as well as tactical prosecution of suspect contacts.

However, there are consequences in relying upon a Type 23 as the primary ASW asset for deterrent protection. Firstly, the Type 23/Merlin package does not match Nimrod's capability. Secondly, placing a surface asset conducting ASW de-lousing patrols may be perceived as indicating the SSBN's location. Thirdly, again there is the numbers question. Under the SDSR, the UK surface flotilla is sinking from twenty-three to just nineteen platforms - thirteen Type 23s plus the six DARING-class Type 45 destroyers. It has been reported by the Financial Times that, to balance the SDSR's books, a Type 23 may be withdrawn. The Type 23s will be the surface fleet's workhorses. However, with only a handful likely to be available at any one time and with a range of global taskings to meet, dedicating a Type 23 to protecting the deterrent means other tasks will have to be gapped.

The Type 45s all will be in service shortly. Although equipped with a Merlin and an extensive command and control suite, these ships are air defence rather than ASW platforms. They will most likely be tasked with the close-in defence of a Task Group and its high value asset, such as a QUEEN ELIZABETH-class carrier or an amphibious ship. Moreover, without a 2087 capability, its sonar capacity is limited. Whether it was protecting a carrier or an SSBN, detection of a submerged contact on sonar would suggest that the threat was already far too close.

The Type 26 frigate, the UK's indigenous variant of the Global Combat Ship concept, will replace the Type 23s as a multi-purpose but primarily ASW platform. Currently, little is known publicly about its capabilities. However, given the streamlining in the number of surface ship classes, the intended flexibility in the Type 26 concept, design and capability will have to be maximised to ensure the ships can undertake a wide range of roles. Even if the economy has recovered to some degree in time, it still seems aspirational at best to think that UK defence spending will increase after 2015. Thus it seems unlikely that surface fleet numbers will rise above nineteen in the medium term.

Moreover, as the cost and capability pendulum swings back and forth - as expected, at this stage in a programme - it remains unknown if and to what extent planned capabilities will be scaled back to reduce cost. Some have argued that reducing unit cost could help underwrite the case for more numbers. Continuing financial pressures suggest, however, that any reduction in unit costs simply will underwrite the spending cuts instead. It is hence not clear how much of an ASW focus on deterrent protection the deterrent Type 26s will have.


In the post-SDSR ASW capability gap debate, the spotlight has fallen primarily on Nimrod. Arguably, though, the UK's primary ASW capability remains its SSNs. The degradation of the UK's SSN ASW capability and skills set has been an issue since the end of the Cold War. With the disappearance of the Russian submarine threat, the SSN's covert capabilities were diverted to different tasks, such as counter-narcotics, counter-terrorism and special forces insertion. Their capabilities were also augmented, with Tomahawk cruise missile land attacks becoming their primary role.

However, there are still questions about the SSNs' enduring contribution. The loss of submariners' ASW skills remains a significant concern - although it should be noted from the Daily Telegraph report that, rather than the Russian submarine tracking a VANGUARD boat and recording its unique acoustic signature, in fact the TRAFALGAR-class SSN sent to look after the VANGUARD not only found but also got an acoustic recording of the Akula.[10]

The Royal Navy's four core strategic contributions to UK defence policy - the deterrent, Carrier Strike, amphibious operations, and Tomahawk land attack - all are enabled by SSNs and by ASW in particular. Since the end of the Cold War, the attack submarine flotilla has been cut by more than half to just seven boats, a force level which has been in place since December 2007.[11] With the need to protect high-value units such as the carriers and amphibious assets, carry out land attack operations and gather strategic intelligence, the demands on SSN numbers will be extremely acute. One of the distinct benefits in the SDSR for the Royal Navy was the commitment to seven ASTUTE-class SSNs. In the SDSR debates, the SSN was notable only by its absence, one brought about by the acknowledgement that, should the UK wish to remain a nuclear power, no fewer than seven ASTUTEs must be built to ensure that sufficient industrial capacity remains until steel is cut on the first new SSBN. Yet one factor in the calculation which produced a force level of seven SSNs back in 2007 was the UK's MPA capability - a capability which no longer exists. Perhaps the primary reason for maintaining - or even increasing - SSN numbers is to fill the ASW capability gap.

Moreover - alongside what appears to be a strategic requirement to maintain one SSN permanently on station east of Suez to meet a range of tasks to which an SSN makes a unique contribution - the ASTUTE boats will be such a potent asset with TLAM, special forces capability and the requirement to protect the high-value fleet units that there may not be enough SSNs available to commit one to protecting the deterrent. The role of the TRAFALGAR-class boat in tagging and taping the Akula demonstrates the risk here. Seven SSNs may simply not be enough.

The submarine threat is a significant national security issue, not just a Cold Warrior's hangover. The UK remains committed to a minimum independent strategic nuclear deterrent. Whether it is a Russian Akula or another nation's submarine showing an interest, the single SSN supporting the deterrent is a critical strategic asset.


An effective ASW capability is not just about protecting the deterrent. Simply because the oceans remain largely impermeable, the simple - confirmed or otherwise - presence of a submarine (no matter how capable and no matter how well driven) can deny the use of a certain sea space because the risk of operating a strategic asset there is too great. With many nations investing in submarine capabilities, the UK has other critical strategic vulnerabilities - such as commercial shipping transiting key maritime choke points around the world, or sea-based logistics chains supporting expeditionary operations such as in Afghanistan - which a submarine is could easily expose and exploit.

Each individual capability layer contributes to a total ASW effect which, arguably, is greater than the sum of the individual parts. Removing one layer can have a disproportionate effect on the overall capability. Nimrod is perhaps the prime example here, operating as the key node at the centre of the ASW web, and able to monitor and provide effect in all environments simultaneously from a single platform. Each layer has the same broad operating principle - locating and identifying contacts at distance, and then bringing in other assets in support. An MPA capability, however, is the glue that binds the layers together into a cohesive ASW cover. Whether creating gaps in the deterrent protection layers or pulling assets off other tasks to fill these gaps, the Nimrod decision has raised some significant questions about the UK's ASW capability.



[1] The SDSR brought some significant strategic gains for the maritime component, committing to two QUEEN ELIZABETH-class aircraft carriers, the Joint Strike Fighter aircraft, and seven ASTUTE-class attack submarines. Yet there was also some significant short-term pain to swallow as well as the cancellation of Nimrod, with the loss of two INVINCIBLE-class aircraft carriers and their Harrier jets, four surface ships, an amphibious ship and an auxiliary ship.

[2] January: The UK's increasing risk of gas shortage underscored the importance of naval forces deployed at distance around the world to ensure that key maritime sea lines and choke points remain open. February: The initial international disaster response to the Haiti earthquake was mounted from the sea as no infrastructure was available ashore. March: The Royal Navy was reported to be reinforcing the UK's deterrent presence in the South Atlantic as resource exploration began in UK waters around the Falkland Islands. April: HM Ships ALBION, ARK ROYAL and OCEAN were employed as part of the effort to repatriate UK nationals stranded abroad by an ash cloud from an Icelandic volcano which closed European air space.

[3] See also Brian Larcombe, 'Russian Around', The Sun, 23 October 2010. Available online, accessed 23 October 2010.

[4] Ironically, of course, Kinloss is the home base of the Nimrods.

[5] Ministry of Defence (MoD). 'Securing Britain in an Age of Uncertainty: the Strategic Defence and Security Review'. Presented to Parliament by the Prime Minister by Command of Her Majesty. Command 7948. Norwich: The Stationery Office (TSO). p.27, para 2.A.11. Available online.

[6] MoD. 'Securing Britain in an Age of Uncertainty: the Strategic Defence and Security Review'. Op. Cit., p.27, para 2.A.11.

[7] See, for example: Andrew Davies, 'Up Periscope: The Expansion of Submarine Capabilities in the Asia-Pacific Region', RUSI Journal, vol.152, no.5, October 2007.

[8] For discussion, see Lee Willett, 'The Navy in Russia's Resurgence', RUSI Journal, vol.154, no.1, February 2009.

[9] See also Mark Mazzetti and Thom Shanker, 'Russian Subs Patrolling off East Coast of US', The New York Times, 4 August 2009. Accessed 30 January 2011.

[10] Harding, 'Russian Subs stalk Trident in Echo of Cold War', op. cit.

[11] Then Minister of State for the Armed Forces the Rt Hon Bob Ainsworth MP announced that, while an eight-boat flotilla would be sufficient to meet predicted medium term tasks, ASTUTE's improved design, build, capability and availability would enable a further reduction to just seven boats by the time all ASTUTE boats are in service by 2022 (see Ainsworth: Response to a Parliamentary Question, in House of Commons Hansard Written Answers, Column 820W, 3 December 2007; House of Commons Hansard Written Answers, Column 55W, 10 December 2007).

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