UK’s Astute Fleet

The readiness of the UK’s fleet of nuclear attack submarines (SSNs) has been a source of enduring concern over the previous half decade. With five Astute-class SSNs currently in service (less than half of what the UK had at the end of the Cold War), the Royal Navy fields fewer submarines than has been the case at any given time in recent history. Moreover, challenges with respect to maintenance, compounded by the priority accorded to ensuring that the UK’s continuous at sea deterrent remains operational, have resulted in periods during which the UK did not have an attack submarine at sea. In light of the growing threat posed by Russia’s Northern Fleet, ensuring the readiness of a capability which remains a key UK offer to NATO as an alliance member will be critical.

The Balance of Forces

The competition to maintain a commanding position in the undersea operating environment played a crucial role in the Cold War. During the early years of the Cold War, tracking Soviet SSNs as they attempted to break through the Greenland–Iceland–UK gap was vital to Allied efforts to ensure that US reinforcements could cross the Atlantic. In the 1980s, NATO’s approach shifted. In the context of a forward maritime strategy, the ability of NATO to menace Soviet ballistic missile submarines (SSBNs) in their bastions was a key component of deterrence against the USSR, which was presumed to enjoy considerable advantages in Central Europe. The success of this approach was perhaps best illustrated by the fact that by the end of the Cold War, the commander of the Soviet Northern Fleet was compelled to request a trebling of his budget if the maritime component of Russia’s nuclear triad was to be adequately protected.

Since the end of the Cold War, there has been a rough symmetry in how Allied and Russian forces have evolved, with both sides undergoing quantitative reductions but qualitative improvements. The Russian Northern Fleet fields 13 active SSNs and guided missile submarines (SSGNs), a far cry from its heyday, but vessels such as the Yasen and improved Akula II and III are considerably quieter than their predecessors. Allied submarine fleets including the Royal Navy’s submarine flotilla have endured a comparable drop in capacity, with the Royal Navy fielding fewer than half as many submarines as it did in 1990, although the Astute is also considerably quieter and more capable than the Trafalgar class.

The major shift, however, is that the US SSN fleet will increasingly be focused on demands in the Indo-Pacific, where robust Chinese anti-access/area denial capabilities will put surface vessels at ever greater risk, but where US submarines still enjoy considerable advantages over the People’s Liberation Army Navy’s noisy SSNs and immature anti-submarine warfare assets. As the size of the US submarine fleet (which is already well short of the 66 boats the US navy requires to meet its commitments) shrinks during the late 2020s and reaches a low of 46 boats by 2030, it is not unlikely that the Pacific, where 60% of US submarines are typically deployed, will receive an ever larger portion of a temporarily smaller SSN fleet. Past 2026, the US navy expects to increase its build rate to three attack submarines per year, which should see it return to and then exceed its current strength by 2035, although the real effects of this regeneration of capability (if achieved) will be somewhat attenuated by the fact that the Chinese threat will not stand still.

In Europe, this raises the possibility of short-term capability gaps emerging. In this context, the readiness of the Royal Navy’s submarines – which are, among other things, the only non-US Allied nuclear submarines that regularly perform under-ice operations – is both a national and an Alliance-level concern.

With five Astute-class SSNs currently in service, the Royal Navy fields fewer submarines than has been the case at any given time in recent history

It would be a mistake to assume that the Russian submarine fleet is ten feet tall. Of the 13 SSNs and SSGNs currently fielded by Russia’s Northern Fleet, only a handful can be described as truly modern. While the Russian Yasen and Yasen-M are competitive against Western submarines, four of the Northern Fleet’s SSNs are aged Sierra II and Victor III-class boats, and the fleet also fields two older (though still credible) Oscar-class SSGNs. The fleet’s Project 971M/I Akula-class submarines are slowly returning to readiness after a trough in capability during the last decade, with SSNs such as the K-328 Leopard and K-154 Tigr completing refits in the early 2020s. Even so, the number of project-improved Akulas at the fleet’s disposal in the next several years should hover around six, meaning that the fleet currently fields eight SSNs/SSGNs (six Akulas and two Yasen/Yasen-M) that are credible in a modern context. Although Russian practice has historically prioritised surge capacity over presence at sea (which is why the Soviet Navy only deployed 25% of its SSNs at any given time during the Cold War as opposed to the 66% which the US navy maintained), a very high readiness rate of 80% would imply six or so modern SSNs being available in Russia’s Northern Fleet in a crisis (though submarines could be moved to the north from the Pacific Fleet).

Russia will field more Yasen-class SSGNs by the end of this decade. While the lead boat of the class, the Severodvinsk, took 15 years to build, its successor the Kazan was constructed in eight years and accepted into service after 12, while the third and fourth submarines in the class (both allocated to the Pacific fleet) reached full operational capability in eight and nine years respectively. Two more boats were ordered in the first tranche of Yasen-class submarines to be built, and will likely enter service in 2024–25. In this period, the Northern Fleet’s complement of Yasen-class boats will increase from two to three (with three Yasen-class boats in the Northern and Pacific Fleets respectively). The Russian navy has commissioned a further six boats in the class which will likely enter service in the 2030s, assuming a comparable build rate. At present, there is some indication that the Yasen fleet appears to have been committed to the maintenance of a near year-round presence off the coast of the continental US – something which will likely require all four of the boats currently in service to maintain, and which will leave the fleet with limited surge capacity. One reason for this might be that the Russians are replicating the Soviet policy of delivering an “analogous response” to US missile deployments in Europe (which will occur from 2026 onwards) through the deployment of missile-equipped submarines to the Western Hemisphere. If this is the case, the ability of the Yasen fleet to surge multiple SSNs into the Atlantic will be limited until the early 2030s.

The first part of the 2030s, then, will represent a point of particular concern as a nadir in US capability coincides with the growth of the Yasen SSGN fleet as a consequence of investments being made now. Past the mid-2030s, both a recovery in US numbers and progress on SSN (R)/SSN AUKUS will (in the absence of delays) result in the rectification of this imbalance. While the situation in the Atlantic is not presently critical, it is vital that steps are taken to ensure that a window of vulnerability does not open in the 2030s.

Getting More Out of Astute

It should be assumed that some of the issues plaguing the Royal Navy’s submarine readiness right now can be resolved at the speed of relevance if the threat is likely to become most acute at the end of the decade. To use one example, the lack of available docks at Devonport (which has forced a prioritisation of SSBN maintenance) should be resolved in the coming years, as 10 Dock at Devonport becomes available and 15 Dock is converted to service the Astute class. Furthermore, the floating docks being procured under the Additional Fleet Time Docking Capability (AFTDC) programme should help with the issue of readiness, although this programme is nascent and no date has been set yet for the tender. Finally, the Astute fleet will grow by two SSNs during the next few years. While still considerably smaller than the Russian Northern Fleet in numerical terms, the Royal Navy can, in conjunction with other European SSN operators such as the Marine Nationale, offset the effects of a relative reduction in US capacity and match a notional Russian force of 10–11 modern attack submarines which may be operated by the Northern Fleet in the early 2030s.

This is by no means a certainty, however, and the fate of programmes such as the AFTDC remains to be seen. Moreover, infrastructure investments will not entirely resolve some of the challenges highlighted by Deputy Chief of the Defence Staff Lieutenant General Rob Magowan, which include supply chain management and the availability of engineers.

Furthermore, the question of availability will only be exacerbated by the rotational deployment of an Astute-class submarine to Perth beginning in 2027. To be sure, AUKUS is not necessarily a drag on capacity – investments in the UK’s submarine industrial base by Australia may be an important part of the solution to certain issues such as supply chain management. However, the timing of the rotational deployment bears considering, since this could coincide with the point at which the Russian submarine threat peaks. There may be competitive advantages to be gained in Europe from the deployment of submarines to the Pacific. To the extent that Russia (incorrectly) assesses AUKUS to be a full-fledged military alliance, it is likely to view any steps to delivering on it as a threat to the Russian Far East where, notably, half of the incoming batch of Yasen-class SSGNs will be based. As such, the strategic ambiguity of a rotational presence could play a role in fixing Russian assets away from Europe.

These opportunities notwithstanding, a more salient question for the Royal Navy may be the timing and form that its rotational commitment to Submarine Rotational Force West takes. One approach to how the rotational deployment might be conducted by partner states could conform to the logic of dynamic force employment articulated by former Secretary of Defence James Mattis, in which forces were expected to make short, irregular deployments geared towards an emphasis on readiness and operational uncertainty. If the deployment schedule of British and US SSNs was made shorter and larger in scale (with multiple SSNs on any deployment but for a shorter period), this could impose a degree of operational uncertainty on Russia while maintaining a regular drumbeat of visits to Australia for functions such as training and political signalling.

Alternatively, if a likely multi-year rotational forward presence is deemed politically vital to the success of AUKUS, the UK would do well to deliver its part of the commitment before 2030, which is when the threat in Europe will peak.

The period from 2025–35 will likely be one of maximal concern as the demand from the Indo-Pacific and a qualitative increase in the Russian threat converge

In addition to thinking about how longer-term commitments are managed and sequenced, the tasking of the Astute fleet could become more focused. For example, the role of SSNs as Tomahawk land attack missile (TLAM) launchers in support of expeditionary activity might reasonably be sacrificed given that this entails the use of a highly specialised platform for functions that can eventually be played by surface vessels, and draws on capacity in support of relatively peripheral missions. Until the Type 26 enters service, readiness for the contingent employment of limited stocks of TLAM outside Europe might be treated as a task to be effectively gapped.

In a similar vein, a greater emphasis might be placed on committing more resources to key activities such as ASW and exercises such as Ice Exercise, in which the Royal Navy and US Navy practice under-ice SSN operations (something no European partner other than the UK provide the US), even if this comes at the expense of other standing commitments (beyond nondiscretionary missions like protecting the deterrent). A more narrowly focused pattern of activity could help optimise a limited fleet for its core functions, which during the latter part of this decade and the first part of the next could in turn set the conditions for a more balanced pattern of activity towards the middle of the next decade and beyond.

Third, the relative balance between the submarines of the Russian Northern Fleet and Allied capabilities can be influenced in certain ways. As mentioned, the rotational deployment of Yasen-class submarines in what appears to be an analogous response posture will rob Russia of surge capacity. Similar long-distance deployments as part of an analogous response approach might be incentivised by forward operations in the Barents Sea (which former commander of the Russian Navy Admiral Yevmenov discussed with some concern in the journal Morskoi Sbornik), or through live exercises simulating the firing of submarine-launched cruise missiles from forward positions (something which is viewed as a matter of concern since British missiles are viewed as a component of a much larger US prompt strike capability). These represent notional examples rather than concrete solutions, but the broader point is that the pattern of activity the submarine service should aim for is one in which short bursts of Allied activity stimulate much longer Russian deployments. While the number of hulls in the Russian Northern Fleet cannot be impacted, the number available to Russia at any time can be.

Conclusion

Ultimately, there are no simple fixes to the challenges that shortfalls in SSN numbers will pose. These shortfalls will not be acute until later in this decade, by which time the UK should have overcome some of its own short-term challenges. The period from 2025–35 will likely be one of maximal concern as the demand from the Indo-Pacific and a qualitative increase in the Russian threat converge. In this window, it will likely be vital to narrow the number of tasks performed by the Astute fleet as much as possible. Beyond this point, there will be greater room for the fleet to support longer-term goals, including those entailed under AUKUS.

Sidharth Kaushal is Research Fellow for Sea Power at RUSI. His research at RUSI covers the impact of technology on maritime doctrine in the 21st century, and the role of sea power in a state’s grand strategy.