The recently published, long-awaited British Strategic Defence Review (SDR) reasserts commitments to NATO and the Euro-Atlantic theatre. It is the maritime sphere, however, that emerges as the primary focus and beneficiary.This is evident in the striking, headline-grabbing target of building ‘up to’ 12 new nuclear attack submarines (SSNs), continuing commitment to two large aircraft carriers, and emphasis on a substantial ongoing surface shipbuilding programme. The SDR also reflects an underlying assumption that Britain’s strategic priorities are now defence of the homeland, its vital communications and offshore tapestry, alongside a NATO contribution focused on a seaborne nuclear deterrent and Eastern Atlantic security. By contrast, the commitment of British land forces on the continent seems set to be more limited and specialised.

This maritime focus is also apparent in the emphasis the SDR gives to ‘Atlantic Bastion’, the Royal Navy’s plan, also known as Project Cabot, ‘to secure the North Atlantic for the UK and NATO against the persistent and growing underwater threat from a modernising Russian submarine force’.  The SDR is enthused by the opportunity to collaborate with multiple government, NATO and commercial partners to exploit advanced new anti-submarine (ASW) warships and maritime patrol aircraft, together with air, surface and submarine drones, to provide a networked detection and targeting system using the latest sensors and artificial intelligence (AI) techniques. The proposed ‘Bastion’ would eventually cover a box from the coasts of Western Europe out to the longitude of eastern Greenland and from the Arctic ice shelf to the latitude of Lisbon.  It is a rare example in the SDR of a desired outcome as opposed to actual capability.

Viewed in the glossy SDR brochure, this all looks compelling, but what are the underlying realities driving this concept? Essentially, ‘Bastion’ will regenerate and extend techniques to detect, track and ‘kill’ hostile submarines developed during the Cold War, beginning with the sophisticated US Navy SOSUS seabed listening arrays to which Britain enjoyed access. By the mid-1980s, SOSUS was evolving into a wider surveillance network using shipborne mobile arrays (some British) and new satellite sensors. Four decades on, elements of this network remain, but resources devoted to it have declined, reducing its scope against potential Russian threats, while continued American commitment in the Eastern Atlantic area is in doubt.

The SDR does not define the ‘growing’ Russian submarine threat that justifies ‘Bastion’. The Russian Northern Fleet submarine force responsible for the Atlantic theatre, although far smaller than Cold War days, remains substantial on paper. It comprises about 16 SSNs, seven nuclear ballistic missile boats (SSBNs), and a handful of conventional boats and more specialist vessels. However, much of this force is 30 years old and of doubtful effectiveness. By the early 2030s, despite new commissioning, the size and quality will be close to planned Royal Navy submarine strength across that decade. Certainly, the Russian Atlantic SSN force will become inferior to combined British and French numbers. Furthermore, Russia’s own recently announced ‘new naval strategy’ suggests its overall planned submarine output up to as far as 2050 remains modest.

Nevertheless, the prospect of a smaller Russian force does not permit complacency. Although their SSNs will be too few to pose the same risk they did during the Cold War – either to Western SSBNs now with vast space southward in which to hide, or to transatlantic shipping – other threats are becoming more complex, dangerous and difficult to manage.

Most of the Russian SSBN force would probably deploy under the shelter of the Arctic ice, with their SSNs providing a protective screen against NATO attackers. The SSNs, however, could also move south of the Greenland–Iceland–Faeroes–Shetlands Gaps to fire ‘bolt from the blue’ hypersonic missile volleys at short range against key NATO strategic assets, or to launch innovative drone attacks against vital underwater infrastructure.

Russia has also heavily publicised the imminent arrival of its Poseidon nuclear-propelled, nuclear-armed, long-range underwater drone, which is aimed at coastal cities and other accessible targets. Launched from its own specialist submarine carriers and decades in development – primarily to hedge against a Western breakthrough in anti-ballistic missile defence – Poseidon’s military utility and viability are questionable, but as a coercive terror weapon it is powerful.

Given these threats, the case for regenerating a comprehensive system to detect, identify and track Russian submarine movements and, in wartime, facilitate their destruction, is strong. The SDR identifies this as a primary British NATO task, although it does not clarify allied participation. It is possible the US Navy may no longer commit significant ASW resources east of Greenland, but other NATO partners, notably Norway, Denmark, Holland, France and Germany could support a British initiative, albeit in different ways.

So, what might ‘Atlantic Bastion’ look like from its provisional planned start date of 2030?  Its British core rests on three elements: the new Type 26 global combat ship being introduced from 2028; SSNs; and maritime patrol aircraft. All will be in short supply. The Type 26 promises to be an outstanding ASW vessel, but is expensive with only eight vessels planned, allowing one permanently on station from 2030 and two by mid-decade. At current build-rates, none of the promised 12 new AUKUS SSNs will be operational before 2040 and the need to replace the current Astute Class means no growth in force before the end of that decade, neatly illustrating the gap between political presentation and practical implementation.

Assuming current problems in supporting the seven Astute-class submarines are solved, it will be hard to devote more than two consistently to ‘Bastion’. Meanwhile, the Royal Air Force has just nine P8s: excellent state-of-the-art maritime patrol aircraft, but barely a quarter of Cold War strength, although the SDR suggests supplementing them with some of the 16 long-range Protector drones just coming into service.

While the brutal reality of these numbers constrains British ambition to monitor the vast ‘Bastion’ area, two factors make the picture more positive. First, the NATO partners mentioned above could comfortably double the platforms on station and add a significant force of conventional submarines, which would be particularly effective if deployed in the ‘Gaps’. It helps that many partners also operate P8s, while Canada is building Type 26s and Norway may follow, considerably enhancing interoperability.

Second, there is the SDR endorsement for exploiting drones, digitally networked sensors and AI to achieve a major capability multiplier effect. Essentially, drones become self-propelled towed arrays, with sheer numbers deployed compensating for their minimal mobility. In time, they could be fitted with weapons, thus inhibiting hostile access in select areas like the ‘Gaps’, a modern version of the traditional minefield. British prototypes for surface and underwater ASW drones, potentially suitable for ‘Bastion’ deployment, are undergoing trials and the Type 26 has been optimised for drone control and support, although more specialist ‘mother ships’ will probably be needed.

Together with industry partners, translating a theoretical vision with myriad parts over the next five years into an effective operational system, able to operate reliably in the demanding North Atlantic environment, will be hugely challenging and demand significant investment from a stretched defence budget. Given requisite leadership, drive, funding and support from Allies, it should be just about possible.