Exit ‘fourth battle of the Atlantic’, enter ‘Battle of the Bastions’: Part 1

The Memorandum | No. 47.2025

The case for a more forward approach

The United Kingdom (UK) is rediscovering its Cold War muscle memory. The return of peer competition has pushed the British Armed Forces to reforge their ‘warfighting’ readiness, following decades of underinvestment and a focus on counter-insurgency operations during the post-Cold War years. Russian air and naval capabilities once more pose a direct threat to the British Isles after a lengthy modernisation and rebuilding effort, which successive British governments have overlooked. In the words of Gen. Sir Gwyn Jenkins, First Sea Lord and Chief of Naval Staff: ‘the advantage that we have enjoyed in the Atlantic since the end of the Second World War is at risk’.

One of the key features of the future of the UK’s defence policy will be the creation of ‘Atlantic Bastion’, alongside Atlantic Shield and Atlantic Strike. This has led to a number of commentators to discuss the situation as the ‘fourth battle of the Atlantic’.

Atlantic Bastion was outlined in the Strategic Defence Review (SDR) as the Royal Navy’s ‘plan to secure the North Atlantic’ – primarily against underwater threats. The use of the word ‘Bastion’ harks to Soviet and subsequent Russian concepts, where defence of a Barents Sea Bastion is vital to defence of Russia and its strategic nuclear forces, and provides a safe haven for conventional strike platforms to threaten adversaries from.

In the coming decades, deterrence in the ‘Wider North’ will be decided by this ‘Battle of the Bastions’. Considering this, this two-part Memorandum aims to explore why the Barents Sea Bastion matters to the Kremlin, why the Atlantic Bastion matters to the UK, and why a more forward model of Atlantic Bastion is best suited to Britain’s needs, rather than a more defensive approach centred on defending the Atlantic at the Greenland-Iceland-UK (GIUK) gap.

The Russian Bastion

Although the Kola Peninsula is far from Russia’s economic heartland – which runs from St. Petersburg through Moscow to the Caspian Sea – it represents a vital piece of geopolitical real estate. The peninsula is one of the gateways to the Barents Sea, and is home to a number of key military bases. The Barents Sea itself is one of two preferred locations (the other being the Sea of Okhotsk) for Russian ballistic missile submarines to patrol.

These submarines give the Kremlin a powerful nuclear second-strike capability, and therefore options for escalation in the event of tensions or during conflict. The bases also host a suite of Russian missile launch platforms, including submarines, surface ships, aircraft and land-based platforms which could launch waves of long-range strike weapons towards Britain and its allies.

Another reason – one which is a new development – is the impact of climate change. Russia has long relied heavily on its ports for trade, particularly the export of resources such as wheat and oil. Without these revenues, the regime of Vladimir Putin, President of Russia, would struggle to function, let alone sustain aggressive action. In an Article Five situation, the North Atlantic Treaty Organisation’s (NATO) ability, in extremis, to shut off shipping completely to Russian ports in the Baltic and Black seas is a powerful deterrent.

The potential opening up of the Northern Sea Route threatens to undermine this. It is no coincidence that despite the fact much of Russia’s defence expenditure has been reprioritised towards the war effort against Ukraine, one of the few areas which continues to receive funding is the modernisation of the Northern Fleet and the expansion of Arctic bases.

Atlantic Bastion

There are similar reasons why Atlantic Bastion is of great importance to Britain, and more widely to NATO. Defence of the UK’s nuclear deterrence and the Home Islands necessitates keeping Russian launch platforms out of the Norwegian Sea. Given the nature of cost-saving measures in defence, and of wider efficiency driving efforts in the civil economy, most of Britain’s key military and civil sites which would be vital to sustaining a war effort – such as ports, power generators, air bases and defence-industrial hubs – are few in number and concentrated in disposition.

Further to this is the importance of transatlantic ‘Sea Lines of Communication’ (SLOCs). Regardless of the likelihood of American reinforcements and materiel coming across to Europe, the continued movement of goods beyond the GIUK gap will be crucial to keeping Europe (including the UK) functioning in a crisis; especially the continued import of materials needed to sustain the defence-industrial base. Yet, this is also true of the North Sea, which SLOCs to reinforce the Baltic states and Scandinavia must cross. Defence of the GIUK gap protects the former, but leaves the latter exposed – whereas a more forward defence posture shields both.

Echoes of the past

This new era of contestation has many echoes to the Cold War. In fact, the period between 2020-2035 has thus far, and will likely continue to have, a number of similarities to the situation faced by NATO planners in the period spanning roughly 1975-1990. There are obviously a number of major differences, including geopolitical and technological developments, but lessons can nonetheless be drawn.

For a start, Russia has vastly expanded its capabilities in recent years in the maritime domain, and has caught NATO napping. Following the post-Soviet collapse, the Russian Navy has undergone an impressive modernisation programme, including a suite of new nuclear attack and ballistic missile submarines, as well as surface combatants armed with large numbers of long-range missiles. European countries allowed their own naval power to atrophy in the 1990s and 2000s, and with a focus on low-intensity operations, many NATO warships are ill-suited to the demands of peer naval conflict. The inability of most European warships to deploy to the Red Sea to defend against the Houthis, a rebel group in one of the world’s poorest nations, is testament to this.

Although some European countries are rebuilding their naval forces, this is not going far enough or fast enough. This is not a dissimilar situation to NATO’s initially slow reaction to the Soviet naval buildup of the 1970s under Adm. Sergey Gorshkov. At the start of Ronald Reagan’s first term as President of the United States (US), John Lehman, Secretary of the US Navy (1981-1987), initiated a substantial naval build up programme. Lehman’s words from then now ring true once more: ‘clear maritime superiority must be reacquired’.

There are also lessons in NATO’s switch from a posture more focused on SLOC defence in the 1970s to a more assertive forward maritime strategy allowing power projection. However, one key difference will be that given the demands which could be placed on American air and naval forces in the event of a two-front crisis, European militaries will have to secure Atlantic Bastion under the assumption of minimal support from the US.

The contested zone, a very active ‘no man’s land’

Another key difference in the 21st century is that the decisions of Finland and Sweden to join NATO have fundamentally changed the geopolitics of the Wider North. This change presents a perfect opportunity for the UK to leverage its allies and assert a more forward vision of Atlantic Bastion, with the First Sea Lord’s announcement of Atlantic Strike being a very welcome step in this direction.

Given the nature of Anti-Access/Area Denial (A2/AD) approaches, there will be a swathe of the Wider North covered by the systems of both the Russian and British bastions. This will see a struggle for the ability to sustain and operate forces within this contested zone, while at the same time protecting one’s own deep areas and simultaneously trying to strike into the adversary’s deep areas. Over time, the goal would be to have the ability to keep one’s own bastion as firm as possible, degrading the adversary’s bastion over time, and slowly moving the contested zone further into enemy territory. Dismantling Russia’s bastion in a matter of days, as Israel was able to do to Iranian air defences in June 2025, is unlikely, but the aim should nonetheless be to degrade it as rapidly – and as cost-effectively – as possible. In this sense, defensive systems are not there to protect a nation ad infinitum, but rather to buy time for offensive action to do its job.

The focus of Atlantic Bastion, therefore, should be pushed eastward. The GIUK gap is insufficient. This mindset reflects ‘fourth battle of the Atlantic’ thinking – of securing American reinforcements across the Atlantic – but Russian submarines are well within range of the UK before that point is reached, and could disrupt equally important SLOCs across the North Sea. Instead, Britain should seek to incorporate Norway, Sweden and Finland closer into its bastion, and aim for its ‘net’ to be cast from the Norwegian coast to Svalbard to cover what is known as the ‘Bear Gap’. From here, the UK can seek to project power into the contested zone in support of its allies.

Such a ‘more forward’ approach would be of course more demanding. The environment of the Wider North is unforgiving; the wear and tear on people and equipment is immense. This has implications for problem-setting for the capabilities which Britain seeks – as well as which capabilities are high priority in the first place – and the challenge of integration, not just within the British Armed Forces, but with regional allies too. These themes are explored in greater detail in Part 2 of this Memorandum.

William Freer is a Research Fellow in National Security at the Council on Geostrategy and an Associate Fellow at the Royal Navy Strategic Studies Centre.

---

To stay up to date with Britain’s World, please subscribe or pledge your support!

What do you think about this Memorandum? Why not leave a comment below?