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Unseen but vital: Britain and undersea security

European security has today an increasingly important maritime core. Such an observation might strike as surprising in the context of the single largest land conflict on the continent since the end of the Second World War. From this perspective, in February 2022, the launch of a new wave of large-scale Russian military operations against Ukraine – originally started with the illegal annexation of Crimea in 2014 – confirmed that state actors have replaced non-state organisations in mounting the primary challenge to the stability of the international order. 

Yet, while the fight to repel Russia’s territorial ambitions takes place in Ukraine, this war has also proved that a critical component of the centre of gravity of European economic security rests on the vulnerability of an invisible network of undersea connectors. More broadly, undersea spaces matter to Euro-Atlantic security, and not least to the United Kingdom (UK) as an insular nation. 

To articulate the significance of undersea security, this article, the first in a series more broadly related to aspects of undersea security and warfare, begins by exploring the maritime character of this century. The ocean today is an uninterrupted international highway linking the world together; its shipping lanes and networks of cables and pipelines fuel modern prosperity. As such, the ocean also stands as a primary target for revisionist regimes like Russia aiming to weaken and disrupt the maritime foundations of the international order and, as a result, to undermine the economic security of open economies. 

This characterisation of contemporary affairs is central to appreciate the multifaceted demands of European security – especially in times of war on the continent. In particular, because of the vulnerability of undersea infrastructure to state-sponsored military and paramilitary actions, undersea security is a matter which should be addressed as part of a national security effort. In the UK, the Royal Navy has the primary responsibility for tridimensional defence and security from threats to the maritime domain that risk undermining British national security. As such, it should convene efforts undertaken alongside other departments responsible for maritime security.

This leads to a related observation. The debate around undersea security in a maritime century is significant to the UK beyond matters related to the country’s own prosperity. Because of the centrality of undersea spaces to the broader economic stability of Europe, His Majesty’s (HM) Government has an opportunity to redefine its position as a substantive custodian of Euro-Atlantic security.

Subsea spaces in the maritime century

What is meant by ‘maritime century’? The answer is threefold. First, the ocean underwrites today’s physical and digital connectivity around the world, bringing countries closer together – not least in Europe. Second, it is a resource which demands concerted efforts to ensure its sustainable management, inviting responsible governance. Third, it is the largest staging platform for the projection of capabilities that empower states, or coalitions, with the choice to extend the use of force for the purpose of statecraft well beyond their borders. 

The first and third aspects of today’s maritime century have direct relevance to undersea security. Maritime connectivity is both a function of, and a key driver behind, contemporary prosperity. It is a well-known fact that some 90% of global trade is carried by sea, yet it is a less well-known fact that some 99% of the world’s communications are delivered by 1.4 million kilometres of submarine cables. Of no less significance, a substantial part of gas and electricity resources is delivered through a series of undersea connectors.

Map 1: Underwater cables in the Euro-Atlantic region

This complex web of energy and data highways has risen by such an extent that, every year, pipelines and cables provide nations the world over with access to products and services which – to use the words of Sir Stephen Lovegrove, the former UK National Security Advisor – ‘previous generations could only have imagined’. Crucially, the dependence between the maritime order and global prosperity is only likely to grow in the future.

Britain and undersea security

This is particularly true for the British Isles. In the UK, undersea energy pipelines and sea cables power the economic lifelines of the union, whilst seven international interconnectors define energy trade flows between the British Isles and Europe. In particular, between 2010 and 2021, the capacity of energy interconnectors has increased to unprecedented levels. According to official data, electricity imports to the UK increased almost tenfold, with HM Government planning to expand the country’s capacity from 7,440 megawatts to 18 gigawatts by 2030.

Within this context, France, Belgium, the Netherlands, Norway, and the Republic of Ireland are primary energy trade partners for the UK, with new interconnectors set to link the UK to Germany and Denmark in the near future. The undersea security of Northern Europe is indivisible from the security of the UK.

By a similar token, much of the UK economy and social services rest upon the continuous and uninterrupted use of undersea cables delivering data connectivity. As one informed observer recently noted, a disruption to the network of the approximately 60 British undersea cables would have potentially devastating consequences. Incredibly diverse aspects of life in the UK, from multimillion international bank transactions to medical activities resting on access to cloud-based access to data, would be at risk if a sufficient number of cables were severed or sabotaged.

The vulnerability of undersea cables and its impact on British security is not, however, an unknown question to the country’s political elites as it was first exposed by a groundbreaking report in 2017 authored by Rishi Sunak, now the Prime Minister. 

The above observations about undersea energy interconnectors and subsea cables highlight the security link between maritime connectivity and the third aspect of what defines today’s maritime century. The widening dependence of different countries on maritime connectivity has in fact expanded the strategic value for state actors to attempt to exploit its vulnerabilities to exert political pressure. In the past, fleets defined how states could use the sea to exert pressure on other actors. In the 21st century, the ability to deploy different capabilities to exploit the vulnerability of the networks on the ocean’s seabed has offered a new opportunity to expand the ways in which the concept of pressure from the sea can be pursued.

In the UK, undersea energy pipelines and sea cables power the economic lifelines of the union, whilst seven international interconnectors define energy trade flows between the British Isles and Europe.

In September 2022, the damage sustained by the Nord Stream pipelines linking Russia to Germany illustrated the vulnerability of the undersea component of today’s maritime order and the importance of its security. While the events have been subject to wild speculations, ongoing investigations have confirmed that explosives were used to damage the pipelines. Certain investigations have even suggested that a pro-Ukrainian group might have been involved in the damaging of the pipelines, though Russia remains the primary suspect in an attack which was seemingly aimed at undermining European resolve in providing support to Ukraine through threats to vital energy supply lines. Irrespective of who mounted the attack, it is clearer than ever that undersea pipelines are a growing target for those seeking specific political effects.

What is crucial in this incident is the emphasis it has put on how areas like the Baltic and the North seas contain very large networks of pipelines and cables that can be easily reached and, as a result, sabotaged. Relatedly, they raise interesting questions about how crucial nodes in the undersea energy and data connectors in other parts of the world link European security to theatres beyond its immediate continental boundaries.

Indeed, undersea cables are no less vulnerable. Submarine cables can be interfered with or cut, with significant economic losses, which can be exponentially more destructive for economies relying on single cables for their connective capacity. In 2017, a single cable was accidentally torn apart off the coast of Somalia by a ship’s anchor. The resulting Somali internet outage lasted approximately three weeks and it cost the country approximately US$10 million (£8.3 million) each day. On that occasion, the consequences were not purely economic, since the internet outage complicated efforts to combat a nationwide drought where half the population needed assistance.

In January 2022, an underwater volcanic eruption created similar devastating effects to life in Tonga, with the main cable being damaged resulting in a severe curtailing of internet activities for more than a month before services could be restored.

Threats to subsea infrastructure

While undersea infrastructure remains vulnerable to natural and accidental occurrences, other examples showcase more instrumental attempts at disruption. In October 2022, a UK-registered trawler was reported to have accidentally cut the main cable supplying internet services to the Shetland Islands. That the Russian scientific vessel Boris Petrov was present in the area at the same time raised questions about the plausibility of a Russian sabotage activity. When coupled with recent concern expressed by British flag officers over the substantial increase of Russian submarine activity in the vicinity of UK undersea cables, the risks to undersea security feel a real and challenging possibility.

In this regard, it is estimated that the Kremlin possesses the means and, crucially, the capacity, to exploit vulnerabilities in subsea infrastructure to advance its agenda. It can deploy different military, paramilitary, and non-military tools of statecraft to pressure or undermine other countries’ maritime connectivity and projection capacity. Russian authorities have modernised their capabilities and sought greater integration among land-based, cyber, and seagoing systems, from research vessels to unmanned underwater vehicles (UUVs), to cyber capabilities.

Significantly, the Kremlin is not alone in its attempt at exploiting undersea vulnerabilities; the People’s Republic of China and Iran have also been active in other parts of the world.

The undersea environment does not only matter to the UK because the British economy is so dependent on subsea infrastructure. It does not simply reflect a genuine need. It is also a powerful reminder that even a European terrestrial war, or the contest of wills among those involved in it, directly or in support of a given party, has multiple fronts.

Given the UK’s vital dependence on the stability of the undersea environment for its economy and sovereignty, engaging with the risks of its vulnerability is a strategic imperative. Yet, addressing the challenges presents also a unique opportunity to engage with a vital aspect of European security. It showcases the maritime character of regional security in a way that can coalesce together different European actors with shared vulnerabilities into cohesive action, whether through the North Atlantic Treaty Organisation (NATO), the Joint Expeditionary Force (JEF), or other European formats. 

Above all, undersea security is a manifestation of the multifaceted nature of contemporary geopolitics, even in the context of a major land conflict occurring in Europe. The undersea infrastructure that powers European prosperity is not just vulnerable to natural or man-made incidents. It is an inherent component of the national security conversation about core elements that need to be defended from the unwanted attention of revisionist state actors.


The undersea environment does not only matter to the UK because the British economy is so dependent on subsea infrastructure. It does not simply reflect a genuine need. It is also a powerful reminder that even a European terrestrial war, or the contest of wills among those involved in it, directly or in support of a given party, has multiple fronts. Revisionist challengers will opt for strategies where they can hurt their adversaries the most, while seeking to keep the costs and risks of their actions to a minimum. The undersea lifelines of modern prosperity are one such place where security can be tested, potentially jeopardising the British way of life.

Above all, Russia’s war against Ukraine is for a seapower state at the heart of the Euro-Atlantic world – the UK – not merely a challenge to national security. It also presents an opportunity. Upholding Europe’s security is about more than symmetric responses. Contributions through tanks and jets to Ukraine’s war effort may be essential, but they are only possible if the nation’s undersea surroundings are sufficiently secure to preserve the economy which sustains them. A land war does not make the requirement for a robust and capable navy – the Royal Navy – to secure undersea spaces irrelevant. On the contrary, it suggests two actions to consider. First, undersea security raises a question about a national maritime strategy in a competitive age, one in which integrating different departments’ actions has the potential to enhance national security as a whole. Second, for Britain, it also suggests that the path to national security and international relevance is about transforming national vulnerabilities into regional strengths.

Alessio Patalano is the Hebert Richmond Associate Fellow in Maritime Strategy at the Council on Geostrategy. He is also Professor of War and Strategy in East Asia in the Department of War Studies at King’s College London.

This article is the first part of a special series for Britain’s World on underwater warfare. The series is kindly sponsored by Dr Carl Stephen Patrick Hunter OBE.

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