Geopolitics of Baltic Subsea Infrastructure

The Baltic seabed is home to a web of subsea cables carrying vital telecommunications traffic between EU and NATO states, and linking Russia to its exclave, Kaliningrad. Vital data flows for the financial world, the internet and the military traverse the sea floor, which is also criss-crossed by power cables and gas pipelines. Consequently, the former ‘sea of peace’ has become a focal point of geostrategic rivalry in the wake of a sequence of attacks and disruptions to its critical infrastructure. Not unlike the Taiwan Strait, the Baltic is now a hotspot for geoeconomic and geostrategic competition. Its subsea cables – owned by a mix of European, Chinese and Russian entities – are largely maintained by US operators, reflecting the region's tangled strategic interests.

During the Cold War, the Baltic Sea was carved up by the Warsaw Pact and NATO. With Sweden and Finland joining the alliance, the small patch of sea has become a ‘NATO lake’ in the eyes of the Kremlin. Yet Russia is not the only ‘rival’ on the scene. Amid diplomatic rifts with Lithuania over the status of Taiwan, China’s relations with the Baltic states are fraught, with Estonia, Latvia and Lithuania having withdrawn from China’s 16+1 Central and Eastern Europe cooperation group. Damaging cables has been part of Beijing’s sub-threshold playbook in the South China Sea and beyond, an example of low-level aggression that forms part of a broader strategic approach using grey-zone tactics. Certain European officials have voiced concern about the Chinese ownership of cables in the Baltic region. Over the past decade, HMN Technologies, formerly Huawei Marine Networks, has emerged as the world’s fastest-growing builder and installer of subsea cables, giving China a significant, state-subsidized foothold in the global market, integral to its Digital Silk Road strategy.

In September 2022, the Nord Stream I & II pipeline explosion in the Baltic Sea was the initial wake-up call to Europe. While Russia was initially blamed by Western governments, other sources suggest it was the work of Ukraine or even the US. Revealing the acute vulnerability of the continent’s critical infrastructure, incidents of suspected sabotage have continued to pile up ever since. Although many cases involve accidental damage by commercial ship anchors – around 1,200 cables are damaged globally each year – distinguishing between sabotage and accident is increasingly difficult. The line between the two is further blurred by a convenient layer of plausible deniability for vessels and state actors alike, and a largely unenforceable regime of international maritime law.

The increasing frequency of damage to subsea communications cables in the exclusive economic zones of European countries has sounded many alarm bells. On 18 November 2024, the BCS East-West Interlink cable between Sweden and Lithuania was severed, with the Chinese tanker ship the Yi Peng 3 identified as the perpetrator. The same vessel was also linked to the cutting of the C-Lion1 data cable between Finland and Germany on 19 November. On Christmas Day 2024, Finnish authorities reported the severance of the Estlink 2 subsea power cable connecting Estonia and Finland, which caused short-term spikes in energy prices. It highlighted the potential for cascading economic impacts of disruptions. The latest cable damage, in January 2025 between Sweden and Latvia, led to the detention of the crew of the Bulgarian ship the Vezhen, responsible for the damage, who later denied all accusations.

In response to this series of incidents and in an atmosphere of heightened suspicion, Helsinki hosted an impromptu gathering of the heads of NATO states in January 2025 to address the protection of this critical infrastructure. Swedish Prime Minister Kristersson commented, ‘Sweden is not at war, but there is no peace either.’ This emphasizes the notion that the region is under attack in a grey zone of subsea proxy wars. Both NATO and the EU have been stepping up efforts to monitor and protect their infrastructure.

The Finnish NATO meeting led to the roll out of the UK-led Norden Warden initiative, which harnesses AI to detect suspicious activity by ships. The UK has also pioneered technology that listens to fibre optic cables to pick up reflections of any disruption. NATO has launched the ‘Baltic Sentry’, enhancing its military presence in the sea with aircraft, warships and drones. Meanwhile, the EU’s focus has been on boosting resilience against hybrid warfare. A ‘Cable Security Toolbox’, expected to be operational by the end of 2025, led by High Representative VP Kallas, the former Estonian prime minister, aims to tackle the challenges of protection, maintenance and deterrence. However, its effectiveness may be limited by fragmented accountability chains, as cable security remains primarily the responsibility of private actors.

Although not pointing the finger at Russia or China, the states that border the Baltic view the escalation of cable and pipeline attacks as part of the growing hybrid threat landscape. The power struggle and geostrategic competition played out below the water underscores a new geopolitical reality and shows that the future of sovereignty and national security extends to the bottom of the sea.