Connecting the Ends: A Baltic–Indo-Pacific Agenda for Undersea Infrastructure Security

Critical undersea infrastructure — including communications cables, electricity interconnectors, gas pipelines, landing stations, and associated control systems — forms a largely invisible but indispensable foundation of modern societies.

It supports international data traffic, financial markets, cloud services, military communications, and cross-border energy exchange. Although located on the seabed, disruption can rapidly affect the economy, public administration, internal security, and national defence.

This report shows that these systems are vulnerable because they span long distances, traverse congested maritime areas, and lie within overlapping legal jurisdictions. Much of the infrastructure was designed primarily to withstand natural hazards, technical failures, and accidental anchor damage rather than deliberate sabotage or state-directed hybrid activity. Recent incidents in the Baltic Sea and around Taiwan demonstrate that damage to cables and pipelines can no longer be treated solely as a technical or maritime-safety issue. The undersea domain has become part of wider strategic competition involving Russia, China, and western and Indo-Pacific partners. 

Russia and China differ in their objectives and methods, but both exploit the dual-use character and limited visibility of the maritime domain. Russia’s activity is closely associated with grey-zone pressure, including infrastructure mapping, response testing, legal probing, the use of civilian vessels, and the preservation of options for disruption during a future crisis. China’s approach is more closely connected to its ambitions as a maritime power, its global survey activities, technological development, military planning, and efforts to shape maritime governance. In both cases, the central challenge is attribution: the same physical damage may result from an accident, negligence, or a deliberate act, while proving intent remains difficult. 

This report concludes that complete physical protection of every cable and pipeline is neither technically nor economically realistic. The more effective approach is layered and resilience-based. It combines early warning, integrated maritime and undersea situational awareness, redundancy, rapid repair, public-private cooperation, clear legal responsibilities, and societal preparedness for prolonged disruption. Resilience is also a form of deterrence by denial: if services can be maintained, traffic rerouted, evidence collected, and damaged infrastructure quickly restored, sabotage yields less political, economic, or military benefit. Some of the recommendations arising from the report are as follows: 

• Establish a permanent Baltic-Indo-Pacific dialogue that brings together governments, navies, coast guards, intelligence services, regulators, operators, researchers, and technology companies to develop a shared threat picture and exchange lessons from incidents. 

• Integrate Automatic Identification System (AIS), radar, satellite, sonar, operator, and intelligence data to detect anomalous vessel behaviour near critical infrastructure, including unexplained course changes, anchor dragging, AIS manipulation, repeated presence, opaque ownership, and unusual survey activity. 

• Harmonise maritime-forensics standards, evidence-sharing procedures, investigative teams, and rules for inspecting suspicious vessels so that cases do not become trapped in jurisdictional gaps. 

• Create regional strategic repair arrangements covering vessels, crews, spare parts, cable modules, prioritisation, and joint funding, while linking Japan’s industrial capabilities with European and regional mechanisms.  

• Conduct regular multi-agency exercises and strengthen societal preparedness, strategic communication, and the integration of physical, cyber, space, information, and electromagnetic protection. 

• Develop a practical Japan-Estonia and wider Baltic-Indo-Pacific resilience network focused on technology, maritime domain awareness, repair capacity, legal cooperation, and rapid transfer of lessons between regions. 

See also: ICDS Webinar: Critical Underwater Infrastructure Security and Protection in Japan and in the Nordic-Baltic Region

Views expressed in ICDS publications are those of the author(s).