The Fragile Web on the Ocean Floor
Between 95 and 99 percent of global internet traffic travels along a vulnerable, squiggly network of subsea cables that crisscross the ocean floor like a spider’s web, resting largely unprotected at the bottom of the sea. This fragile infrastructure forms the hidden backbone of modern communication and energy, yet public awareness of its vulnerability remains remarkably low. While the public often conceptualizes data storage as residing harmlessly in the cloud, the physical reality relies on undersea cables that have expanded rapidly since Queen Victoria dispatched the world’s first transoceanic message in 1858.
The End of Cold War Safety
During the Cold War, these vital links remained largely unmolested even at the height of geopolitical tensions. Today, however, that era of safety has vanished. Security analyst and Foreign Policy columnist Elisabeth Braw explores this escalating crisis in her new book, Undersea War: The Battle to Control the Cables and Pipelines That Connect Our World. The book opens in November 2025 with then-U.K. Defense Secretary John Healey publicly exposing a direct confrontation between British armed forces and the Yantar, a Russian Navy subsurface vessel known for frequenting Western European waters. While intelligence services have long tracked spy ships, the modern threat involves these vessels being utilized to deliberately sever cables.
Shadow Fleets and Open Ocean Loopholes
Malicious actors increasingly rely on merchant vessels operating under flags of convenience to mask their activities. Intelligence estimates indicate that Russia is currently deploying a shadow fleet of at least 600 ships. Many of these are merchant vessels using flags of convenience. While primarily utilized to transport oil in direct defiance of international sanctions, these vessels are frequently repurposed for intelligence gathering, communications interference, and dragging anchors across the seabed to slash critical infrastructure.
Because these incidents frequently unfold beyond the 12-nautical-mile limit of territorial waters—where coastal state laws no longer apply—policing the open ocean remains exceptionally difficult. Perpetrators caught in the act can simply claim mechanical failure or pretend they were unaware their anchors had dragged for extended periods.
Real-World Disruptions from Matsu to Europe
The vulnerability of subsea infrastructure is not merely theoretical. The cascading impact of a severed line was starkly demonstrated on February 8, 2023, when an underwater cable connecting Taiwan to the Matsu Islands was abruptly snapped. Daily life on the archipelago came to a complete standstill for its 13,000 residents. Information became restricted to word of mouth, touch screens were rendered useless, and digital payment systems failed entirely.
Similar disruptions have plagued European waters, with incidents involving the Balticconnector, Nord Stream, C-Lion1, and Arelion and Elisa cables. Meanwhile, great power competition is expanding into new frontiers.
The Fluid Transition Between Peace and War
Addressing the NATO summit in June 2025, German Chancellor Friedrich Merz captured the new paradigm when a reporter asked how leaders could distinguish a mere provocation from an act of war. Merz replied that daily attacks on data networks and the destruction of submarine cables signify a fluid transition between peace and war rather than a digital zero or one. As Braw concludes in her book, defenders in this new reality are operating without manuals because none yet exist.
