The modern digital economy rests on a foundation that is remarkably thin, deeply hidden, and increasingly vulnerable. Across the globe, an estimated 1.5 million kilometers of subsea communications cables power international telecommunications, internet traffic, and global financial systems. Comprising over 600 in-service cable systems, this critical infrastructure operates largely out of sight on the ocean floor. Yet, as geopolitical tensions mount, maritime traffic intensifies, and a wave of critical infrastructure ages out of service, experts warn that the resilience of the world’s submarine cable network is facing unprecedented stress.
Nowhere is this vulnerability more apparent than in archipelagos and narrow straits worldwide. Consider the Matsu Islands, an archipelago of 36 islands in the East China Sea situated just off the southeastern coast of mainland China. Administered by Taiwan since 1949 alongside the Kinmen and Penghu Islands in the Taiwan Strait, the Matsu Islands rely on vital undersea connections to Taiwan’s main island. These include the Taima No.2 and Taima No.3 submarine cables, with a fourth, Taima No.4, soon to join them.
Because the Taiwan Strait is a shallow body of water with an average depth of just 70 meters, cables resting on its seafloor are perpetually exposed to ship-based activity, such as fishing equipment and heavy anchors. These particular links have suffered a staggering run of misfortune: between 2018 and 2022, cables connecting Taiwan to the Matsu Islands were severed 27 times, followed by four major outages between 2023 and 2025.
Similar vulnerabilities plague other shallow bodies of water, such as the Baltic Sea. Home to roughly a dozen submarine communication cables alongside undersea electricity and gas pipelines, the Baltic Sea has recorded 11 disruptions to its subsea systems since 2023.
These localized failures highlight a much broader global reality. Submarine communication cables are indispensable to international connectivity. If widespread disruptions were to occur, existing satellite systems simply possess neither the capacity nor the bandwidth to replace them. In such a catastrophic scenario, entire communities could find themselves completely isolated, triggering severe logistical and economic ramifications.
Protecting the Cable
Classified as critical infrastructure, submarine cable systems are engineered to withstand a variety of environmental and accidental hazards. However, the modern geopolitical landscape has introduced deliberate disruption to a list of risks that historically included only geological shifts and maritime accidents.
The strategic value of severing undersea telegraph and communication lines is far from new. On the night of August 4, 1914—just days after Britain declared war against Germany—the British cable ship HMTS Alert sailed from Dover into the English Channel. Trailing grappling hooks along the seabed, the vessel hauled up five German transatlantic and European telegraph cables and cut them. The operation severed Germany’s direct, secure submarine links to the Americas, Africa, Spain, and the rest of Europe. Consequently, Berlin was forced to rely on wireless radio transmissions, which British intelligence readily intercepted and decrypted, famously capturing critical messages such as the Zimmermann Telegram. This exact tactic of deliberately severing undersea cables was repeated by the British in September 1939 to cut German lines to Lisbon and New York.
Today, modern subsea cables face a myriad of threats operating on the ocean floor. To defend against these risks, the inner core of fiber-optic strands and its copper conductor sheath can be wrapped in layers of steel wire jacketing, creating armored segments primarily designed to reduce vulnerability to shipping accidents.
However, cross-sectional diagrams of armored cables can be misleading. Armoring is typically applied only to the segments leading to shallow coastal waters and surface landing stations. The vast majority of deep-sea cable segments use only internal components: optical fibers and a single thin steel thread wrapped in silicone gel, surrounded by a copper sheath used to power repeaters, all enclosed in polyethylene. These deep-sea segments lack external armor entirely and measure roughly 20 millimeters in diameter—about the size of a standard garden hose.
These lines eventually surface at cable landing stations, which are typically secure, plain facilities equipped with reliable power sources. Planners prefer coastal locations featuring low volumes of maritime traffic and steep drops to the deep-sea floor, minimizing the vulnerable distance coastal ships must navigate near the cable. Many jurisdictions also establish official Cable Protection Zones, warning vessel operators to refrain from anchoring and fishing in designated areas.
Cable Routing
Achieving optimal resilience through cable routing involves balancing multiple competing objectives. Route planners strive to keep cable paths as short as possible to control capital expenditures and minimize end-to-end signal delay. At the same time, routes should ideally avoid active geological zones, such as tectonic plate boundaries and mid-plate rifts.
While placing cables at extreme ocean depths protects them from surface shipping and hostile interference, it simultaneously complicates localization and repair operations when faults do occur. Furthermore, geography often forces numerous systems through narrow maritime choke points.
The Bab al-Mandab Strait, for instance, serves as a vital conduit not only for surface vessels passing between the Indian Ocean and the Red Sea, but also for 16 submarine cables. In September 2025, several cables were severed in the strait, disrupting an estimated 25 percent of total capacity connecting Asia, Europe, and the Middle East. Waters controlled by Houthi forces remain effectively ungovernable for cable protection efforts.
Similarly, the Singapore Strait accommodates 35 cable systems in shallow waters marked by heavy maritime traffic. Further north, the Luzon Strait between Taiwan and the Philippines hosts 18 cables. In December 2006, an earthquake triggered submarine landslides in the Luzon Strait that severed every cable running through the passage and buried many under deep sediment, requiring 11 repair vessels 49 days to restore full service.
Geopolitics further dictates routing strategies. Cable owners consistently avoid politically unstable territorial waters whenever viable alternatives exist. Regulatory frameworks, such as those enforced by the United States Federal Communications Commission (FCC), place strict constraints on cable landings, prohibiting equipment or services from companies deemed national security threats and blocking landings that connect to designated foreign adversaries.
While land routes are generally avoided, specific circumstances favor them. Connectivity between Asia and Europe typically traverses the Bab al-Mandab Strait, lands in Egypt near the Gulf of Suez, and crosses overland to the Mediterranean Sea. An alternative route passes through the Persian Gulf, Iraq, and Türkiye, though it requires transiting the Strait of Hormuz or crossing overland through Oman and the United Arab Emirates.
Cable Faults
Worldwide, approximately 200 submarine cable faults are reported each year—a figure the International Cable Protection Committee notes has remained relatively stable even as the global cable inventory expands. The cables themselves demonstrate remarkable reliability; rather, the maritime traffic operating above them accounts for the vast majority of failures. Approximately 86 percent of cable faults stem from fishing activity and vessel anchoring, with fishing incidents occurring roughly twice as frequently as anchor strikes.
Geological events, such as submarine landslides and seabed movements, account for roughly 7 percent of faults, while cable abrasion and component failures in repeaters account for 4 percent each.
Because faults strongly correlate with maritime activity, nearly half of all cable incidents occur within sovereign territorial waters, and most of the remainder happen within exclusive economic zones. Only 2 percent of faults occur on the high seas. Cables are inherently most vulnerable close to shore in shallow waters where fishing is concentrated, ships drop anchor, and multiple lines converge at coastal landing stations. The deep ocean remains the safest environment for subsea infrastructure.
National jurisdictions extend far beyond the low-water mark. Under the 1982 United Nations Convention on the Law of the Sea, sovereign territorial waters extend 12 nautical miles from a coast, while coastal states hold exclusive economic rights to seabed resources up to 200 nautical miles—or further, depending on the continental margin. Consequently, any physical intervention, construction, or repair operation concerning a submarine cable within these sovereign areas requires formal government authorization.
Location and Repair
Locating a cable break is technically straightforward. Transmitting an optical pulse yields a precise reflection at the break point, calculating the distance from the cable origin with high accuracy. From that point forward, however, the operation becomes a complex maritime undertaking.
Operators must contract a specialized cable repair ship and secure government permits to operate within territorial waters. Once on site, the vessel drags a grapnel along the seabed to snare the cable, cuts it, retrieves and buoys one end, and recovers the opposing end. A new section is spliced aboard the ship inside a jointing cabin, where individual fibers are fusion-spliced, tested, and sealed against deep-sea pressure before the repaired line is laid back onto the seabed with sufficient slack.
Single repairs typically cost between $500,000 and $1 million, depending on location, depth, weather conditions, and vessel availability. Although the total cable inventory has grown, obtaining repair permits in territorial waters has become increasingly difficult. Industry data indicates that average repair response times have more than doubled over the past decade, with the longest single repair in 2023 stretching to 947 days, largely due to administrative delays in securing government permissions.
Repair operations rely on a specialized global fleet of roughly 60 vessels. These ships operate under regional maintenance agreements that pool operational costs among cable owners across major geographic zones, including the Atlantic Ocean, the North American West Coast, the Mediterranean, Southeast Asia and the Indian Ocean, and Yokohama in the North Pacific.
Recent analyses by TeleGeography and Infra-Analytics indicate that approximately two-thirds of existing cable maintenance vessels will reach the end of their service lives by 2040, while total cable length is projected to grow by 48 percent over the same period. Closing this gap requires an estimated $3 billion investment to build 15 replacement vessels and five additional ships simply to maintain current service levels.
This dynamic highlights a central challenge in cable resilience. While laying new routes is commercially viable—frequently funded by hyperscale cloud companies with strong economic incentives—no individual cable generates enough revenue to justify maintaining a dedicated repair fleet. Consequently, the industry relies on shared maintenance pools that have historically been optimized for low costs rather than fleet renewal.
Investigating Cable Outages
Recent high-profile cable incidents have underscored these vulnerabilities. Investigations into various Baltic Sea disruptions and Asian strait outages often point to anchor dragging and severe weather as primary culprits, particularly among poorly maintained merchant vessels. For instance, investigations into certain Baltic incidents concluded they were accidental, while authorities in Taiwan and Hong Kong prosecuted captains involved in specific cable severing events. Other incidents, such as a Matsu fault in April 2026, were traced to the wreck of a stranded fishing boat shifting onto the cable line. Investigators emphasize that anchor dragging during heavy weather remains a frequent driver of ordinary faults, explaining why many inquiries yield accidental findings.
Who Is Responsible for Cable Resilience?
The operational model of subsea networks has evolved dramatically over recent decades. Traditional telecommunications systems treated each cable as a self-contained unit, with the owner maintaining independent resilience through ring architectures where traffic could dynamically reroute around a damaged segment. However, this redundancy doubled the required capacity, reflecting a 50 percent carriage efficiency that drove up costs.
In pursuit of more affordable services, internet service providers (ISPs) began purchasing non-backed-up capacity across multiple distinct cable systems. While an individual cable outage disrupted that specific route, ISPs could automatically reroute traffic across unaffected systems using standard internet routing protocols. Consequently, responsibility for network resilience shifted from individual cable operators to network operators, transforming sudden service failures into manageable drops in network performance.
Despite these adaptations, submarine cable systems remain a complex patchwork of private consortia, commercial repair fleets, national regulations, and outdated international conventions. Streamlining repair permits and establishing pre-agreed emergency procedures remain persistent industry goals. Without coordinated investment in an aging repair fleet and a commitment to route diversity over economic clustering, the global digital infrastructure will continue to grapple with structural vulnerabilities rooted not in technology, but in institutional and economic hurdles.
Looking Forward
The telecommunications consortium model that financed the majority of the world’s subsea cables thirty years ago has largely ended, and the service life of that infrastructure is expiring. Approximately one-quarter of the world’s current subsea cable length—representing 845,000 kilometers of fiber-optic cables laid during the late 1990s and early 2000s internet boom—is projected for decommissioning and retirement by 2030, alongside the retirement of major historical systems like TAT-8, TAT-14, SEA-ME-WE-3, and early trans-Pacific links.
In their place, new cable projects are increasingly funded or controlled by major digital technology firms. By 2028, individual technology companies are projected to control unprecedented shares of the global cable inventory, particularly across the Indo-Pacific and Atlantic regions. This centralization raises sovereign risk concerns among nations whose primary international communication conduits are owned and operated by foreign commercial entities.
As public telecommunications infrastructure transitions entirely into private corporate hands, accountability shifts away from public utility toward institutional investors focused on corporate valuation. Outside the United States, few economies possess the resources to counter this concentration, though the European Union has taken steps to fund repair vessels and enhance regional surveillance.
Ultimately, maintaining the resilience of the global communications infrastructure requires addressing ocean-level logistics, regulatory streamlining, and coordinated investment. The global cloud economy rests entirely upon the solidity of the seabed, and its reliability remains tied to the collective frameworks adopted to protect it.
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