The Matsu Islands, an archipelago of 36 islands in the East China Sea situated alongside the southeastern coast of mainland China, have been administered since 1949 by Taiwan. These territories are part of a larger set of outlying islands managed by Taiwan, including the Kinmen and Penghu chains, all of which lie within the strategic waters of the Taiwan Strait. To maintain continuous connectivity with the main island of Taiwan, the Matsu archipelago relies on a network of critical submarine communication lines, specifically the Taima No.2 and Taima No.3 cables, with Taima No.4 scheduled to join them soon.
Because the Taiwan Strait is a relatively shallow body of water with an average depth of just 70 meters, the submarine cables resting on its seafloor are perpetually exposed to potential damage from maritime activities. Common hazards include being snagged by heavy fishing equipment or anchored by commercial vessels. However, these specific cables have endured an extraordinary run of misfortune. Between 2018 and 2022, lines connecting Taiwan to the Matsu Islands were severed an astonishing 27 times, followed by four major outages during the three-year span from 2023 to 2025.
This localized vulnerability is part of a much broader global pattern. The Baltic Sea, another shallow body of water hosting roughly a dozen submarine communications cables alongside underwater electricity and gas pipelines, has recorded 11 disruptions to its subsea systems since 2023 alone. Across the globe, an estimated 1.5 million kilometers of subsea communications cables power 607 in-service submarine cable systems. These networks form the absolute backbone of international telecommunications services. In the event of a catastrophic and widespread failure, existing satellite constellations are wholly unequipped to handle the immense volume of global data traffic. Such a scenario would leave isolated communities completely cut off, triggering severe logistical, economic, and societal ramifications worldwide.
As the global community increasingly relies on these subsea networks, they are rightly treated as critical infrastructure requiring rigorous resilience planning. Yet, modern geopolitical tensions and warfare have introduced deliberate disruption as a dangerous new variable, compounding the traditional risks posed by geological activity and accidental maritime damage.
Historical precedent highlights how vulnerable these networks have always been to state-sponsored sabotage. 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 heavy grappling hooks along the seabed, the vessel hauled up five German transatlantic and European telegraph cables and severed them. This decisive action cut 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 could readily intercept and decode. Breaking German cryptographic codes enabled the British to track crucial military movements and capture pivotal messages, such as the infamous Zimmermann Telegram. The deliberate cutting of undersea cables was repeated by British forces in September 1939, when lines connecting Germany to Lisbon and New York were similarly destroyed.
Protecting the Cable
Constructed from thin, polyester-coated fibers resting at the bottom of the ocean, submarine cables face constant threats from various environmental and human factors. To defend against these risks, engineers wrap the inner core of fiber optics and its copper conductor sheath in additional layers of steel cable jacketing. This heavy-duty armor is primarily deployed to minimize vulnerabilities stemming from commercial shipping and fishing accidents.
However, cross-sectional representations often present a misleading picture, typically depicting the heavily armored cable segments utilized near coastal landing stations. In contrast, deep-sea cable segments laid across the ocean floor discard all external armor elements entirely. These deep-water sections consist solely of inner components: optical fibers and a single thin steel thread wrapped in silicone gel, surrounded by a copper sheath used to power cable repeaters, and encased in polyethylene. Measuring approximately 20 millimeters in diameter—roughly the size of a garden hose—these unarmored lines rely entirely on the vast depth of the ocean for protection.
A cable eventually surfaces at a designated cable landing station, typically a secure, plain facility equipped with reliable auxiliary power. Planners deliberately choose coastal locations characterized by low volumes of fishing or maritime traffic and a steep upward slope from the deep-sea floor. Because cables face their greatest risks from coastal shipping and shallow-water activities, minimizing the distance between the deep-sea floor and the dry-land station is a primary engineering objective. Many national jurisdictions also establish official Cable Protection Zones, warning marine operators to strictly avoid anchoring or conducting fishing activities within these designated subsea corridors.
Cable Routing
Network architects must carefully balance competing objectives when planning resilient cable routes. Ideally, a cable path should be as short as possible to reduce capital expenditure and minimize end-to-end signal latency. At the same time, routes must avoid active geological zones such as tectonic plate boundaries and mid-plate rifts. While deeper ocean placement offers superior protection against shipping traffic and hostile interference, extreme depths make locating and retrieving a cable for maintenance exceptionally challenging.
Geographic choke points present another major hurdle. The Bab al-Mandab Strait, for instance, serves not only as a vital surface shipping lane between the Indian Ocean and the Red Sea but also as a concentrated conduit for 16 major subsea cables. In September 2025, several cables passing through the strait were severed, disrupting an estimated 25% of the total communications capacity linking Asia, Europe, and the Middle East. Because the surrounding waters remain controlled by Houthi forces, the region is functionally ungovernable for routine cable protection and maintenance operations.
Similar concentration risks exist in the Singapore Strait, a shallow waterway hosting 35 distinct cable systems alongside heavy maritime traffic. Further north, the Luzon Strait between Taiwan and the Philippines channels 18 cables. In December 2006, a major earthquake triggered submarine landslides in the Luzon Strait that severed every cable running through the passage and buried many under deep layers of sediment, requiring 11 repair vessels 49 days to fully restore operations. Meanwhile, the Black Sea presents severe geopolitical risks and regulatory gaps; while naval mines pose a confirmed danger, ongoing conflict has made the region completely inaccessible for routine maintenance.
Geopolitical considerations heavily influence routing decisions as well. Owners actively avoid unstable territorial waters when viable alternatives exist. Furthermore, regulatory frameworks impose strict constraints. Cables landing in United States territory fall under Federal Communications Commission oversight, which includes bans on equipment or services from companies deemed national security threats. The FCC has also blocked cable landings when lines originate or terminate in territories classified as foreign adversaries. While land routes are generally avoided, certain corridors—such as overland paths through Egypt connecting the Red Sea to the Mediterranean, or alternative routes through the Persian Gulf, Iraq, and Türkiye—are utilized to bypass vulnerable maritime choke points like the Bab al-Mandab Strait.
Cable Faults
Globally, approximately 200 submarine cable faults are reported each year, a figure that the International Cable Protection Committee notes has remained relatively stable even as the total inventory of installed cable expands. The physical cables themselves demonstrate remarkable reliability; the maritime traffic moving above them is responsible for the vast majority of failures. Statistics show that roughly 86% of cable faults stem from fishing activity or commercial anchoring, with fishing operations accounting for twice as many incidents as dropped anchors.
Geological occurrences, including submarine landslides and seabed movements, account for about 7% of faults. Cable abrasion causes 4%, while internal component failures within repeaters represent just 4% of disruptions. Because faults correlate so strongly with human maritime activity, nearly half of all incidents occur within sovereign territorial waters, with most of the remainder happening inside exclusive economic zones. Only 2% of faults occur out on the high seas. Cables remain highly vulnerable close to shore where shallow waters concentrate fishing fleets, commercial anchors, and landing infrastructure. The deep ocean, largely devoid of fishing and anchoring, remains the safest environment for subsea telecommunications.
National jurisdictions extend far beyond the low-tide mark. Under the 1982 United Nations Convention on the Law of the Sea, sovereign territorial waters stretch 12 nautical miles from a coast, while coastal nations maintain exclusive economic rights over seabed resources up to 200 nautical miles or more offshore. Consequently, any physical intervention, construction, or repair operation involving a submarine cable within these sovereign zones requires formal government authorization.
Location and Repair
Locating a cable break is technically straightforward. Technicians send an optical pulse down the fiber, and the reflection pinpointing the break distance can be measured with high precision. Once the location is identified, the challenge shifts to maritime execution.
Operators must dispatch a specialized cable repair ship, which must first secure government permits to operate within territorial waters. Once on site, the vessel drags a heavy grapnel along the seabed to snare the cable, cuts it, recovers and buoys one end, and brings the other end aboard. A new section of cable is spliced into place inside a jointing cabin, where individual optical fibers are fusion-spliced and thoroughly tested. The protective joint is then rebuilt and sealed against extreme ocean pressure before the repaired line is lowered back to the seabed with sufficient slack to prevent future tension.
A single repair typically costs between $500,000 and $1 million, depending heavily on water depth, location, weather conditions, and contracting arrangements. While global cable mileage has grown, obtaining governmental repair permits 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 consumed by waiting for official clearance.
Compounding this delay is an aging fleet of repair vessels. Roughly 60 ships worldwide handle submarine repairs, operating under pooled regional maintenance agreements across the Atlantic, the North American West Coast, the Mediterranean, Southeast Asia, the Indian Ocean, and the North Pacific. Analysis by TeleGeography and Infra-Analytics reveals that approximately two-thirds of these maintenance vessels will reach the end of their service lives by 2040. Over the same timeframe, total subsea cable length is projected to grow by 48%. Closing this infrastructure gap requires an estimated $3 billion investment to build 15 replacement ships and 5 additional vessels merely to maintain current service levels. However, because cable maintenance has traditionally been funded through lean shared agreements optimized for minimal cost, financing a fleet renewal remains a complex economic challenge.
Investigating Cable Outages
Recent high-profile cable outages have drawn intense international scrutiny. Incidents involving vessels such as the Yi Peng 3 in the Baltic Sea, the Eagle S near Finland, the Hong Tai 58 near Taiwan, and the Newnew Polar Bear have frequently sparked suspicions of deliberate sabotage. Yet official investigations often reveal more mundane causes. Swedish authorities found no conclusive evidence of wrongdoing in the Yi Peng 3 case, ruling the January 2025 Latvia-to-Gotland damage accidental, and a Finnish court subsequently dismissed charges against the captain of the Eagle S. Similarly, US and European officials concluded that several Baltic disruptions were unintentional. In other instances, legal accountability was established; the captain of the Hong Tai 58 was convicted in Taiwan over damage to the Penghu No. 3 cable, while an April 2026 Matsu fault was traced to the shifting wreck of a stranded local fishing boat.
Anchor dragging remains an everyday hazard, particularly among poorly maintained merchant vessels operating in severe weather. This persistent reality explains why maritime investigators frequently reach inconclusive findings regarding suspected foul play.
Who Is Responsible for Cable Resilience?
The underlying architecture of global telecommunications has evolved dramatically. Under the legacy telephone network model, each cable operated as a self-contained system where individual owners maintained complete responsibility for resilience. Telephone routing utilized ring architectures, instantly diverting voice traffic along alternate pathways if a primary line failed. While this dual-path design guaranteed immediate failover, it meant actual usable capacity was halved, reflecting a 50% carriage efficiency that drove up costs.
In pursuit of cheaper bandwidth, Internet Service Providers demanded non-backed-up capacity priced to match modern packet-switched efficiencies. Rather than paying for dedicated redundant lines, ISPs purchased capacity across multiple distinct cable systems. When an individual cable failed, network routing protocols automatically rerouted traffic over unaffected systems. Consequently, responsibility for resilience shifted from the individual cable operator to the wider internet network operator. While an outage caused a localized drop in capacity, the elasticity of internet traffic typically resulted in a minor performance dip rather than a catastrophic service shutdown.
Resilience and Critical Infrastructure Considerations
Submarine cable systems are constructed by private consortia, maintained through commercial pooling agreements, regulated independently by coastal states, and governed by international maritime conventions drafted long before the modern internet existed. Streamlining permit approvals and establishing pre-agreed emergency procedures across national boundaries would significantly reduce outage durations. However, financing the renewal of an aging global repair fleet remains an unresolved systemic risk.
Geographic choke points, geological hazards, and changing seabed conditions will continue to threaten subsea infrastructure. While route diversity offers an effective defense, economic pressures work against it. Cable operators naturally favor the shortest, most cost-effective paths and lack individual incentives to fund longer, diversified routes.
Looking Forward
The traditional telephone consortium model that financed the majority of the world’s subsea cables three decades ago has effectively concluded, and the operational lifespans of those early assets are drawing to a close. Projections indicate that roughly a quarter of the world’s current subsea cable length—representing some 845,000 kilometers of fiber optics laid during the late 1990s and early 2000s tech boom—will be decommissioned and retired by 2030. Historic Atlantic systems like TAT-8 and TAT-14, the Europe-Asia SEA-ME-WE-3 line, and major trans-Pacific links between Japan, China, and the US have already ended or are ending operations. Concurrently, more than half of the existing repair vessel fleet will reach retirement age by 2040.
In place of legacy consortia, new cable projects are increasingly funded by major US cloud and technology giants. This shift raises sovereign risk concerns among nations whose primary international communications links are owned and operated by foreign commercial entities. Furthermore, it concentrates control over maintenance pooling agreements and specialized repair fleets within a handful of corporate hands. By 2028, Google is projected to own the largest share of subsea cables measured by kilometers across the Pacific, Atlantic, and Indian Oceans, controlling over 50% of the entire inventory in the Indo-Pacific region.
This high degree of corporate centralization gives a single private entity unilateral control over maintenance arrangements and repair logistics for critical global communications infrastructure. Accountability for these corporate giants rests primarily with institutional investors focused on profitability rather than broad public service mandates. Outside the United States, few economies possess the resources to counter this trend independently. While the European Union has taken steps to fund regional repair vessel capacity and enhance subsea surveillance, broader global coordination remains scarce.
Ultimately, maintaining the resilience of global communications is fundamentally an ocean infrastructure challenge. Preserving the integrity of the seabed requires streamlined international cooperation, diversified routing strategies, and sustainable financing models for maintenance fleets. The digital economy may project an image of weightless, borderless cloud computing, but its continued stability rests entirely upon the physical solidity of the ocean floor—and the collective governance frameworks we establish to protect it.
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