CHRISTCHURCH, New Zealand — Taiwanese authorities this month charged the Chinese captain of the cargo vessel Hong Tai 58 for damaging an underwater communications cable connecting Taiwan to the Penghu Islands near the Chinese coast.
The legal move is a reminder that sabotage of vital seabed cables, which is notoriously difficult to prove, has firmly entered the canon of gray-zone tactics meant to find weak spots in an adversary’s defenses.
Taiwan’s coast guard had detained Hong Tai 58, a Togolese-flagged cargo vessel crewed by Chinese sailors, in late February.
A similar incident occurred north of Taiwan in January, but on that occasion a Hong Kong-owned commercial vessel was fingered as the culprit.
Taiwan has reported five cases of seabed cable damage this year already, compared with just three each in 2023 and 2024. Taiwan’s coast guard has created a blacklist of nearly 100 suspicious China-linked ships.
A growing problem
Despite Beijing’s denials, some observers believe such nefarious actions are part of China’s coercive behavior towards Taiwan.
During a House Armed Services Committee hearing in Washington earlier this month, for example, U.S. Sen. Jacky Rosen (D-Nev.) blasted China’s “reckless, coercive and aggressive activities,” singling out sabotage of undersea cables as a “particularly alarming tactic.”
At the same hearing, U.S. Navy Adm. Samuel Paparo, commander of Indo-Pacific Command (INDOPACOM), acknowledged attempts to sabotage undersea internet cables, particularly around Taiwan.
Wew weeks after Taiwan seized Hong Tai 58, media revealed that the state-owned China Ship Scientific Research Center had patented a deep-sea device “capable of severing the world’s most fortified underwater communication or power lines.”
One of China’s priorities in major hostilities against Taiwan – such as a naval blockade or full-blown invasion – would be to isolate the island and interfere with civilian and military communications.
Risk and redundancy
In his testimony to U.S. lawmakers, Paparo proposed two countermeasures against Chinese sabotage of cables. The first is to penetrate the targeting chain through intelligence gathering, and then showing up with forces “in the locations where they would be otherwise cutting those cables.”
Second, Paparo added, is resilience. This encompasses redundant communication networks to ensure the information environment continues unabated, as well as the proliferation of multiple satellite constellations in low Earth orbit.
Meanwhile, naval tech companies are sensing a new market for their equipment.
Andy Keough, managing director of Saab Australia, said the company is well positioned to support governments in defending underwater infrastructure through its countermine portfolio.
“Our products play a crucial role in mine countermeasure solutions as well as the protection of critical undersea infrastructure, including pipelines and subsea cables, across the globe,” Keough said.
Autonomous underwater vehicles, or AUVs for short, can monitor infrastructure, and seabed sensors can provide real-time maritime domain awareness.
Developing the ability to quickly repair infrastructure or reroute communications is also important. For example, Saab’s electric Work-Class Remote Operated Vehicle can operate at depths of 5,500m and is controlled via satellite link. For inspections and repairs, the company’s Sabertooth AUV can act as a persistent underwater resident with the aid of a subsea docking station, said Keough.
Elsewhere, the company Exail won a French military contract to design an AUV that can dive as deep as 6,000m to counteract seabed warfare. To be delivered in 2027, these vehicles have the ability to reprogram themselves mid-mission. For example, if one detected something suspicious, it could move into observation mode to watch what a given target is doing.
Thales Australia hopes to attract new customers with its sensing equipment. Gavin Henry, of the company’s undersea warfare unit, said Thales’ Blue Sentry technology, with its thin-line towed array, can help find potential threats.
“This system employs a network of sophisticated sensors capable of detecting and tracking both surface and underwater contacts,” he said.
Maritime domain awareness
Ross Babbage, CEO of Strategic Forum in Australia, argues the undersea threat to key infrastructure requires a layered, whole-of-nation approach.
“In conjunction with automatic identification systems on ships, you can make sure people are following the correct channels and their prescribed route, because they’re only going to do these things if they deviate from their normal route,” he said. “So there are bell ringers there to then target an asset to go and have a look.”
Nations like Australia need to conduct surveillance and look for anomalies, Babbage said. “If you can do that, then you can pinpoint those anomalies and start to put the heat on them before they do it, or certainly capture them after they’ve done it, as they’ve done in Europe, and deal with it on a diplomatic basis.”
An Australian Defense Department spokesperson told Defense News the military has a range of capabilities to monitor and respond to threats to undersea communication cables.
The Australian Defence Force works with other agencies specializing in cybersecurity to protect infrastructure, though much of that information is classified.
Gordon Arthur is an Asia correspondent for Defense News. After a 20-year stint working in Hong Kong, he now resides in New Zealand. He has attended military exercises and defense exhibitions in about 20 countries around the Asia-Pacific region.
