China brandishes cutter for snipping deep-sea cables

Asia Times

26-03-2025

China has unveiled a compact device for cutting deep-sea cables, introducing a potential new dimension in underwater warfare.
This month, the South China Morning Post (SCMP) reported that China has unveiled a deep-sea cable-cutting device capable of slicing through the world's most fortified undersea communication and power cables at depths of up to 4,000 meters.
Built by the China Ship Scientific Research Centre (CSSRC) in collaboration with the State Key Laboratory of Deep-Sea Manned Vehicles, the device is designed for use with China's sophisticated submersibles, including the Fendouzhe and Haidou series.
While officially presented as a tool for civilian salvage and seabed mining, the device clearly has dual-use potential. The tool utilizes a diamond-coated grinding wheel spinning at 1,600 revolutions per minute, mounted on a submersible-compatible platform with a 1-kilowatt motor, to cut through steel-armored cables that carry approximately 95% of the world's data.
Its titanium shell and pressure-resistant seals allow operation in extreme depths, with robotic arms enabling use in low-visibility conditions.
The disclosure, published this February in the journal Mechanical Engineer, marks the first time a nation has officially revealed such a capability. Analysts warn that the tool could covertly target strategic chokepoints, such as Guam, a linchpin in US Indo-Pacific defense.
The announcement comes amid China's deep-sea fleet expansion and its growing technological edge over aging US and Japanese counterparts, heightening global concerns about undersea security.
Underscoring the threat to undersea cable infrastructure, Raghvendra Kumar mentions in a 2023 Journal of Indo-Pacific Affairs article that sabotaging such infrastructure could be viewed as a prelude to kinetic warfare. Aside from cables, Kumar points out that landing stations are also vulnerable targets for sabotage.
Kumar also notes that undersea cables and landing stations are high-value targets for espionage, with such operations often conducted covertly to intercept the data flowing through the infrastructure.
In line with that, Sam Dumesh mentions in an American Security Project (ASP) article this month that a breach of cable landing stations could allow China to reroute internet traffic, including US-based services. Dumesh points out that access may already be assured if such data is rerouted to Chinese-owned infrastructure.
While he says encryption can help secure compromised data, such data can be harvested, stored and decrypted later using quantum computing technology.
Despite the threat of US data routed through China-controlled undersea cable infrastructure, Anna Gross and other writers mention in a June 2023 Financial Times (FT) report that the US has, with relative success, blocked China out of most undersea cable projects.
However, Gross and others point out that China has responded by implementing undersea cable projects in friendly countries, raising concerns about who owns and manages the global Internet infrastructure.
Given those threats, China's unveiling of its deep-sea cable cutter device possibly amplifies the vulnerability of undersea cables surrounding Taiwan and Guam.
In a July 2024 report for the Stanford Global Digital Policy Incubator, Charles Mok and Kenny Huang note that Taiwan's digital lifeline relies on 15 undersea cables that carry over 100 terabits per second of bandwidth; however, this vital infrastructure is acutely vulnerable to both natural and man-made disruptions.
Mok and Huang note that Taiwan is surrounded by seismically active seas and dependent on foreign repair ships, of which only 22 globally are dedicated to maintenance.
As a result, they mention Taiwan faces logistical delays in restoring connectivity after damage. They point out that incidents such as the repeated severing of cables to Matsu Island, allegedly by Chinese vessels, highlight risks of strategic sabotage.
Compounding the threat, they note that the global cable repair industry is overstretched, while Taiwan lacks domestic repair capabilities, making its network resilience precarious amid rising geopolitical tensions.
As with Taiwan, Teleguam Holdings points out that Guam is dubbed 'The Big Switch in the Pacific,' as its position in the Pacific connects the Indo-Pacific with the US west coast. Teleguam Holdings emphasizes that the island's strategic location between the US and Asia offers a direct route for data transmission, which decreases latency and enhances bandwidth.
Teleguam Holdings reports that Guam hosts 12 undersea cables, providing robust connectivity and redundancy, establishing the island as a digital link.
Highlighting the potential military consequences of major cable breakages in Taiwan, Yau-Chin Tsai notes in an August 2023 article for the Institute for National Defense and Security Research (INDSR) that submarine cables remain the primary connection between Taiwan and its frontline islands, such as Dongyin and Matsu.
Tsai mentions that severing the connecting cables could paralyze the islands' defenses, making Taiwan unable to use its military capabilities fully.
However, Elizabeth Braw points out in a January 2025 Foreign Policy article that during an undersea cable break between Matsu and Taiwan that month, line-of-sight microwave transmission and satellite internet ensured that most of the former's 12,000 residents remained unaffected.
Similarly, Andrew Niedbala and Ryan Berry mention in an August 2023 Proceedings article that a coordinated severing of undersea cables connecting Guam, Asia, Hawaii and the US could result in an information blackout, significantly impairing US military command and control capabilities.
However, China's announcement of its deep-sea cable-cutting device may be more propaganda than actual capability.
In a Lowy Institute article this month, Cynthia Mehoob points out that China's claims may not align with technical realities. Mehoob mentions that undersea cables are neither armored nor notably fortified at extreme depths, such as 4,000 meters.
She notes that undersea cables are typically 17 to 21 millimeters thick at extreme depths and armored cables may be employed where the seabed terrain is exceptionally rugged; however, using such cables generates additional challenges. She points out that armored cables are difficult to bend, and bringing them up to the surface for repairs is costly.
Additionally, Mehoob notes that armoring cables is a standard practice only in shallow waters at 1,500 meters, where there is a real risk of damage from anchors and fishing activities. She notes that at extreme depths, armored cables could snap under their weight, rendering such protective measures counterproductive.
Mehoob says China's announcement is part of a carefully orchestrated propaganda campaign – first published in a peer-reviewed journal, then disseminated through a major media outlet such as SCMP, and subsequently amplified through sensationalist global media coverage.
The goal, she says, is to assert deterrence capabilities, project power and extend its maritime reach without actual conflict. Whether a real threat or clever theater, China's cable cutter signals a new era in which information warfare may begin not in cyberspace but 4,000 meters under the sea.