Strategic shockwave: World's deepest cable-cutter gives China stealth edge, shifts balance in maritime warfare

China has quietly unlocked a new lever of power beneath the waves. In a rare disclosure, it has unveiled a compact deep-sea device capable of slicing through even the world’s most reinforced undersea cables — a move that could redefine maritime security. Designed to operate at depths of 4,000 metres — twice the maximum range of most subsea networks — the tool introduces a new layer of vulnerability to the ocean floor’s critical infrastructure.

This is the first time any nation has officially acknowledged possessing a device with such capabilities — one that can target the arteries of global communication and energy grids.

Developed by the China Ship Scientific Research Centre (CSSRC) and the State Key Laboratory of Deep-Sea Manned Vehicles, the cutter is tailored for deployment via China's advanced submersibles like the Fendouzhe (Striver) and the Haidou series.

How it works

Conventional tools fail against heavily armored undersea cables. To overcome this, Chinese engineers built a 150mm diamond-coated grinding wheel that spins at 1,600rpm — strong enough to pulverize steel without stirring up sediment. The mechanism runs on a one-kilowatt motor coupled with an 8:1 gear reducer for efficient torque, though sustained operation at full depth risks overheating.

Encased in a titanium alloy shell and sealed with oil-compensated barriers, the device is engineered to survive crushing pressures at 4,000 metres. It's maneuvered by robotic arms in near-total darkness, guided by high-precision navigation systems.

Military use potential

While the tool is promoted for seabed mining and salvage, its military potential is unmistakable. Stealthily severing undersea cables could cripple communications in a crisis — a strategic lever few countries possess.

One major vulnerability is Guam — a key hub in the US Indo-Pacific military network and a landing point for more than a dozen undersea fiber-optic cables used by military and tech giants like Google. In a conflict, taking Guam offline could shatter communications and disrupt global financial flows.

China's deep-sea ambitions  

This device is just one piece of a larger push. China now operates the world’s largest fleet of manned and unmanned submersibles. In February, it began constructing an underwater "space station" 2,000 metres deep in the South China Sea, designed to support six-person month-long missions.

The timing of this development is notable. Undersea infrastructure is increasingly under threat. Since 2023, the Baltic Sea has seen 11 incidents of cable damage, prompting fears of sabotage.

In Taiwan, suspicions of Chinese interference are rising. Authorities recently seized the Hong Tai 58 — a Chinese-crewed cargo ship — after it was linked to severed telecom lines. Taiwanese officials reported five cable-cutting incidents in 2025 alone, compared to three each in 2023 and 2024, heightening alarm amid escalating Taiwan Strait tensions.