The undersea cable war

Summary
Russia and China are suspected of targeting these key data channels.A handout picture released by the Britain's Ministry of Defence (MOD) in London on January 22 shows Royal Navy Type 23 frigate HMS Somerset (foreground) patrolling near the Russian vessel Yantar, near U.K. waters, earlier this week.
NATO said last week it’s sending frigates, aircraft and naval drones to patrol the Baltic Sea, and the question is what took so long. The deployment follows multiple suspected acts of sabotage targeting Europe’s undersea cables. Add another threat to the West’s burgeoning list.
Nearly all of the world’s international data is transmitted through subsea fiber-optic cables. The French government recently described them as “the accessible physical layer of cyberspace," and they’re vital for everything from financial transactions to diplomatic communications to video streaming.
That makes cables a prime military and espionage target. The Yantar, a Russian spy ship “used for gathering intelligence and mapping the U.K.’s critical underwater infrastructure," is now in the North Sea after sailing through the English Channel, British Defense Secretary John Healeysaid Wednesday. In November the U.K. detected the Yantar “loitering over critical undersea infrastructure."
On Christmas Day a cable connecting Finland and Estonia was damaged by an anchor dragged across it. Finnish authorities detained crew members and a tanker identified by the maritime-traffic analytics company Lloyd’s List Intelligence as part of a Russia-linked shadow fleet. The probe continues, but the lead investigator this week described “suspicions of deliberate action."
Two more Baltic cables—one between Sweden and Lithuania and another between Germany and Finland—were severed a month earlier. “No one believes these cables were accidentally severed," said German Defense Minister Boris Pistorius in November. The investigation has focused on a Chinese commercial vessel that had left a Russian port, then sailed alongside both cables.
The U.S. noted Russia’s ability to target Western undersea infrastructure in a 2024 annual threat assessment. The British think tank Policy Exchange cites “eight unattributed yet suspicious cable-cutting incidents in the Euro-Atlantic" since 2021, “and over 70 publicised sightings of Russian vessels behaving abnormally near critical maritime infrastructure."
Taiwan suspects China was responsible for damage to an undersea cable off its northern coast on Jan. 3. China denies it. But Taiwan says Chinese vessels also severed deep-sea cables in 2023 and cut off Internet access for 14,000 residents of Matsu Island. Taiwan is beefing up its maritime surveillance within 24 nautical miles of its coast.
The threat to undersea cables is a classic example of asymmetric vulnerability for a West that relies on data networks and communications for daily living. An anchor dragged by a rickety vessel along the sea floor can snap a cable while also offering plausible deniability to adversaries. And fixing cables is expensive and time-consuming. There are only a few special repair vessels worldwide.
Increased military surveillance at sea is a good first step, though the West lacks the resources to monitor all of this vast infrastructure. Artificial intelligence and detection technologies can help countries focus on suspicious activity and respond more efficiently, but this threat also underscores the importance of Western naval power.
Under the current legal framework, victims have little legal recourse to prosecute or punish those who sabotage cables in international waters. The U.S. and Europe will also have to consider how to respond so hostile actors don’t enjoy impunity when sabotage occurs.
Meanwhile, redundancies in cables can mitigate the risks of serious disruption, and reducing red tape and streamlined permitting would encourage cable construction and hasten repairs. This is a vital project for the Trump Administration and U.S. allies.