Be ready for the new Cold War, under the sea

There has been in the past weeks an alarming surge in reports of cuts to undersea cables. In the Baltic Sea, telecommunications links and power lines have been severed. Cables to Taiwan have been sabotaged in recent days, part of a series of incidents that extends back several years.

These attacks — there is no other word — are examples of “gray zone” tactics, or attempts to pressure adversaries that remain below the threshold of war and thus defy a simple or clear response. Difficult to attribute and indirect in effect, these tactics nevertheless impose real costs and can be as destabilizing as an actual military attack. In some cases, they are the precursors of kinetic action.

We have taken for granted the significance of these cables and are only now waking up to their vulnerability. Protecting them is near impossible: There are too many, they are too scattered and they are too difficult to continuously surveil. Still, we must prepare and there are steps that can be taken to reduce the impact of those attacks and improve the chances of deterring them.

Submarine cables have a long history. The first was laid across the English Channel in 1850 to transmit telegraph messages between England and France. Japan got its first in 1872. Today, an estimated 529 cable systems that stretch approximately 1.6 million kilometers carry virtually all — an estimated 99% — of intercontinental internet traffic and data and voice communication.

These cables are the backbone of modern society, facilitating trillions of dollars of daily electronic financial transactions, ordinary international communications (and even domestic traffic can be routed overseas for practical reasons), the transmission of mindless videos and sensitive government messages. They are truly vital infrastructure.

They will become more significant still. It is estimated that global mobile data traffic will grow 28% each year until 2030, reaching 603.5 million terabytes per month.

Experts reckon that there are about 150 to 200 submarine cable faults each year, most of which are the result of natural events — such as underwater avalanches or the earthquake that hit Japan in March 2011 — or are genuine accidents. In the vast majority of cases, the damage goes unnoticed since providers have built redundancy into the system: When one cable goes down, the traffic is automatically routed to another.

In a growing number of cases, however, the damage appears to be deliberate. Since 2022 and the start of the Ukraine war, there have been at least three reported cases of possible sabotage to telecommunications cables and gas pipelines that traverse the Baltic Sea, a fairly shallow waterway in the heart of northern Europe that is bordered by eight NATO countries and Russia.

In October 2023, the Chinese ship Newnew Polar Bear dragged its anchor, damaged cables and a pipeline linking Estonia to Finland and Sweden. In November last year, a Chinese bulk carrier with a Russian captain severed two undersea cables in Swedish waters. In a December 2024 incident, a tanker carrying Russian oil is thought to have dragged its anchor across the seabed to break two cables, one linking Finland and Germany, the other Sweden and Lithuania.

In each case, the actions were either denied or dismissed as an accident; proving otherwise has been difficult, even when the ships and governments allegedly involved have been examined by coast guard or law enforcement authorities. The evidence is compelling, however. In all the cases, the ship’s travel pattern puts it in the right place at the right time. In one case, the ship’s transponder was turned off just before the incident. In another, the anchor was dragged for 180 km, quite a distance to go unnoticed.

The challenge is equally if not more severe in the Asia-Pacific region, where the concentration of cables is perhaps the greatest in the world. At least 11 cable systems with multiple strands lie below the South China Sea and they are the key connections for Southeast Asia, Northeast Asia and the Asian mainland.

According to the International Cable Protection Committee, heavy traffic in the South China Sea — trillions of dollars of shipping and extensive fishing — renders cables there more prone to damage than virtually anywhere else. At least one cable fault is reported in the waterway every few weeks; in other parts of the world it’s one incident a year.

Here, too, there has been cable-cutting. The Taiwan government identified 12 cases of subsea cable damage due to “external forces” in 2023 alone.

In that year, two cables connecting Taiwan and the Matsu Islands were cut, allegedly by two Chinese civilian vessels, disconnecting the islands from the internet for almost two months. Last week, a Chinese-owned cargo vessel damaged an undersea cable near Taiwan’s northeast coast, an act that Taiwanese officials call sabotage. They also noted the Chinese involvement in the Baltic incidents, although Taiwan’s coast guard conceded that “it is not possible to confirm the real intention.”

China’s claim to virtually the entire South China Sea has also complicated maintenance and repair work on existing cables and hopes for laying new ones. Companies have noted that it takes longer to get approvals for work in the area and there is unease in some capitals about Chinese involvement in the construction or operation of those systems; they fear that the traffic could be surveilled or blocked.

To address elements of this problem, the United Nations last year created its first advisory body on subsea cable networks, the International Advisory Body for Submarine Cable Resilience. Its primary objective is to find common ground on “basic cable resiliency practices,” such as protection from accidents and ways to facilitate permit approvals from governments when damage occurs in territorial waters. It held its first virtual meeting last month and the first undersea cable summit will convene next month in Nigeria.

The group will avoid hard topics like security, which means that additional efforts are needed. Japan and like-minded countries might want to take a page from European governments. NATO last May launched the Maritime Center for Security of Critical Undersea Infrastructure, which aims to map all critical infrastructure in NATO-controlled waters and identify weak spots. The NATO Center for Maritime Research and Experimentation is working on ways to map the seabed.

Two key principles should be foremost in mind. First, create resiliency to minimize the damage if one or several cables are cut. This means creating alternative communications links. Second, like-minded governments should set up surveillance, monitoring and repair systems so that they are ready when such an incident occurs. This can help identify the culprit, which by itself should strengthen deterrence.

Protection will be difficult. Cables are often in the same area and their routes are public information. In some cases, cables run through international waters where there are no laws to hold saboteurs accountable. Sea conditions make repair and surveillance a challenge.

Most significantly, however, law breakers know that attribution is very hard and in the absence of a will to respond to such attacks, more will occur.