Undersea conflict: Russia's covert cable warfare strategy

The tanker Eagle S, stopped by Finnish special forces, formally sails under the flag of the Cook Islands. In practice—as the Finns themselves admit—the ship most likely conducted activities for the benefit of Russia.

In addition to demolishing underwater infrastructure connecting Finland and Estonia, the ship also acted as a floating spy—its deck was equipped with equipment typical of SIGINT (signals intelligence) vessels.

The events of December 2024 are just one episode of an undeclared war waged by states unfriendly to the West. A civilian vessel dropping anchor and dragging it along the seabed has occurred before.

The Chinese ship Yi Peng 3 damaged telecommunications cables linking Lithuania with Sweden and Finland with Germany. In contrast, another Chinese vessel, Newnew Polar Bear, damaged the Balticconnector gas pipeline and (probably) a telecommunications cable connecting Finland and Estonia.

The use of civilian ships is just one of the many available options. For years, intelligence agencies have focused on Russian "academics"—ships Russia has termed research vessels, bearing the names of distinguished Russian scholars, which are formally used for seabed research.

Units such as "Akademik Boris Petrov," "Akademik Tryoshnikov," "Akademik Nikolai Strakhov," and the newest one, "Yantar," commissioned in 2015, are equipped with various types of manned and unmanned underwater vehicles.

An example is the AS-37 underwater vehicle developed during the USSR era. It is equipped with an ARS-600 manipulator, and its two-person crew can operate at depths of up to 6,000 metres.

As civilian units, these ships are equipped with AIS (Automatic Identification System). Thanks to this system, it is known that the Russians are thoroughly examining the ocean floors in areas where critical global economic undersea cables lie, such as the North Atlantic or the eastern coast of the United States.

In addition to civilian units, Russia also has special forces intended for sabotage in deep waters. These forces are subordinate to the Main Directorate of Deep-Sea Research of the Russian Ministry of Defence (GUGI). Not much is known about them—even the approximate time of their creation, estimated to be in the 1960s.

GUGI was most likely established in response to the SOSUS system, a secret system of underwater sensors deployed in the Atlantic by NATO to monitor the movements of Russian submarines. These units, heading to the open ocean, had to navigate the so-called GIUK gap—a relatively narrow area between Greenland, Iceland, and the UK, where SOSUS enabled their detection.

To destroy these sensors, the Russians created military forces capable of conducting reconnaissance and sabotage at depths of thousands of metres. Nowadays, GUGI's tasks include attacking various kinds of undersea infrastructure and securing installations belonging to Russia.

A fire that broke out in 2019 on the AS-12 Losharik submarine gave a glimpse into the significance of these forces. Although measuring only about 70 metres in length, the submarine is equipped with a nuclear propulsion system. Thanks to its external, lightweight hull, Losharik appears like a regular submarine, but its internal pressurised hull forms seven spherical, interconnected chambers capable of withstanding very high pressure. It is estimated that with such a construction, Losharik can operate at depths of up to 2,500 metres.

When the fire occurred in 2019, among the 14 crew victims, seven held the rank of commodore (equivalent to colonel), and the others were officers of a rank not lower than lieutenant commander (equivalent to major). Two of the deceased officers received the Russian Hero Star, the highest combat decoration awarded in the Russian fleet.

Due to its small size, the AS—12 Losharik would not provide the crew with adequate comfort for long voyages. Therefore, during an 18-year reconstruction, a large Delta IV-type vessel (K-64, renamed BS-64 Podmoskovye) was adapted to carry the Losharik attached to its hull.

This adaptation allows the crew of the smaller vessel to enjoy much more comfortable conditions aboard the larger vessel for most of the mission. According to Russian sources, the vessel's renovation after the fire was completed by 2024.

The threat may not only come from humans. In September 2024, in Risavika Bay, southern Norway, the body of Hvaldimir was found. This was the name of a male Beluga whale (a marine mammal from the narwhal family) that appeared a few years ago near the Norwegian island of Ingøya.

He had a harness with a handle for a camera or photographic apparatus, bearing an inscription indicating that the accessory came from St. Petersburg. As it soon became clear, Hvaldimir was accustomed to human presence and cooperation. This sparked speculation that Russians might have trained the beluga to sabotage underwater or protect against it.

Attacks on underwater infrastructure are not solely actions at great depths. In the Kaliningrad Region—just a few miles from the Vistula Spit—the military unit No. 43104, the 390th Special Purpose Reconnaissance Point of the Baltic Fleet, is based.

Alongside the centre, hidden in the woods yet visible from satellites in the Parusnoje area, the marine divers have their own marina in Primorsk.

Equipped with fast assault boats like the Raptor, they have posed a threat to Polish coastal infrastructure for years. Experts pointed out that Poland lacked the appropriate equipment to effectively counter potential attacks by small sabotage groups.

The situation changed somewhat in 2023 when an agreement was signed for a new Griffon hovercraft for the Maritime Border Guard. Units SG-413 and SG-414 were ceremonially commissioned on 11 December 2024 at a ceremony organised in Stara Pasłęka.