Hybrid attacks in the Baltic Sea. The Economist explains how NATO is countering Russia

NATO countries are stepping up their presence in the Baltic Sea to protect their own infrastructure amid Russian activity in the region. This is discussed in the article The Economist.

"On paper, NATO's presence in the Baltic Sea has never been stronger. Of the nine littoral countries in the Baltic Sea, all but Russia are members of the Alliance. But while NATO has a clear advantage in the Baltic Sea in terms of conventional naval power, Russia has the means to wreak havoc," the article notes.

Since 2023, at least 11 alleged acts of sabotage against the Baltic Sea infrastructure have been recorded, many of which are linked to the Russian "shadow fleet."

Russian intelligence services may use some of these ships for operations. In September, drones were spotted flying over airports in Denmark, allegedly launched from ships linked to Russia. Similar incidents have since occurred in France and Germany.

Hybrid attacks allow Russia to deny its involvement, test NATO's mutual defense clause, and assess each member's readiness for confrontation. But the regime of the Russian dictator Vladimir Putin is also beginning to act openly. In early October, the Danish Defense Intelligence Agency reported that Russian warships had pointed their weapons at Danish Navy ships and helicopters and moved in their direction, simulating a clash.

The publication writes that the Allies have numerous infrastructure in the Baltic Sea. Many of these projects were conceived when the threat from Russia seemed abstract.

Now governments are trying to protect the infrastructure, which is a difficult task. Radars and satellites can monitor the sky and track ships even when they have turned off their transponders. But tracking what's happening on the seabed is much more difficult, making it ideal terrain for hybrid attacks.

Shallow waters and cluttered seabeds create acoustic noise, marine traffic masks underwater activity, and sudden changes in salinity distort sound waves. New solutions will fill some of the gaps, including hydroacoustic sensors, submarines such as Sweden's A26, and unmanned underwater vehicles. But the development of an integrated surveillance system, NATO's main task for the Baltic Sea, will take years.

The newspaper writes that compared to bulky Russian nuclear submarines, the A26, which is only 66 meters long, is a compact model. In November, Poland bought three of these vessels for a total of $2.8 billion. However, Poland, whose fleet has only one malfunctioning Soviet-era submarine, will have to wait until the 2030s.

Thus, even with new technologies that improve monitoring, detection, and repair, NATO needs to do more to show Russia that its hybrid attacks will not go unpunished.

Response measures have so far been largely reactive. As part of NATO's Operation Baltic Watch, launched in early 2025, the Alliance has stepped up patrols of the Baltic Sea. But while NATO ships can contact commercial vessels to check that they have valid registration, under international law, their crews are not allowed to board or inspect them.

Against this backdrop, there have been calls to close the Baltic Sea to shadow fleet tankers. However, such a blockade would almost certainly violate international law. The United Nations Convention on the Law of the Sea guarantees ships, even those under sanctions, the right to pass through international straits if they do not threaten the use of force or violate security rules.

Russia, which uses the Baltic Sea for 60% of its crude oil exports by sea, is likely to view the closure of the straits to shadow fleet tankers as an act of war.

Another way to close the sea is to deny access to ships that do not meet technical standards. This approach is gaining popularity.

• On December 6, it was reported that Swedish navy "almost every week" encounters Russian submarines in the Baltic Sea.
• Subsequently, Sweden confirmed that Russia began to provide military protection for "shadow fleet" tankers – warships patrol certain areas of the Baltic Sea, and armed guards have appeared on board oil ships.