The Baltic is becoming a battleground between NATO and Russia
Russian spooks may also be using some of the ships for operations above sea-level.
Compared with Russia’s hulking nuclear-powered submarines, Sweden’s a26, at just 66 meters long, is a compact model. But what the Saab-built sub lacks in size it makes up for in stealth and surveillance abilities. A portal built into its bow lets it deploy underwater drones, sensors or divers onto the seabed. For the Baltic Sea’s murky waters, and for the cold war unfolding beneath them, the a26 delivers the most bang for the buck. That at least was the conclusion Poland’s government reached on November 26th, when it decided to buy three of the vessels for an estimated $2.8bn.
For countries like Poland, having eyes on and under the Baltic is a pressing matter of national security. The sea teems with telecoms and energy infrastructure. A natural-gas pipeline, the Balticconnector, links Finland and Estonia. Another, Baltic Pipe, transports gas from Norway to Poland. Communications and power cables line the seabed. Earlier this year Estonia, Latvia and Lithuania unplugged their power systems from Russia’s grid; of the four links that connect them to the European one, three are underwater. Above the surface, hundreds of wind turbines stand off the coasts of Denmark and Germany, and new ones are rising off Poland’s. The Baltic’s shores host ten lng terminals, with two more under construction.
On paper, nato’s presence in the Baltic has never been stronger. Of the sea’s nine littoral states, all but Russia belong to the alliance. But although nato has a clear edge in the Baltic when it comes to conventional naval power, Russia has the means to wreak havoc. Since 2023 there have been at least 11 suspected acts of sabotage to Baltic Sea infrastructure, many of them linked to Russia’s shadow fleet, the network of tankers the country uses to bypass Western sanctions. The worst were ruptures of the Balticconnector and of a power cable linking Finland and Estonia, probably caused by ships dragging their anchors along the sea floor. Both took months to repair.
Russian spooks may also be using some of the ships for operations above sea-level. In September drones that seem to have been launched from ships linked to Russia were spotted over Danish airports. Similar incidents have since taken place in France and Germany.
Hybrid attacks allow Russia to deny involvement, test nato’s mutual-defence clause and gauge each member’s appetite for confrontation. But Vladimir Putin’s regime is also starting to do things in the open. In early October Denmark’s defence intelligence service revealed that Russian warships had pointed their weapons at Danish navy ships and helicopters, and sailed in the direction of Danish vessels, simulating a collision.
Russia will soon have more targets to choose from. Germany, Denmark, Sweden and Finland are building new Baltic Sea wind farms. Poland is even more exposed. It relies on the Baltic’s pipelines and ports for nearly half of its energy imports, and that dependence is growing. By 2040 the country may invest well over $100bn in offshore wind farms and new lng terminals. Poland’s first nuclear power plant, expected to open by 2036, will be less than 2km inshore.
Many of these projects were thought up when the threat from Russia seemed abstract. Now governments are scrambling to protect them—a tough challenge. Radars and satellites can monitor the skies and track ships, even when they turn off their transponders. But tracking what happens below the surface is much harder, which makes the seabed ideal terrain for hybrid attacks.
Much existing surveillance technology, which relies on sonar, is poorly suited to the Baltic. The shallow and cluttered seabed creates acoustic noise, maritime traffic masks underwater activity and sharp changes in salinity distort sound waves. New solutions will plug some of the gaps, including hydro-acoustic sensors, submarines like the a26 and unmanned underwater vehicles (uuvs). But developing an integrated surveillance system, a key nato objective for the Baltic, will take years.
Projects like the a26 face long delays. Sweden’s navy had planned to take delivery of the first of two submarines it ordered from Saab in 2022. That has been pushed back to 2031. (The need to upgrade the shipyard where the subs are built is said to be one of the reasons for the delay.) Poland, whose navy fields only one creaky Soviet-era submarine, will need to wait until the 2030s for the three a26s it has ordered. Meanwhile, Britain’s main military-intelligence agency recently concluded that Russia is modernising its fleet to target undersea cables and pipelines.
So even with new technology to improve monitoring, detection and repairs, nato needs to do more to show Russia that its hybrid attacks will not go unpunished. The response so far has been largely reactive. Under nato’s Baltic Sentry operation, launched in early 2025, the alliance has stepped up patrols on the Baltic. But although nato vessels can hail commercial ships to check whether they have valid registration, under international law their crews are not allowed to board or inspect them.
Some countries have floated more drastic measures. In the wake of the drone incursions over Denmark, Ukraine’s president, Volodymyr Zelensky, suggested closing the Baltic to shadow-fleet tankers. Estonia’s defence minister, Hanno Pevkur, had proposed doing so months earlier.
Such a blockade, however, would almost certainly violate international law. The un Convention on the Law of the Sea guarantees ships, even sanctioned ones, the right to pass through international straits as long as they do not threaten force or violate safety rules. Russia, which uses the Baltic for 60% of its seaborne crude oil exports, would probably consider the closing of Danish straits to shadow-fleet tankers an act of war. A more prudent response would be to deny access to ships that do not meet technical standards, says Jacek Siewiera, former head of Poland’s national security council.
That approach is gaining traction. In October Denmark stepped up controls of tankers at the Skagen anchorage, which connects the North Sea with the Baltic. Poland, meanwhile, is giving its naval deterrent more teeth. A bill passed by the country’s parliament in November allows the navy to use force to protect critical infrastructure, even outside Poland’s territorial waters.
Protection is expensive, but not compared to dealing with attacks. A recent study by rand, a think-tank, put the daily cost of repairing an undersea telecoms cable at €24m ($28m), an oil pipeline at €36m and a gas pipeline at €75m. Such repairs usually take months. Lost energy supplies and connectivity compound the damage. Enough such provocations, and a submarine or two starts to look like a bargain.
Compared with Russia’s hulking nuclear-powered submarines, Sweden’s a26, at just 66 meters long, is a compact model. But what the Saab-built sub lacks in size it makes up for in stealth and surveillance abilities. A portal built into its bow lets it deploy underwater drones, sensors or divers onto the seabed. For the Baltic Sea’s murky waters, and for the cold war unfolding beneath them, the a26 delivers the most bang for the buck. That at least was the conclusion Poland’s government reached on November 26th, when it decided to buy three of the vessels for an estimated $2.8bn.
For countries like Poland, having eyes on and under the Baltic is a pressing matter of national security. The sea teems with telecoms and energy infrastructure. A natural-gas pipeline, the Balticconnector, links Finland and Estonia. Another, Baltic Pipe, transports gas from Norway to Poland. Communications and power cables line the seabed. Earlier this year Estonia, Latvia and Lithuania unplugged their power systems from Russia’s grid; of the four links that connect them to the European one, three are underwater. Above the surface, hundreds of wind turbines stand off the coasts of Denmark and Germany, and new ones are rising off Poland’s. The Baltic’s shores host ten lng terminals, with two more under construction.
On paper, nato’s presence in the Baltic has never been stronger. Of the sea’s nine littoral states, all but Russia belong to the alliance. But although nato has a clear edge in the Baltic when it comes to conventional naval power, Russia has the means to wreak havoc. Since 2023 there have been at least 11 suspected acts of sabotage to Baltic Sea infrastructure, many of them linked to Russia’s shadow fleet, the network of tankers the country uses to bypass Western sanctions. The worst were ruptures of the Balticconnector and of a power cable linking Finland and Estonia, probably caused by ships dragging their anchors along the sea floor. Both took months to repair.
Russian spooks may also be using some of the ships for operations above sea-level. In September drones that seem to have been launched from ships linked to Russia were spotted over Danish airports. Similar incidents have since taken place in France and Germany.
Hybrid attacks allow Russia to deny involvement, test nato’s mutual-defence clause and gauge each member’s appetite for confrontation. But Vladimir Putin’s regime is also starting to do things in the open. In early October Denmark’s defence intelligence service revealed that Russian warships had pointed their weapons at Danish navy ships and helicopters, and sailed in the direction of Danish vessels, simulating a collision.
Russia will soon have more targets to choose from. Germany, Denmark, Sweden and Finland are building new Baltic Sea wind farms. Poland is even more exposed. It relies on the Baltic’s pipelines and ports for nearly half of its energy imports, and that dependence is growing. By 2040 the country may invest well over $100bn in offshore wind farms and new lng terminals. Poland’s first nuclear power plant, expected to open by 2036, will be less than 2km inshore.
Many of these projects were thought up when the threat from Russia seemed abstract. Now governments are scrambling to protect them—a tough challenge. Radars and satellites can monitor the skies and track ships, even when they turn off their transponders. But tracking what happens below the surface is much harder, which makes the seabed ideal terrain for hybrid attacks.
Much existing surveillance technology, which relies on sonar, is poorly suited to the Baltic. The shallow and cluttered seabed creates acoustic noise, maritime traffic masks underwater activity and sharp changes in salinity distort sound waves. New solutions will plug some of the gaps, including hydro-acoustic sensors, submarines like the a26 and unmanned underwater vehicles (uuvs). But developing an integrated surveillance system, a key nato objective for the Baltic, will take years.
Projects like the a26 face long delays. Sweden’s navy had planned to take delivery of the first of two submarines it ordered from Saab in 2022. That has been pushed back to 2031. (The need to upgrade the shipyard where the subs are built is said to be one of the reasons for the delay.) Poland, whose navy fields only one creaky Soviet-era submarine, will need to wait until the 2030s for the three a26s it has ordered. Meanwhile, Britain’s main military-intelligence agency recently concluded that Russia is modernising its fleet to target undersea cables and pipelines.
So even with new technology to improve monitoring, detection and repairs, nato needs to do more to show Russia that its hybrid attacks will not go unpunished. The response so far has been largely reactive. Under nato’s Baltic Sentry operation, launched in early 2025, the alliance has stepped up patrols on the Baltic. But although nato vessels can hail commercial ships to check whether they have valid registration, under international law their crews are not allowed to board or inspect them.
Some countries have floated more drastic measures. In the wake of the drone incursions over Denmark, Ukraine’s president, Volodymyr Zelensky, suggested closing the Baltic to shadow-fleet tankers. Estonia’s defence minister, Hanno Pevkur, had proposed doing so months earlier.
Such a blockade, however, would almost certainly violate international law. The un Convention on the Law of the Sea guarantees ships, even sanctioned ones, the right to pass through international straits as long as they do not threaten force or violate safety rules. Russia, which uses the Baltic for 60% of its seaborne crude oil exports, would probably consider the closing of Danish straits to shadow-fleet tankers an act of war. A more prudent response would be to deny access to ships that do not meet technical standards, says Jacek Siewiera, former head of Poland’s national security council.
That approach is gaining traction. In October Denmark stepped up controls of tankers at the Skagen anchorage, which connects the North Sea with the Baltic. Poland, meanwhile, is giving its naval deterrent more teeth. A bill passed by the country’s parliament in November allows the navy to use force to protect critical infrastructure, even outside Poland’s territorial waters.
Protection is expensive, but not compared to dealing with attacks. A recent study by rand, a think-tank, put the daily cost of repairing an undersea telecoms cable at €24m ($28m), an oil pipeline at €36m and a gas pipeline at €75m. Such repairs usually take months. Lost energy supplies and connectivity compound the damage. Enough such provocations, and a submarine or two starts to look like a bargain.
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