When Sweden and Finland applied to join NATO in May 2022, supporters hailed the moment as the Baltic Sea’s transformation into “a NATO lake.” Since then, confrontations with Russia and interference with undersea infrastructure have made those waters anything but placid.

Sweden, Finland, and their NATO allies now face a difficult balancing act. They are seeking ways to counter increasingly aggressive Russian behavior without driving tensions to an even more dangerous level.

The Baltic has long been a theater for hybrid warfare, including sabotage, cyberattacks, disinformation, and territorial violations that remain below the threshold of open war and can be difficult to attribute. That activity has increased since Russia invaded Ukraine in 2022.

Dutch military intelligence warned earlier this year of “a real risk of unintended and therefore difficult-to-control escalation.” The warning captures the central danger facing NATO members as suspicious incidents, military encounters, and infrastructure damage accumulate across the region.

The September 2022 attack on the Nord Stream pipeline was among the most prominent cases. Other pipelines and cables in the Baltic have since been damaged in incidents that Western officials often describe as sabotage, while NATO allies have also faced frequent GPS jamming.

Russian aircraft have violated allied airspace, and drones have entered sensitive locations such as military bases and airports. Russia consistently denies responsibility, but NATO leaders connect those actions to Moscow’s efforts to undermine neighboring countries and retaliate for their support of Ukraine.

Denmark’s Defense Intelligence Service said in a September assessment that “Russia has intensified its use of sabotage, destructive cyber attacks and is attacking targets in Europe with drones.” The assessment added a blunt conclusion: “The hybrid war is escalating.”

Russia has also taken a more active role in protecting vessels from its so called “shadow fleet,” which it uses to avoid sanctions. Russian warships have escorted those vessels through the Baltic, producing confrontations with NATO forces operating in the region.

The Danish assessment said, “Russian forces are increasingly acting aggressively towards NATO military units in the Baltic Sea region.” It identified a Sept. 14 incident in which a Russian frigate near Denmark’s coast fired flares at a Danish military helicopter as the most recent and most serious example.

Maj. Gen. Peter Boysen, chief of the Danish army, addressed the dilemma during the Association of the U.S. Army annual conference in Washington, D.C., in mid October. “It’s a very difficult question, because you don’t want to escalate,” Boysen said.

Boysen said Denmark would seek to reduce tensions after an incident such as the flare encounter, while still signaling that the conduct was unacceptable. He warned that repeated aggressive behavior cannot be allowed to redefine what allies accept as normal in the Baltic.

“What we don’t want to do is to move ‘normal’ to a new intensity level,” Boysen said. “Normal needs to be decreased, and that’s a very, very difficult question.”

Lt. Gen. Kari Nisula, the Finnish Defense Forces’ deputy chief of staff for operations, said Russia’s wartime posture and concern about Ukraine’s long range strikes further complicate escalation control. Russian forces in the Baltic employ air defense and force protection measures because they fear their ships could be struck, he said.

NATO has responded by increasing vigilance and cooperation. Germany established Commander Task Force Baltic in October 2024 to coordinate naval activity and provide allies with current maritime situational awareness.

Around the same period, NATO’s Allied Command Transformation created Task Force X-Baltic to speed the use of uncrewed systems and integrate AI for protecting undersea infrastructure. NATO then began Baltic Sentry in January 2025 as an operation intended to strengthen the alliance’s regional presence and responsiveness.

Sweden and Finland are also expanding cooperation to monitor and defend their territory. Following drone incursions in Finland and other NATO countries, Stockholm authorized its military this summer to help Helsinki maintain “territorial surveillance and territorial integrity,” according to Maj. Gen. Johan Pekkari, commander of the Swedish army.

Pekkari said Sweden can place air assets under Finland’s air operational command for sorties against drones. Sweden could eventually provide systems designed to counter drones as another part of that cooperation.

Boysen argued that detection and identification are essential alongside the ability to project power. “Being able to put light on the adversary, to tell the adversary we know what you are doing — I think that is the way to de-escalate it,” he said.

NATO members remain divided over whether emphasizing Russia’s actions spreads fear or provides transparency necessary for sustaining public support. Finland’s ambassador to the U.S., Leena-Kaisa Mikkola, said Finland “might have to expect even more hybrid attacks in the near future,” while quoting her country’s defense minister describing the Baltic situation as “quite lively.”