As NATO allies accuse Russia of waging hybrid warfare, the United States joins war drills in Sweden aimed at disrupting sabotage.

Stockholm — A growing number of Mysterious drone sightings near airports and military bases has fueled concern in Europe over Russia’s alleged incursions into NATO airspace, with some US allies already saying the continent is in a gray zone between peace and war – accusing Moscow of escalating “hybrid warfare”.

NATO, the North Atlantic Treaty Organization, is arguably the United States’ most important alliance, having existed for more than 75 years. In Sweden, CBS News saw this alliance in action this week – in waters contested by Russia.

Our team observed an enemy submarine preparing for a covert espionage and sabotage mission in the Baltic Sea against America’s NATO allies in Northern Europe.

It was simply a military exercise launched from the port of Stockholm, and a German submarine played the role of an anonymous enemy hunted by NATO forces across the Baltic Sea.

American forces participated, flying over the operations aboard spy planes.

“NATO is a defensive alliance,” Commander Arlo Abrahamson, a U.S. naval officer and spokesman for NATO’s maritime headquarters who is closely monitoring Russia’s military buildup in the Baltic, told CBS News. “Potential threats from adversaries in this region are interconnected throughout the world.”

Abrahamson said that if Northern Europe were drawn into conflict, it would also have a negative impact on the United States.

Several US NATO allies share a Baltic coast with Russia. In recent years, Russia has been suspected of commit multiple acts of sabotage – including the damaging underwater data cables that form the backbone of the global Internet.

Some believe Russia is using the Baltic Sea as a testing ground to gauge the damage it could do to the Western economy if it ever went to war with NATO. Undersea cables carry trillions of dollars of financial transactions every day.

The country leading the exercises this week, Sweden, gave CBS News rare access to one of its stealth warships, the HMS Helsingborg, as it hunted the pseudo-enemy submarine.

For more than 200 years, Sweden maintained a policy of military non-alignment, but last year, following Russia’s invasion of Ukraine in 2022, it became NATO’s newest member.

“We face the Russians every day, sharing the same duck pond, so to speak,” submarine flotilla commander Paula Wallenburg of the Swedish Navy told CBS News.

She echoed recent statements by Lithuanian officials accusation that Russia is engaged in some sort of hybrid war with allegations of airspace violations and acts of sabotage.

“We are not at peace, but not at war,” she said. “We’re somewhere in between.”

Wallenburg agreed that current circumstances seem “pretty close” to those seen during the Cold War, when the nuclear-armed United States and then the Soviet Union tested each other’s resolve in a high-stakes confrontation that never quite escalated into a full-scale war.

“It’s a very serious situation in terms of security here in this area,” she said.

The Kremlin has already declared that Russia is at war with NATO, due to the alliance’s support for Ukraine.

America’s NATO allies around the Baltic Sea, including Sweden, Finland, Poland and Germany, have all decided to significantly increase their national military spending and strengthen their defense.