Jérôme Denariez examines the escalation of tensions in the Baltic Sea between Russia and NATO, which manifests itself through a hybrid confrontation that falls below the threshold of an open conventional conflict. He highlights the difficulty Western democracies face in quickly attributing responsibility for incidents—such as the sabotage of undersea cables or the use of ghost fleets—due to the uncertainty perpetuated by Moscow. Faced with this climate of insecurity, the coastal countries most at risk are urgently adapting their active defense doctrines and maritime surveillance capabilities. The crucial challenge now lies in the ability of European allies to shorten the time required for analysis and political decision-making in order to counter these threats before they escalate.