With its powerful camera, the French Navy surveillance plane scouring the Baltic Sea zoomed in on a cargo ship plowing the waters below — closer, closer and closer still until the camera operator could make out details on the vessel's front deck and smoke pouring from its chimney.

This heightened surveillance, both in the air and at sea, signals Nato’s intensified efforts to protect underwater infrastructure in the Baltic. The alliance is responding to a concerning rise in incidents involving damage to vital energy and data cables and pipelines.