“OUR COMMITMENT to defend…every inch of Allied territory at all times”, declared NATO at its summit last year, “is iron-clad.” That may be true on the ground. But in recent weeks it has seemed shakier in the air. First came a wave of Russian drones, into Poland, on September 9th. Then a trio of Russian MiG-31 fighter jets entered Estonian airspace on September 19th, traversing it for 12 minutes. Days later a wave of mysterious drones shut down Denmark’s main airport and appeared over Oslo. As Donald Trump steps back from Europe and efforts to end the war in Ukraine, Vladimir Putin appears to be turning the screws on the continent.