When did Western statecraft lose its fear of the unknown?

As Western leaders departed the G7 summit in Évian talking of a “strategic awakening in support of Ukraine,” the night sky over Moscow was illuminated by the fires of a burning oil refinery just nine miles from the Kremlin. This unprecedented Ukrainian drone strike on Russian territory was met in Western capitals with quiet endorsement rather than anxiety. During the tensest moments of the Cold War, Western statecraft was anchored by a healthy fear of the unknown. Today, that prudence has been replaced by confidence that conflict can be precisely managed. When Franklin D. Roosevelt famously declared that "the only...