With wars of aggression in Europe and the Middle East, looming crises in Asia and mass demonstrations in support of violent terrorism throughout the West, Paul Gigot is right to suggest that “we face an array of adversaries more formidable than at any time since World War II, and we aren’t prepared for the moment” (“Isolationism Makes a Perilous Moment More So,” op-ed, Nov. 11). American deterrence is collapsing, the thin veneer of civilization hangs in the balance, and the Biden administration’s limping, confused response has only made it worse.

Yet this is no time to lose faith, retreat and succumb to the siren song of American decline. As a young physics professor on leave from the University of Berlin wrote when visiting America in 1931: “The people of this country must realize they have a great responsibility in the sphere of international politics. The part of passive spectator is unworthy of this country and is bound in the end to lead to disaster all around.”