“It starts, Jacobsen explains, with a radar screen blip, touching off a chaotic countdown in which the president—and their uppermost military advisers—must decide if, when, where, and how to retaliate. The federal choreography from there is profound, demanding operational perfection from staff in countless agencies tasked with missile interception, international diplomacy, disaster response, and continuity of government—all in a haze of incomplete information. “Nuclear war,” as she argues, “robs man of reason.”