India and Pakistan have seemingly pulled back from the brink again. But so much was new about the nuclear-armed enemies’ chaotic four-day clash, and so many of the underlying accelerants remain volatile, that there’s little to suggest that the truce represents any return to old patterns of restraint. A new generation of military technology fueled a dizzying aerial escalation. Waves of airstrikes and antiaircraft volleys with modern weapons set the stage. Soon they were joined by weaponized drones en masse for the first time along the old Line of Control in Kashmir — hundreds of them in the sky, probing...