Ranking some weapons as “low-yield” based on their destructive energy always depended on a distinction that reality made meaningless (once damage from radioactivity and atmospheric fallout was taken into account along with the unlikelihood that only one such weapon would be used). In fact, the elimination of tactical nukes represented a hard-boiled confrontation with the iron law of escalation, another commander’s insight — that any use of such a weapon against a similarly armed adversary would likely ignite an inevitable chain of nuclear escalation whose end point was barely imaginable. One side was never going to take a hit without responding in kind, launching a process that could rapidly spiral toward an apocalyptic exchange. “Limited nuclear war,” in other words, was a fool’s fantasy and gradually came to be universally acknowledged as such. No longer, unfortunately.