The impact of the use of a nuclear device in Ukraine will depend on the details. Like any large-scale industrial army, the Ukrainian Armed Forces have obvious pressure points that would be vulnerable to nuclear attack. These include logistical centers, command and communications nodes, and concentrations of front-line forces. During the Cold War the Soviet Union expected to use tactical nuclear weapons against NATO (and expected that NATO would use them in return) and it is therefore likely that the Russian armed forces have workable theories as to how they might best use tactical nukes to inflict damage on Ukraine’s...