Imagine a rapidly escalating conflict between Russian and NATO forces. Compensating for Russia’s perceived conventional inferiority, Russian commanders execute a limited nuclear strike — a small number of low-yield weapons intended to change conditions on the battlefield. The U.S. president, in turn, authorizes a limited nuclear response just before being evacuated from the White House. While rushing toward their helicopter, he or she wonders what Russia’s next move will be and hopes they will not have to authorize additional nuclear strikes. The problem is they may have unintentionally done so already.