“As president, Eisenhower would twice be presented with recommendations from his National Security Council and the Joint Chiefs of Staff that the bomb be used; first, in Vietnam to protect the French at Dien Bien Phu, then against China at the time of the Formosa Strait crisis. Both times Eisenhower rejected the recommendations. As a former supreme commander, Eisenhower had the confidence to do so, where other presidents might not have. And by rejecting the use of the bomb, there is no question that Eisenhower raised the threshold at which atomic weaponry could be employed — a legacy we continue to enjoy.”

But for how long? The nonproliferation regime has been remarkably successful. During the 1960 presidential campaign, John Kennedy cited “indications” that by 1964 there would be “10, 15 or 20” nuclear powers. As president, he said that by 1975 there might be 20. Now, however, North Korea, the ninth, might be joined by Japan, South Korea and Taiwan, among others, unless U.S. leadership produces, regarding North Korea, conspicuously credible deterrence. The reservoir of presidential credibility is not brimful.