In 2010, the chairman of the Joint Chiefs of Staff, Admiral Michael Mullen, warned that American defense institutions were no longer minting nuclear strategists. “We don’t have anybody in our military that does that anymore,” Mullen said.

I saw this firsthand at the Naval War College, a graduate school for mid-level and senior U.S. military officers, where I taught for more than 25 years. Nuclear issues fell out of the curriculum almost immediately after the Cold War ended. I remember an Air Force major coming up to me after class and telling me he’d never heard of “mutual assured destruction”—the concept that underlies nuclear deterrence—until my lecture that day.

Voters no longer cared either. During the Cold War, regardless of what other issues might be raised, every presidential election was shadowed by worry over whose finger would be on “the button.” In 1983, Reagan—hardly a detail-oriented president or master policy wonk—asked for an uninterrupted half hour of television during prime time to discuss his defense budget and his plans for a national missile-defense system, replete with charts and graphs. Millions of Americans watched. But in 2015, when Donald Trump was asked during the Republican Party primary debates about U.S. nuclear forces, he could only say, “With nuclear, the power, the devastation is very important to me.” Such an answer would once have been disqualifying for any candidate. This time, millions of Americans shrugged.