One of the supposed paradoxes of our day is that the past quarter-century has been a golden age of nuclear disarmament. From a mid-1980s peak of more than 70,000 warheads world-wide, we’re down to fewer than 15,000. South Africa, Ukraine, Kazakhstan and Belarus all voluntarily abandoned their nuclear weapons at the end of the Cold War.

Yet none of this has made the free world safer. Ukrainians can rue their 1994 decision to abandon their nuclear arsenal as the reason Vladimir Putin felt free to invade in 2014. The United States withdrew its tactical nuclear weapons from South Korea in 1991 as a peace-building measure. So much for that. Seoul, Taipei and Tokyo are very quietly mulling their nuclear options as doubts about the reliability of American guarantees grow. So is Saudi Arabia in the face of Iran’s nuclear ambitions, or at least it was during the previous administration.