Drell was an undergraduate at Princeton University when Hiroshima and Nagasaki were destroyed. Given all the close calls and mistakes in the seventy-one years since then, he considered it a miracle that no other cities have been destroyed by a nuclear weapon—“it is so far beyond my normal optimism.” The prospect of a new cold war—and the return of military strategies that advocate using nuclear weapons on the battlefield—deeply unnerved him. Once the first nuclear weapon detonates, nothing might prevent the conflict from spiralling out of control. “We have no experience in stopping a nuclear war,” he said.

During the recent Presidential campaign, the emotional stability of the Commander-in-Chief became an issue, with some arguing that a calm disposition might mean the difference between peace on Earth and a nuclear apocalypse. The President of the United States has the sole power to order the use of nuclear weapons, without any legal obligation to consult members of Congress or the Joint Chiefs of Staff. Ideally, the President would never be short-tempered, impulsive, or clinically depressed. But the mood of the Commander-in-Chief may be irrelevant in a nuclear crisis, given the current technological constraints. Can any human being reliably make the correct decision, within six minutes, with hundreds of millions of lives at stake?

Donald Trump and Vladimir Putin confront a stark choice: begin another nuclear-arms race or reduce the threat of nuclear war. Trump now has a unique opportunity to pursue the latter, despite the bluster and posturing on both sides. His admiration for Putin, regardless of its merits, could provide the basis for meaningful discussions about how to minimize nuclear risks. Last year, General James Mattis, the former Marine chosen by Trump to serve as Secretary of Defense, called for a fundamental reappraisal of American nuclear strategy and questioned the need for land-based missiles. During Senate testimony, Mattis suggested that getting rid of such missiles would “reduce the false-alarm danger.” Contrary to expectations, Republican Presidents have proved much more successful than their Democratic counterparts at nuclear disarmament. President George H. W. Bush cut the size of the American arsenal in half, as did his son, President George W. Bush. And President Ronald Reagan came close to negotiating a treaty with the Soviet Union that would have completely abolished nuclear weapons.