This month marks the fiftieth anniversary of Stanley Kubrick’s black comedy about nuclear weapons, “Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb.” ... Half a century after Kubrick’s mad general, Jack D. Ripper, launched a nuclear strike on the Soviets to defend the purity of “our precious bodily fluids” from Communist subversion, we now know that American officers did indeed have the ability to start a Third World War on their own. And despite the introduction of rigorous safeguards in the years since then, the risk of an accidental or unauthorized nuclear detonation hasn’t been completely eliminated.

The command and control of nuclear weapons has long been plagued by an “always/never” dilemma. The administrative and technological systems that are necessary to insure that nuclear weapons are always available for use in wartime may be quite different from those necessary to guarantee that such weapons can never be used, without proper authorization, in peacetime. During the nineteen-fifties and sixties, the “always” in American war planning was given far greater precedence than the “never.” Through two terms in office, beginning in 1953, President Dwight D. Eisenhower struggled with this dilemma. He wanted to retain Presidential control of nuclear weapons while defending America and its allies from attack. But, in a crisis, those two goals might prove contradictory, raising all sorts of difficult questions. What if Soviet bombers were en route to the United States but the President somehow couldn’t be reached? What if Soviet tanks were rolling into West Germany but a communications breakdown prevented NATO officers from contacting the White House? What if the President were killed during a surprise attack on Washington, D.C., along with the rest of the nation’s civilian leadership? Who would order a nuclear retaliation then?

With great reluctance, Eisenhower agreed to let American officers use their nuclear weapons, in an emergency, if there were no time or no means to contact the President. Air Force pilots were allowed to fire their nuclear anti-aircraft rockets to shoot down Soviet bombers heading toward the United States. And about half a dozen high-level American commanders were allowed to use far more powerful nuclear weapons, without contacting the White House first, when their forces were under attack and “the urgency of time and circumstances clearly does not permit a specific decision by the President, or other person empowered to act in his stead.” Eisenhower worried that providing that sort of authorization in advance could make it possible for someone to do “something foolish down the chain of command” and start an all-out nuclear war. But the alternative—allowing an attack on the United States to go unanswered or NATO forces to be overrun—seemed a lot worse. Aware that his decision might create public unease about who really controlled America’s nuclear arsenal, Eisenhower insisted that his delegation of Presidential authority be kept secret. At a meeting with the Joint Chiefs of Staff, he confessed to being “very fearful of having written papers on this matter."...