As the 1973 Yom Kippur war between Israel and neighboring Arab states intensified, I was in an underground missile launch center in Montana with a crewmate when we received an emergency message to prepare for nuclear war with the Soviet Union. We trusted the president to defuse the crisis and avert a nuclear war. Dwight D. Eisenhower recoiled at the concept of nuclear overkill, where far more people are killed than necessary to defeat an enemy. Richard M. Nixon (president during the 1973 Arab-Israeli war) ... worried about the way war plans lightly tossed about millions of deaths." Ronald Reagan, for all his thunder about the Soviet Union being "an evil empire" and joking that "we begin bombing in five minutes," was privately averse to nuclear weapons. Donald J. Trump is of a radically different ilk and temperament from past presidents. In 1973, as it turned out, President Nixon was not in charge when the order came down to prepare for nuclear conflict. Under stress from the Watergate scandal, he had retired for the evening, drunk. His unelected advisers, led by the national security adviser, Henry A. Kissinger, and Defense Secretary James R. Schlesinger, ran the show that night. Our trust in the president was misplaced. He was not even awake when my crewmate and I saddled up for nuclear war. The president had lost personal control of the situation. But upon reflection, it would have been far scarier if a cocksure Mr. Trump, consulting no one but himself, had been there calling the shots.