Daniel Ellsberg became a household name—and, according to Henry Kissinger, “the most dangerous man in America”—in 1971, when he leaked the Pentagon Papers, a massive study of how the U. S. blundered in Vietnam that Ellsberg himself had helped compile as a RAND Corporation analyst. But before he was a disillusioned expert on Vietnam, he was a disillusioned expert on America’s “command and control” structure for nuclear war. He tells the story in his new book, The Doomsday Machine: Confessions of a Nuclear War Planner (Bloomsbury), a groundbreaking and nightmare-inducing account of how the whole mad system works. Esquire spoke to him this fall, just after Donald Trump began tweeting threats to North Korea’s Kim Jong Un and just before Senator Bob Corker warned that the president might be leading us toward World War III.

Rick Perlstein: Historians have wondered why Richard Nixon and Henry Kissinger were so panicked by the release of the Pentagon Papers, since they described policies from before Nixon came to power and obviously didn’t implicate them. One hypothesis was that they were terrified that you had access to the Single Integrated Operational Plan (SIOP) for nuclear war.

Daniel Ellsberg: No, they were worried that I knew about their nuclear threats. As the tapes show, Nixon was talking about the possible use of nuclear weapons against North Vietnam: “No, no, no, no, I’ve got to use nuclear weapons. Got that, Henry?” Then Kissinger says, “Oh, I think that would just be too much.” “Nuclear weapons bother you, Henry? I just want you to think big, for Christ’s sake.”

RP: You write that once you learned about these first-strike plans for North Vietnam, you were confronted “with a challenging question: If I hadn’t known about this, what else didn’t I know?” Can you talk about what you ended up learning—how American military policy has always been based on the assumption of an American first strike, not a Soviet first strike—and why that was?

DE: The U. S. had a monopoly on nuclear weapons from ’45 to ’49. Our war plans were initially nothing but first-strike plans. That term would not have even been used. It’d be like calling the Great War the First World War in the ’20s. When the Soviets got nuclear weapons in 1949, the plans pretty much continued. ...