When he last spoke with Reason in 1973, Daniel Ellsberg was on trial for leaking the Pentagon Papers. The Harvard-educated military analyst at the RAND Corporation had long wrestled with many of the moral quandaries of war, but was a consummate Washington insider up until the moment he decided to release a classified Department of Defense study of the Vietnam War, with its damning proof that President Lyndon Johnson had misled Congress and the public about the conflict.

While it looked like Ellsberg might spend the rest of his life behind bars, he was saved—ironically—by Richard Nixon's paranoid dealings, which included sending goons to break into Ellsberg's former psychiatrist's office and allegedly plotting to have him killed.

If the original leaking plan had gone Ellsberg's way, he suspects he might be in prison still. As he relates in his new book, Doomsday Machine: Confessions of a Nuclear War Planner (Bloomsbury), along with the now-familiar thousands of pages on Vietnam, he had unprecedented civilian access to nuclear planning documents in the Eisenhower and Kennedy years. He swiped and copied them as well. Unfortunately, Ellsberg gave the nuclear documents to his brother, who buried them for safekeeping until the Pentagon Papers trial was over. A hurricane collapsed the hill where they were hidden, and they were lost to history. Ellsberg has had 45 years to wonder what would have happened if they hadn't been, and more than 60 years to be unnerved by the recklessness, poor planning, and misinformation rampant in an area of policy with the highest possible stakes.

Today, Ellsberg is the 86-year-old elder statesmen of whistleblowing. He calls Edward Snowden "a hero of mine." In return, Snowden has said he was following in Ellsberg's footsteps when he leaked his own cache of secret government documents in 2013.

Reason spoke with Ellsberg by phone in October about his new book, his belief that nobody needs more nuclear weapons than Kim Jong Un has, and why the Cold War's apocalyptic threats still hang over us.

Reason: Do you still get people calling you a traitor, and do you anticipate getting more of that on Twitter, now that you have a presence there?

Daniel Ellsberg: For decades I used to say that being called "traitor" is something you never get used to. But the truth is, for humans, you get used to anything. After 40 years, it doesn't get a big rise out of me anymore.

It did very much at first. As a person whose identification was patriotism in a very conventional way—after all, I did go into the Marines, and I volunteered to go to Vietnam—the idea of being called traitor was very, very painful. But even at the beginning, I felt that people who would use that term didn't understand our country very well, or our Constitution.

In many other countries, you work for a führer, to use the German word: a leader. And the leader is the government. You can't criticize the administration without being regarded as treasonous. That's one of the reasons that a revolution was fought over here, a war of independence.

In my case, the loyalty was to the Constitution and to the country rather than to the administration. Every officer in all the armed services and every member of the Congress and every official in the executive branch all take the same oath. The president's is a little bit different, but everybody else has the same one, and it's not to a leader, and it's not to secrecy. It's to support and defend the Constitution of the United States against all enemies, foreign and domestic. I had been violating that oath, I would say, when I knew that a president was violating the Constitution and waging war under false pretenses. In the end, I felt that the right thing to do, definitely, was to tell the Congress and the public what was being done in their name. That certainly seemed to me like being a better patriot than I had been.

When you last spoke to Reason more than 40 years ago, you said you were a former Cold War Democrat who was "in transition" and "very influenced by the people who are radical pacifists and anarchists." I'm curious about how you would describe your politics since then.

I was influenced really by nonviolent activists in the Gandhian tradition and the Martin Luther King tradition. Giving the Pentagon Papers was a radical action. It involved truth telling and risk to myself. I expected to go to prison for life.

I still want to live up to that tradition. But I never became a total pacifist. I don't agree with those of my friends who are critical of all wars. The truth is, though, that there hasn't been one since the Second World War that I could really recognize on our part as having been justified or worthwhile. So I remain very much anti-imperial and very skeptical of intervention.

I found it interesting that you use World War II as an example of a justified war. In your recent book, there's some mention of your dislike of the tactics the Allies used.

Well, look, to say that I thought the war was just and even necessary against Hitler does not mean that I would endorse our tactics. I thought that the firebombing of Germany toward the later stages, and the entire bombing of Japan, which consisted of trying to kill as many Japanese civilians as possible, was a clear-cut war crime from beginning to end. Indeed, if you're really to take the idea of war crimes seriously, no question, it should have been prosecuted.

I don't think you can understand the nuclear age and how it came to be if you don't know the history of World War II. Most people don't know—they bought the government line that our effort was only to hit military targets in a narrow sense, and that other people were being hit only by accident, in what we now call collateral damage. That was a flat-out lie from '42 on. They were imitating the Nazi tactics in the blitz. That departed entirely from the notion of "just practice" in war, as opposed to "just cause." Unfortunately, that precedent worked itself out in the worst possible way. The legitimation [of using nuclear weapons] really came before Hiroshima and Nagasaki, which in turn simply reflected what our Air Force had been doing for the previous year.

By the way, are you asking these questions from the point of view of a total pacifist?

I'm OK with self-defense, but I think it's hard to find a justified war even if you think some conflicts within that war were justified.

The occasional somewhat violent uprising is successful, but it's very few. That's why I'm much more committed to the idea of nonviolent resistance efforts of various kinds. But in the case of [justified tactics during] World War II, I would point to the British actions in the Battle of Britain. The dogfights in the air, but also anti-aircraft [attacks] against bombers. I not only see that as justified—or as some pacifists will say, "I don't condemn that"—I think they were doing the right thing. They did prevent the invasion of Britain. And I don't think that nonviolent tactics against those bomber planes would have been as effective at all.

I agree. But there are people who slide from that into "and therefore every Allied tactic was justified because they had to win, and they did win, and therefore they had to do all that in order to win."

Yeah. But that's based just on an assumption. It doesn't bear up to real historical analysis of what exactly happened and whether it was necessary or not. Sure, people will say that at the time they thought the bombing of cities was not only effective but necessary. But that turned out to be untrue. There remains no justification, and that was fairly clear as the war was going on. It had to be kept from the public in both Britain and America because the leaders knew that it did not stand up morally.

"In the end, I felt that the right thing to do, definitely, was to tell the Congress and the public what was being done in their name."

The Russians were fighting under Stalin for a terrible regime, and many of them knew it—but they were fighting against Nazi invaders. A pacifist friend of mine recently said, "Look, they lost 20 million people. What could be worse than that?" A fair question, except that if one was to look into the German plans you'd see that what they had in mind was depopulating Russia to the point of killing by starvation 30–40 million people.

So even under the terrible conditions of the Russian front, they were fighting for their lives, and I think justifiably.

Let's talk about your new book. Could you sum up the bizarre circumstances by which you lost the other papers?

I decided in 1969 when I started copying the Pentagon Papers that, since I'm doing this, I should really put out information far more significant than the information on Vietnam, and that was the dangers for human existence that we have been building up and which the Russians have been imitating now for some years.

I copied everything in my top-secret safe, much of which dealt with nuclear matters. Not operational details, but the fact that we were contemplating first use and first strike—disarming attacks on the Soviet Union—and this resulted in a very dangerous situation, especially because the Russians were doing the same.

I was influenced by the example of draft resisters like Randy Kehler, who were on their way to prison for nonviolent resistance to the draft. I concluded that if that was the right thing for these young men to do, I could and should do that also, by telling the truth. I saw Randy Kehler just before he was due to go to prison in San Francisco, and I told him what I was doing at that very moment in the way of copying. He thought it wasn't important to put out the Pentagon Papers, because enough about Vietnam had come out already. What was really new and important was the nuclear material. I said, "Well, I agree with him on the importance, but Vietnam is where the bombs are falling right now, and I want to do what I can to shorten that war by informing people what was being done in their name." My plan really was to go through my trial—maybe a couple of trials, for distribution as well as copying—and then put out the nuclear papers.

That didn't happen because I gave them to my brother who, to shorten the story, hid them in a town dump, and a hurricane actually came through and disturbed the trash field that he'd buried them in, including moving the stove that he'd used to mark the location. It's just impossible to find the box containing the nuclear papers anymore.

That would almost certainly have put me in prison to this day, and nevertheless I regretted very much that I didn't have the chance to do that. It's been kind of a cloud over my life for the last 40 years, but I'm dispelling that cloud now by telling the substance of what was in those documents. A number of them have been declassified in the intervening decades by Freedom of Information Act requests—enough to at least, I think, show that what I'm saying in general is verifiable. I'm just hoping I'll have something of the effect in awakening people to these dangers that I could have had earlier.

What is the biggest misconception the public has about nuclear war?

People are worried about North Korea for good reason. North Korea is a nuclear state against which our president is threatening military action, and that military action would very likely escalate. Even if we didn't begin it, to attack North Korea has a very great risk of getting a nuclear response, which would lead to nuclear use by us for sure, and it just possibly could start with nuclear use by us. Everything is on the table, as [President Donald Trump] says—and as you know, I quote nearly every president as having used those words.

Here's the thing I think that people don't understand: Trump, crazy as he looks compared to others, is simply following tradition in terms of nuclear threats. I don't think any president has ever said to the Joint Chiefs of Staff, "Nuclear first use by the U.S. is out of the question."

In that sense, when Trump shows a willingness to contemplate initiating nuclear war, either in a limited way or in an all-out way, that's not new with him. Hillary Clinton said the same. Bill Clinton. Every president.

[The second thing is that nuclear war would have] a far greater death toll than people think. Our Joint Chiefs [in 1961 were preparing for] a war that would have resulted in over a billion deaths out of 3 billion people in the world. But that was mistaken even at the time. I didn't know and the Joint Chiefs didn't know and the president didn't know [about the disastrous effects of] the smoke from the cities that they proposed to burn simultaneously by nuclear weapons.

With nuclear weapons, the big change is not so much to the fire in one city. You can with incendiaries kill 100,000 people in a night. That's more than were actually killed immediately in either Hiroshima or Nagasaki. But as we developed hundreds and later thousands of nuclear weapons, you could do that essentially to hundreds or thousands of cities at the same time, causing firestorms in each of those cities.

Such a fire over a large enough area simultaneously will cause very strong updrafts. The cold air—the oxygen from the outside—like a bellows can blow the smoke from all of this into the stratosphere. And in the stratosphere, the smoke doesn't rain out, and moreover, we've learned that when it goes that high, it subsequently gets warmed by the sun and goes even higher, to a level that surrounds the globe and prevents sunlight. Not altogether, but as much as 70 percent of the sunlight. More than enough to cause winter conditions of below-freezing temperatures, at night especially, in the summer. What they call "nuclear winter."

That in turn causes a famine, because it destroys harvests worldwide. A war between U.S. and Russia would destroy harvests for about a decade, and a year of that is enough to kill nearly everyone. Even though perhaps 1 percent of humans would survive—and that's a lot of people now, 70 million people—other animals would not. They can't adapt the way humans can, and nearly all other large species would go totally extinct. We'd be left with a world of microbes. So we're talking about something that can be fairly called "doomsday."

Our weapons are mainly designed for fast pre-emption, that is to say, striking first. That's been crazy for over half a century. Each side has enough warheads at sea that can't be destroyed in a pre-emptive attack to cause nuclear winter. And even if you didn't know about nuclear winter, they're enough to destroy hundreds of millions of people. The idea that it's beneficial or optimal to strike first rather than second has been a hoax and a delusion since the mid-'60s at least.

So why has this doomsday scenario not happened?

Partly because the enmity between the leaderships of the two sides in the Cold War was not as aggressive as we claimed. If they had been as Hitler-like as we claimed the Russians were, we wouldn't be here, period.

But it's so easy for humans to find reasons for doing terribly reckless things. Self-serving reasons: private interest, staying in office, making money, being powerful within an alliance. They're all real reasons, but from the point of view of the survival of humanity, they don't remotely justify the risks that are being taken. In other words, we've got a reasoning animal here—humans—who in collective form are capable of doing things that threaten our survival enormously. We built up this doomsday machine based on false premises. The missile gap, and that the Russians were Hitler and were trying to invade us. Even looking at evidence, which sounds good, is not a very strong protection, because as we're seeing, the people who deny climate change look at evidence. They're just able to interpret it in a way that conforms to their chosen beliefs.

In short, we need more than reason to get out of the predicament we're in, and it's not clear whether humans will rise to that. If catastrophe occurs, it will be not entirely as a result of impulse. It could be the implementation of preparations that have been made over decades.

You note as a metaphor that using a gun doesn't necessarily mean firing it. It can mean brandishing it.

Right. The arguments for the arms race are remarkably like those of the [National Rifle Association]. "It's not the weapons, it's the people," and "You have to have them for defense," and so forth. I think that a case can be made for deterrence, for having some weapons. A case that is not by any means entirely foolish. But let's look at the tyrannical, ruthless regime of Kim Jong Un. I haven't seen any evidence that he really wants to expand, but he is determined to stay in power. He believes that his likelihood of staying in power would be greater if he had a weapon to threaten the U.S. with. Is he wrong?

Probably not.

His process of trying to get that weapon may lead to his being attacked, so that process is dangerous. But on the other side of it, as he says every day, "I need those weapons." If he were to stop entirely, the chance that he would go the way of [former Libyan leader Moammar] Gadhafi is definitely higher.

By the way, that doesn't give him a reason for having a doomsday machine. There is no good reason for having the capability to kill a billion people. Prior to Trump, how many weapons would it take to deter a [U.S.] president from a major attack? How many of our cities would have to be threatened?

God, I don't know.

A lot of people would say that a reliable prospect for destroying one U.S. city would be a quite strong deterrent. You might think, "Well, you'd need more than one weapon to have that reliability, 'cause we would destroy some [of their missiles before they hit us]." But do you need a thousand weapons? I would say not. Herb York, who was the first director of Livermore Laboratory, one of the two nuclear design laboratories along with Los Alamos—he asked himself, "How many weapons do you need to deter a rational leader from attacking you?" He said, "One to 10, and less than a hundred—but closer to one than a hundred." That seems quite reasonable, I would say. That's what North Korea has at the moment.

Kim Jong Un "doesn't have an ICBM that can reach an American city with a fission weapon. But he does have boats, and that's all it takes to bring the warheads that he has to Long Beach or to San Francisco Harbor."

The others all have more. There was a point at which there were 70,000 nuclear weapons, most of them thermonuclear. Not 10, not 20, not 100. Seventy thousand. Now, that was all done for reasons. Nobody did that absentmindedly. It was argued, it was budgeted, it was planned, it was produced, it was developed over years.

We have a president at the moment who wants the total denuclearization of North Korea. Well, that would be good. Is it going to happen? No. Why not? Because Kim is not going to give up his nuclear weapons. He believes—correctly, I would have to say—that his chance of surviving to an old age would be much less if he gave them up. So that's a non-achievable goal.

How about a lesser goal? Freezing his nuclear weapons program. No more testing, no H-bombs, and no ICBMs [intercontinental ballistic missiles]. I'm for that. Is it going to be achieved by military attack? You can destroy the regime with a military attack, but you'll lose probably several million allies in the process and quite possibly an American city. [Kim] doesn't have an ICBM that can reach an American city with a fission weapon. But he does have boats, and that's all it takes to bring the warheads that he has to Long Beach or to San Francisco Harbor. I think he's probably prepared to do that, and we seem to have a president who I can't say is thoroughly deterred by that prospect. [Trump] does act in a number of ways as if he's one of those rogue heads of state we hear about who can't be deterred.

It's hard to contemplate the scale of nuclear destruction that our stockpile is capable of, and that may be part of the problem.

I want to see the doomsday machines dismantled, and that means not just the U.S. and Russia, but all systems that can cause nuclear famine. That means reductions by Britain, France, China, Israel, all of 'em. Would I like to see North Korea get rid of all its weapons? Yes. Absolutely. But they're not going to. On the other hand, would I like to see 'em stop where they are now? Yes. That is achievable by negotiation. It means concessions on our part like ending the state of war between the U.S. and North Korea. Having a peace treaty, in short.

Does North Korea want that?

North Korea's been asking for that for many, many years. But to get a freeze, we have to stop threatening the assassination of Kim Jong Un. You say, "Well, Kim Jong Un is a very bad guy." That's true. He's murderous. He's a tyrant. I'm [also] not in favor of military action to change the regimes of Saudi Arabia or Egypt or China, all of whom have tyrannical regimes. I would give up our imperial pretensions.

Do you ever imagine what would have happened if you hadn't decided to leak the papers? If you could have done anything to mitigate the harms caused by Vietnam or our nuclear policy if you had stayed in the corridors of power?

[When I worked for the government] I was attempting to make things more reasonable, both on nuclear matters and on Vietnam. I was totally unsuccessful. Just as many cities would have been hit after my efforts as before, even though the plans I wrote called for withholding cities [from nuclear attacks]. They weren't going to do that. They changed the names of the targets from being cities to being military targets, so-called, within the cities—industries, transportation hubs, command-and-control centers, air defense. The cities would have burned. The same amount of smoke would have gone up. Working as an insider without Congress and the public ever knowing what we really planned to do, it had no effect.

[Former Secretary of State] Colin Powell, to move ahead here, knew that attacking Iraq was a very bad idea, but I'm sure he told his wife, "If I get out, I leave the president alone with hawks like Richard Perle and Dick Cheney, so I've gotta be in there." A voice of reason. Well, plausible enough. But to no good effect at all. He was against torture; he couldn't stop it.

Actually, it was others who did reveal it. Did the leaking eliminate it? No. But it greatly reduced the amount of torture we conducted. So whistleblowing has had some effect.

What do you hope your legacy will be?

I would like others to believe that they have the power—and the obligation, really—as patriots, as human beings, to reveal what they themselves know are unjustified dangers to human existence. And not simply, for reasons of career and promises to superiors, to conceal dangers of that nature. In other words, to be truth tellers.