A few days before Thanksgiving in 2021, Daniel Ellsberg looked directly into a camera lens and talked about nuclear preparations for annihilating almost everyone on Earth. “That is insane,” he said. “And you have to call it a kind of ordinary insanity, because it’s so widely shared.”

The new film An Ordinary Insanity condenses Ellsberg’s essential message into a half hour. It follows the acclaimed 2009 documentary The Most Dangerous Man in America: Daniel Ellsberg and the Pentagon Papers. Judith Ehrlich—who codirected that Oscar-nominated movie and is the director of An Ordinary Insanity—says that “as his understanding of nuclear war evolved, Dan confronted it for us and dug deep into its roots.”

When Ellsberg gave the 7,000 pages of the top-secret Pentagon Papers to The New York Times in 1971, he was risking the rest of his life in prison for exposing the official deceptions behind the Vietnam War. That brave act, causing him to be vilified and beloved, began his five decades of tireless antiwar efforts. Through it all, his main preoccupation continued to be reducing the risk of nuclear war.

Early in his professional life, Ellsberg had become a “national security” insider, with expertise in the command and control of nuclear weapons along with strategic planning. Access to official calculations made him aware of scenarios for initiating Armageddon. Some classified plans for starting a nuclear war, with a first strike on the Soviet Union and China, were beyond shocking.

“The Joint Chiefs of Staff estimated in 1961 that the effects of our carrying out those plans, the annual operational plan for which the weapons existed and were on alert, they estimated it would kill 600 million people. A hundred Holocausts,” Ellsberg says in An Ordinary Insanity. “When I saw that estimate in the White House, I thought that was the most evil planning that had ever existed in the history of humanity.”

As scientific research advanced and climate modeling discovered nuclear winter, estimates like 600 million became outdated. “For only the last 40 years of the nuclear era, not considered at all before 1983, we’ve known soot and smoke was a crucial lethal effect of nuclear weapons,” Ellsberg recounts in the film. “The firestorms created by nuclear weapons would have lofted the smoke from these burning cities into the stratosphere, quickly enveloped the globe and blot out most of the sunlight, not all of it but about 70 percent of the sunlight, which would create winter, killing all harvest for at least several years and up to a decade or more, starving nearly everyone. Not quite everyone. It wouldn’t be an extinction event. Ninety-eight percent gone within a year, starving to death.”

While working at the military-enmeshed Rand Corporation think tank before leaking the Pentagon Papers to the press, Ellsberg had been studying what he describes as “the highest-stakes hypothetical gamble in human history, whether or not to launch nuclear missiles on the basis of ambiguous warning.” That quest for understanding led him to the conclusion that ICBMs—the land-based part of the air, land, and sea triad—are the most dangerous component of the unspeakably dangerous nuclear arsenal.

The importance of eliminating ICBMs figures prominently in Ellsberg’s landmark book The Doomsday Machine: Confessions of a Nuclear War Planner, published in 2017. The Nation later printed an article that he and I cowrote to emphasize the point: “The single best option for reducing the risk of nuclear war is hidden in plain sight. News outlets don’t mention it. Pundits ignore it. Even progressive and peace-oriented members of Congress tiptoe around it. And yet, for many years, experts have been calling for this act of sanity that could save humanity: Shutting down all of the nation’s intercontinental ballistic missiles.”

Those missiles, on hair-trigger alert, are the only weapon that forces a president into “the urgent decision of whether to launch nuclear war,” Ellsberg explains in An Ordinary Insanity: