Late in a life lived unnervingly near the nuclear abyss, William J. Perry is on a mission to warn of a "real and growing danger" of nuclear doom.

The 88-year-old former defense secretary is troubled by the risks of catastrophe from the very weapons he helped develop. Atop his list: a nuclear terror attack in a major U.S. city or a shooting war with Russia that, through miscalculation, turns nuclear. A terrorist attack using a nuclear bomb or improvised nuclear device could happen "any time now - next year or the year after," he said in an interview with reporters earlier this month.

Perry chooses his words with the precision of a mathematician, which he was before entering the defense world in the mid-1950s. He played a central role in developing and modernizing nuclear forces throughout the Cold War - first as a technology whiz-kid and later a three-time senior Pentagon executive. During the 1962 Cuban missile crisis Perry was secretly summoned to Washington to analyze intelligence on Soviet weapons in Cuba.

"Every day that I went to the analysis center I thought would be my last day on earth," he writes in a newly published memoir, "My Journey at the Nuclear Brink." He says he believed then and still believes that the world avoided a nuclear holocaust as much by good luck as by good management.

In the interview, he recounted a harrowing incident in November 1979 when, as a senior Pentagon official, he was awakened by a 3 a.m. phone call from the underground command center responsible for warning of a missile attack. The watch officer told Perry his computers were showing 200 nuclear-armed missiles on their way from the Soviet Union to the United States.

"It was, of course, a false alarm," Perry said, but it was one of many experiences throughout the Cold War and beyond that he says have given him a "unique and chilling vantage point from which to conclude that nuclear weapons no longer provide for our security — they now endanger it."

His views are remarkable, not least because they strike at the heart of the conventional wisdom about nuclear weapons that has been embraced by both political parties for decades. For example, Perry thinks the U.S. nuclear force no longer needs land-based intercontinental ballistic missiles, or ICBMs, and can rely on the other two "legs" of the force — bomber aircraft and submarine-based missiles. ICBMs should be scrapped, he says, adding, "I don't think it's going to happen, but I think it should happen. They're not needed" to deter nuclear aggression.

He also opposes the Obama administration's plan to build a new nuclear-capable cruise missile.

Perry looks at Russia's nuclear modernization and U.S. plans to spend hundreds of billions to update its nuclear arsenal and sees irrational nuclear competition.

"I see an imperative to stop this damn nuclear race before it gets under way again, not just for the cost but for the danger it puts all of us in," he said.

When the Cold War ended with the dissolution of the Soviet Union, Perry thought the world had dodged a nuclear bullet. In his first book, co-authored in 1999 with the man now running the Pentagon, Ash Carter, Perry argued that the demise of the Soviet system meant nuclear disaster was no longer an "A List" threat.

By 2014, his optimism had faded, in no small part because of the collapse of cooperative relations between Washington and Moscow, which has ended any realistic prospect of new arms control agreements and, in Perry's view, has put the two countries on a dangerous path toward confrontation.

"We are facing nuclear dangers today that are in fact more likely to erupt into a nuclear conflict than during the Cold War," Perry said in a recent speech.

A soft-spoken man not given to hyperbole, Perry is on a public crusade to persuade people that nothing less than the future of civilization is at stake. What worries him most is that few seem to notice.

"Our chief peril is that the poised nuclear doom, much of it hidden beneath the seas and in remote badlands, is too far out of the public consciousness," he wrote in his memoir.

In his book's preface Perry outlines a nuclear terror scenario, which he calls "my nuclear nightmare, born of long and deep experience."

In his scenario, a small group gets its hands on enough uranium to fashion a crude nuclear bomb, flies it undetected to Washington's Dulles International Airport and slips the bomb into a warehouse in the District of Columbia. From there it is loaded onto a delivery truck and a suicide bomber drives it onto Pennsylvania Avenue midway between the Capitol and the White House. When detonated, it kills 80,000 people instantly, including the president. The news media report a message claiming that five more bombs are hidden in five different U.S. cities, and one will be set off each week.

"The danger of a nuclear bomb being detonated in one of our cities is all too real," Perry writes. "And yet, while this catastrophe would result in a hundred times the casualties of 9/11, it is only dimly perceived by the public and not well understood."