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HIROSHIMA, Japan (AP) — In this place where a fearful age was born one fiery instant 65 years ago, the Flame of Peace still flickers on, awaiting the day when the world is rid of nuclear weapons.

Many believe that day may be approaching.

"I saw a light in a dark tunnel," says Emiko Okada, 73. "President Obama said, 'Yes, I can.'"

For her and other "hibakusha," survivors of Hiroshima 1945, abolishing nuclear weapons has been a lifelong crusade. But the cause that Hiroshima never abandoned is now also the cause of a growing movement worldwide, embraced by statesmen in Washington and other capitals, endorsed by old Cold Warriors, promoted by Hollywood, financed by billionaires.

Ordinary people, too, in country after country, want "zero nukes," opinion polls show.

But is it achievable? Can doomsday arms be banished from the face of the Earth? Will man stop reaching for ever more powerful weapons? And, more immediately, will an American president, following his ambassador's unprecedented visit, finally walk this year among the cherry trees, the memorials, the unspeakable memories of Hiroshima?

"The hibakusha say, 'We're getting older and older and we'll soon die.' For them abolition is a kind of dream that should be achieved immediately," says Kazumi Mizumoto, 53, a Hiroshima-born scholar of the nuclear age. "I understand their feelings. But feelings aren't enough."

The strongest feelings are of obligation — to the countless thousands whose ashes lie beneath the burial mound beside the Ota, the tidal river that ebbed and flowed with charred bodies on Aug. 6, 1945, after U.S. airmen dropped a bomb that, in a blinding orange flash, unleashed the atom's unearthly power on an unsuspecting city below.

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In movie houses across America this summer, the Hollywood film "Countdown to Zero" is exhorting audiences to "change our way of thinking" and eliminate nuclear arsenals. In a second documentary, "Nuclear Tipping Point," distributed via 50,000 DVDs and screened for President Barack Obama last April, former U.S. Secretary of State George P. Shultz warns of "a very dangerous moment" in history and calls for zero weapons.

The first film was financed by former eBay chief Jeff Skoll, and the second by the Nuclear Threat Initiative, an organization underwritten by two other billionaires, Warren Buffett and Ted Turner.

Such heavyweight backing points up the movement's newfound clout. It will need every ounce of it in contending with the inertia of the nuclear age.

The age unfolded slowly at first. After dropping bombs on Hiroshima, killing at least 140,000 people, and three days later on Nagasaki, killing at least 80,000, the U.S. took Japan's World War II surrender and built only three more bombs in 1945. But by 1949, when the Soviet Union tested its first device, the U.S. had 235, and the arms race between Cold War adversaries was joined.

The "nuclear club" expanded in the following decades, to include Britain, France, China, Israel, India, Pakistan and probably North Korea.

At its peak, in 1986, the global stockpile totaled more than 70,000 weapons, 96 percent in U.S. and Soviet hands — not just aerial bombs and missile warheads, but also nuclear land mines, naval depth charges and artillery shells, equivalent to three tons of TNT for every person on Earth.

Through those years, the world teetered on the edge of a catastrophic nuclear exchange an unknown number of times, from 1962's Cuban Missile Crisis to false alarms and near-launches never publicly reported.

It wasn't until the Cold War ended in 1991, as the Soviet Union disintegrated, that a "builddown" of strategic weapons began, with the first treaty reducing long-range nuclear missiles. But reduction was not elimination: By 2007, arsenals still bristled with 27,000 atomic warheads, enough for more than 150,000 Hiroshimas.

In January that year, a pivotal opinion piece appeared in The Wall Street Journal, signed by Shultz and Henry A. Kissinger, former secretaries of state; William Perry, a former U.S. defense secretary, and ex-U.S. Sen. Sam Nunn, chairman of the Nuclear Threat Initiative.

These four elder statesmen made two powerful arguments for abolition: Cold War-style nuclear deterrence was a long-obsolete notion, and the threat of nuclear terrorism, accident or miscalculation grew with every year that thousands of weapons and tons of weapons material existed.

Their appeal gave new hope to abolitionists. In 2008, momentum built as both U.S. presidential candidates espoused the no-nukes goal, and a new high-profile movement, Global Zero, took shape, led by Jordan's Queen Noor and former U.S. arms negotiator Richard Burt and backed by such leading figures as former Soviet President Mikhail S. Gorbachev.

Then, in April 2009, the new U.S. president and Russia's President Dmitry Medvedev jointly endorsed the "zero" goal, and Obama, in a historic address in Prague, Czech Republic, declared that the U.S. must act "as the only nuclear power to have used a nuclear weapon" — a rare statement of U.S. moral responsibility.

By April this year, the American and Russian leaders were signing a new treaty taking their countries' arsenals down another notch, to 1,550 deployed warheads, with several thousand in reserve. That pact awaits U.S. Senate ratification.

The abolitionists, meanwhile, have rolled out their plans.

Global Zero's study group of former U.S., Russian, Chinese and other military and diplomatic leaders proposes a phased process whereby the U.S. and Russia negotiate down to 1,000 warheads each by 2018. Meanwhile, by mid-decade, other nuclear-armed nations would enter multilateral talks to reduce their weapons in proportion to continuing U.S. and Russian cuts. All would reach zero by 2030.

Mayors for Peace, representing 4,037 cities worldwide and led by Hiroshima's Mayor Tadatoshi Akiba, is even more ambitious, calling for abolition by 2020.

The most detailed, step-by-step blueprint comes from the International Commission on Nuclear Non-proliferation and Disarmament, sponsored by the Japanese and Australian governments. That 300-page report, issued last November, foresees "minimization" — a world of no more than 2,000 warheads — by 2025, and elimination of the weapons over an undefined period to follow.

"We did not feel it was practical to set a date" for elimination, commission co-chair Yoriko Kawaguchi, former Japanese foreign minister, said in a Tokyo interview.

She likened it to climbing a mountain and not seeing the top until halfway up, when one can better judge how to get there.

"It's not easy but we will have to do it. We will have to change the world," she said. "If you go to Hiroshima, you realize the atrocity of nuclear weapons."

But "realists" have been quick to dismiss what a former U.S. defense secretary, Harold Brown, calls the "practical impossibility" of zero nukes.

For starters, they say, Russia, China, India, Pakistan and France, each for its own reasons, would resist giving up their arsenals — Russia, for example, out of concern about a large U.S. conventional military advantage. They argue, too, that such countries as Germany and Japan, reliant on U.S. nuclear protection, would be tempted to build their own if they saw the U.S. moving to dismantle its weapons.

Abolitionists counter that progress clearly depends on political will and leadership to overcome such nationalistic concerns.

"One thing we have learned is that working just on the basis of self-interest, this does not work," Gorbachev said in a 2009 AP interview. If the U.S. and Russia together take the lead, he said, "then the next steps will come from other countries."

What about cheaters? the skeptics ask. What if the world goes to zero, but Iran decides to build a bomb?

"It's an irrelevant kind of argument," Shultz told the AP last year. If everyone else is dismantling their weapons and Iran looms as the only country with them, "nobody is going to stand for that," he said.

As for detecting secret bomb programs and verifying warhead dismantlement, proponents say the science of verification — through atmospheric sampling, satellite imaging, seismic monitoring and other tools — has advanced to a state of high confidence. And the U.N.'s nuclear watchdog, the International Atomic Energy Agency, would have to be given greater powers of onsite inspection, they say.

Who would enforce a nuke-free world? The ultimate authority, the U.N. Security Council, is often paralyzed when one of its five permanent members, the major nuclear powers, wields its veto power.

Nobuyasu Abe, former U.N. disarmament chief, suggests that under a nuclear ban the five agree not to exercise the veto in the case of an illicit nuclear "breakout."

"If some other country is getting nuclear weapons, they're then agreed to take strong action against it," Abe said in Tokyo.

"Strong action," besides economic or political isolation, might take another, forceful route — resort to a residual nuclear option, the ability to quickly reconstitute atomic weapons to counter a looming nuclear threat. In that sense, whether under control of national or international authorities, the weapons might be gone, but not forgotten.

In the end, champions and critics of "zero nukes" both say, the greatest obstacle lies in the regional clashes that keep the world on edge and nations building nuclear arsenals: India and Pakistan over Kashmir; Israel in its standoff with the Arabs; hostility between the U.S. and North Korea and Iran; the China-Taiwan impasse.

Easing such crises must come first, many say.

"Disarmament is important, but a safer world is more important," said France's Eric Danon, a veteran of disarmament diplomacy.

Abolitionists, on the other hand, hope steady progress and rising demand to eliminate nuclear weapons will in itself help move the world to resolve these disputes.

"I don't think we are sure the world will be stable enough," Kawaguchi acknowledged. "That's why you have to go step by step."

They're also unsure whether the world is aware enough.

"There are probably generations who haven't even seen the images of Hiroshima and Nagasaki," Queen Noor told the AP. "And so they don't have any sense of the reality of what this is."

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Even 65 years later, that reality can seem unreal.

When the A-bomb exploded 600 meters (2,000 feet) above Shima Hospital at 8:15 a.m. on Aug. 6, 1945, its rays doused central Hiroshima with heat reaching more than 3,000 degrees Celsius (5,400 degrees Fahrenheit), twice what's needed to melt iron.

Wind from the blast reached 440 meters per second (almost 1,000 mph), the force of five Category-5 hurricanes.

Death and devastation were instantaneous. Trees, wooden houses, people were suddenly ash, leaving a scorched, empty plain for 2 kilometers (1.2 miles) in all directions.

"Just gray ash desert," recalled Keijiro Matsushima, 81, who survived the collapse of his school outside the worst-hit zone.

All that day, he remembered, a "procession of ghosts" slowly emerged from Hiroshima's flaming core, "burned people like smoked and broiled pigs, faces all damaged and swollen up, the skin nearly peeling off," people doomed to die within hours, and many others to die from radiation poisoning in the weeks to come.

"I want more and more people in the world to know the horrible reality of nuclear weapons," said Matsushima, a retired high school English teacher who leads an abolitionist group of educators.

Robert "Bo" Jacobs tries to give American visitors a sense of that reality as he leads them through the Peace Memorial Park, past acres of poignant monuments, past the Flame of Peace, to be extinguished only when the weapons are.

In the centerpiece museum, "most people are stunned" at the scale of 1945's devastation, said Jacobs, an American researcher-author at the Hiroshima Peace Institute. He then explains to them that Hiroshima's A-bomb pales beside the power of today's thermonuclear weapons.

"I don't think anybody really can grasp that scale," he said.

One who might begin to grasp it, with thousands of potential Hiroshimas under his command, is the president of the United States.

Obama told a Japanese interviewer last November he "would be honored" to visit Hiroshima and Nagasaki. He'll have his chance: The annual Asia-Pacific summit is scheduled for Nov. 13-14 this year in Yokohama, Japan, just when Nobel Peace Prize laureates are gathering in Hiroshima, an hour's flight away. Obama qualifies for both meetings.

Meanwhile, Ambassador John Roos attended Friday's anniversary events here, first-ever official U.S. involvement, a signal that Washington is ready for a role memorializing Hiroshima's victims. "We must continue to work together to realize a world without nuclear weapons," Roos said in a statement issued Friday.

To the hibakusha, Obama "is the leader of the 'Obamajority' abolition movement," said Steven L. Leeper, a longtime American resident of Japan who heads this city's peace park and museum foundation.

November "is an opportunity for him to do something amazing," Leeper said.

But the hibakusha know an Obama visit might produce a U.S. political backlash. "It won't be easy for him to decide to come to Hiroshima," Okada said.

They know, too, that attaining their ultimate goal, abolishing nuclear weapons, also won't be easy.

"Each country is selfish, after all. They want to defend themselves," Matsushima said. Being "a kind of realist," the old teacher said, he had "thought and thought" about abolition, "and I concluded it would be very, very difficult."

Tranquil and green, crisscrossed by visiting schoolchildren, Hiroshima's peace park spreads over a point of river delta where, on that day 65 years ago, crazed and desperate parents searched in vain for thousands of children who had been brought to the city center to help clear firebreaks.

It's where for days afterward Hiroshima's burned, numbed, sick survivors piled unrecognizable human remains atop cremation pyres. It's where Okada's 12-year-old sister vanished in that morning's vaporizing heat, as hot as the surface of the sun.

A lifetime later, this quiet, subdued grandmother looked back.

"We have to protect our Earth, so our children and grandchildren will never suffer like that," she said.

And she looked ahead.

"Maybe nuclear weapons won't be abolished while I'm alive," she said. "But I will never give up."