EDITOR'S NOTE _ ``Suits me fine,'' Ronald Reagan said in 1986 when Mikhail Gorbachev suggested they abolish nuclear arms. But the weapons prevailed. Now, in this 50th year of the atom bomb, a changed world is headed down unexpected new paths. Here is a report on how we arrived at this crossroads and where we may go from here.

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By CHARLES J. HANLEY

AP Special Correspondent

HIROSHIMA, Japan (AP) _ ``Look!'' someone shouted. ``B-29!''

Yoshitaka leaped from his desk to the window. A flash of light stunned him, and then his world exploded around him.

When he awoke, buried in the ruins of his school, he could hear classmates singing, trapped and dying boys finding a last breath of courage in a school song.

He sang, too, until the voices faded one by one and he sang alone.

He struggled for hours to pull himself from the rubble. Finally, somehow, he crawled out into a city ablaze, a bloody, broken 13-year-old at the dawn of a dangerous new age.

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A fire still burns in Hiroshima a half-century later.

``That's the Flame of Peace,'' Yoshitaka Kawamoto says of the flame-tipped memorial. ``When we abolish nuclear weapons, we will put out the fire.''

The gray-haired man smiles at the boy inside. ``I may sound idealistic, but I want to be idealistic until the day I die.''

Fifty years into the nuclear age, after generations of missiles and missilemen, after decades of summits and dealmaking, after uncountable radiation victims and unknowable brushes with catastrophe, the nuclear arms race has largely ended.

Just a decade ago, the idea of freezing nuclear arsenals was dismissed as radical fantasy. Today, the United States and Russia are dismantling as many as 4,000 warheads a year. By 2003, under the START I and II treaties, they will reduce deployment of strategic warheads to one-third what it was at the height of the Cold War.

But if the race has ended, the dangers have not.

Just one of 60 missile submarines roaming the oceans still packs the firepower of 1,000 Hiroshimas. Even the three ``minor'' nuclear states _ Britain, France and China _ can still obliterate an enemy instantly. And more and more nations are finding nuclear weapons within their reach.

Viktor N. Mikhailov, who once designed warheads, applauds their destruction.

``Today I think we are on the right path,'' the Russian atomic energy minister said in a Moscow interview. But moving forward will be difficult. ``We are at a very important point in history.''

The road ahead leads not just through missile silos, but through the heart of world economies, including in Japan, where even the lights of Hiroshima's Peace Memorial Museum, the institution that Yoshitaka Kawamoto grew up to head, run on the power first unleashed here one summer's morning a lifetime ago.

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Early in this 50th-anniversary year, some of Mikhailov's scientists made a remarkable journey to the Los Alamos weapons laboratories in New Mexico, to consult with their U.S. counterparts on what to do with plutonium, the deadly leftover from dismantled bombs.

The working sessions among old adversaries closed a historic circle in a sense, for it was in New Mexico's desert that their nuclear arms race began, on July 16, 1945, when specialists of the ``Manhattan Project'' detonated the first atomic bomb.

``What an explosion!'' Maj. Gen. Leslie R. Groves said in messaging Washington about the terrifying energy released when heavy atoms were split in the ``fission'' device.

Three weeks later, at 8:16 a.m. on Aug. 6, 1945, an American B-29 bomber dubbed Enola Gay dropped an A-bomb over Hiroshima equal to 15,000 tons of TNT. Three days after that, a second bomb was dropped on the Japanese city of Nagasaki.

An estimated 210,000 men, women and children were killed outright or died later from the two bombings. Albert Einstein, the physicist whose theories pointed the way to nuclear energy, grieved after hearing of its use. ``If I were to be born again, I would like to be a plumber or peddler,'' he said.

The bombs helped bring the war with Japan to a quick end. But they served a further purpose, too _ impressing the Soviet Union with American might. When the Soviets finally exploded their own nuclear test in 1949, the grim game of technological leapfrog was joined.

In 1954, on the remote Pacific atoll of Bikini, the Americans tested a hydrogen bomb _ in which a fission bomb causes the ``fusion'' of light atoms for an even greater explosion. The fallout from that cataclysmic 15-megaton blast _ equivalent to 15 million tons of TNT _ sickened people on atolls more than 300 miles away.

A doomsday culture grew in America. Schoolchildren were taught to ``duck and cover'' under their desks, to expect a holocaust at any moment. Homeowners were encouraged to build backyard fallout shelters.

The Russians struggled to keep up. They deployed the first intercontinental ballistic missiles in 1958, but were quickly outclassed and far outnumbered by U.S. missiles.

American scientists and engineers went on to develop the submarine-launched missile (1960), the multiple-warhead missile (1968) and the cruise missile (early 1970s) anywhere from two to five years before the Soviets.

Not until the 1980s did Moscow achieve the nuclear parity it long sought, at great sacrifice to an overburdened economy.

Between them, the two superpowers fielded more than 60,000 nuclear warheads, the equivalent of three tons of TNT _ twice the power of the bomb that wrecked the Oklahoma City federal building _ for every person on Earth. The perverse stability of ``mutual assured destruction,'' a balance of terror, took hold.

But the costs were huge, not only in fortunes spent, but in stretches of land _ from Hanford, Wash., to Chelyabinsk in Russia's Urals _ contaminated with the wastes of weapons production, and in unknown numbers of people doomed by fallout from atmospheric testing at Bikini, in Nevada and at Soviet sites.

Global opposition to those tests led to the first success for nuclear arms control _ the Partial Test Ban Treaty of 1963, prohibiting explosions in the atmosphere. The people of Hiroshima lit their ``peace flame.'' But disarmament remained low on the Cold War agenda.

Although the SALT agreements of the 1970s put limits _ high ceilings _ on the costly competition, it took an arms buildup in the 1980s to finally produce an arms ``builddown.''

To rid Western Europe of new middle-range U.S. missiles, the Soviets agreed to eliminate their own intermediate missiles. And that 1987 agreement spurred the broader strategic arms reduction talks _ START.

In 1991, as the Soviet economy reeled, President Bush and Soviet President Gorbachev signed the first START treaty, slashing strategic warheads by one-third. After the Soviet Communist Party collapsed that August, and the Cold War with it, the two presidents went further, withdrawing thousands of short-range warheads from tactical units on land and sea.

In January 1993, Bush and Russian President Boris Yeltsin took the next step, signing the START II treaty to reduce strategic warheads to below 3,500 per side.

``Obviously there's a trend _ to put it mildly,'' a veteran U.S. arms negotiator, Ralph Earle, said in an interview. ``It's clearly to the benefit of the United States and of Russia to reduce their nuclear arsenals.''

Just last month, Earle helped notch another breakthrough, permanent renewal of the 25-year-old Non-Proliferation Treaty, which commits 178 nations to try to keep nuclear weapons out of the hands of all but five nations that already possess them _ the United States, Russia, Britain, France and China.

At that conference, the weapon states agreed to a goal of outlawing underground nuclear tests by 1996 and of halting production of fissionable material for weapons.

Such restraints, nonweapon states believe, will slowly move the world toward abolition of nuclear arms, as prescribed by the Non-Proliferation Treaty itself.

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