For some reason it gives me chills to think that the youngest survivor of the atomic bomb dropped on Hiroshima is now nearly 40.

Koko Kondo, a friend of mine, was 8 months old on Aug. 6, 1945, when, at precisely 8:15 a.m., the solitary Enola Gay slipped "Little Boy" from its bomb bay and obliterated this sunny delta city in what residents call the peeka-dohn -- "flash-bang" -- effect. Thus began my friend's childhood as a target for the first atomic bomb dropped on human beings.

Today, Koko is 38. She, naturally, does not remember a thing about that now distant morning. Some of her earliest memories begin with a sort of human chain reaction of bomb-related illnesses--leukemia, thyroid cancer, diabetes--that started taking friends and relatives out of her life in disproportionate numbers. There were her own fears of "getting sick."

Koko, a sprightly, outgoing woman, doesn't dwell on her personal tragedies. A graduate of American University in Washington, she is married and has a young adopted daughter. She devotes her spare time to what she calls, simply, "peace work." Dreams of having a child of her own were shattered a couple of years ago when she suffered a miscarriage. Doctors said there was no evidence to link it to her exposure to radiation as a child, but she wonders.

What bothers her today is what she interprets as a kind of collective amnesia taking hold in Japan.

"To the young mothers of today," she said recently, "Aug. 6, 1945, is ancient history. They should take a more active role in telling their kids about the war and Hiroshima, but they don't really care."

In Hiroshima today, there are 90,000 survivors of the bombing out of an estimated 370,000 nationwide. On a recent visit to the city, my third in 12 years, I found the hibakusha, as the survivors are called in Japanese, still talk with a quiet dignity about their experiences -- the sudden and utter devastation, the misery and years of living in the shadow of disease.

With a kind of understated missionary zeal, their representatives try to convey their message, "No More Hiroshimas," the slogan that originated here nearly four decades ago, to the rest of world. But behind the indomitable spirit, the civic pride, there is a growing pessimism that their antiwar message will be heeded, not only by the Americans, the Russians and the Europeans, but by the Japanese themselves.

To be sure, the vast majority of Japanese remain adamantly opposed to the idea of building or possessing any nuclear weapons of their own, although there is widespread acceptance of protection under the American "nuclear umbrella."

A massive buildup of Japan's conventional military armor is forbidden under the terms of the country's American-engineered constitution of 1947. And talk among conservative intellectuals and politicians about removing these constraints by rewriting the constitution has so far met with a chilly reception.

At the same time, however, there are signs that Japanese attitudes toward war and peace are rapidly changing. At the United States' behest, Japan has embarked on a gradual military buildup that, if all goes according to plan, will give the country, among other things, the world's sixth largest modern navy by the end of the decade.

These changes, modest as they may appear by American standards, indicate in the view of responsible Japanese pacifists a growing public acceptance of an expanded defense role for Japan that, ultimately, could entangle the country in another war, nuclear or otherwise.

More important, they say, a new fascination among a younger generation of affluent Japanese with magazine articles, movies and bestsellers extolling Japan's aggressive military past has trivialized bitter wartime experiences and indicates an erosion of the country's ostensibly peaceful postwar values.

Is it possible, as these observers contend, the Japanese are in danger of forgetting what the hibakusha call the lessons of Hiroshima?

Takeshi Araki, Hiroshima's mayor, likes to tell how, when the first teams of scientists converged on the city in the frantic days after the bombing, some of them predicted that no trees or grass would grow here for 75 years. Only a few weeks later, he said recently, "we saw the wild grass growing from the ruins of our city, and we started to have hope again."

Largely rebuilt in the 1950s, Hiroshima is laid out with broad avenues and generous green spaces that are rare in the jerry-built congestion of other Japanese cities. Today, it has a population of 900,000, more than twice that of wartime days. Toyo Kogyo, the maker of Mazda cars and trucks, has its headquarters here, and the city's booming industries have made it the hub of southwestern Japan's regional economy.

At the center of Hiroshima's broad riverine basin, amid the trappings of feverish growth, lies the Peace Memorial Park, almost directly below the point where the bomb exploded at an altitude of about 1,500 feet. Thousands of Japanese converged here in August to march and chant peace slogans to mark the 37th anniversary of the bombing.

Echoing the outwardly hopeful sentiments of other hibakusha like himself, Hiroshima's mayor, Takeshi Araki, told the crowd: "Hiroshima is an everlasting warning for the future of mankind. If Hiroshima is ever forgotten, it is evident that the evil will be repeated and human history be brought to an end."

In an earlier conversation, however, Araki, an urbane and practiced politician, suggested that he was disappointed with what he views as a widespread apathy toward the antinuclear campaign in Japan that has given the yearly observances here a largely ceremonial cast.

Compared to the fears that have sparked an upsurge in protest recently in the United States and Europe, he said, "The Japanese awareness of the dangers of nuclear war is much less."

Unprecedented levels of prosperity, an historical sense of physical isolation from the outside world and the absence of a clear threat to the country's security have contributed, in the past three decades, to a lukewarm attitude in Japan toward the antinuclear movement. "In a way, you could almost say that Japan has been almost too peaceful."

A large share of the blame, many of the hibakusha here contend, lies with Japan's own postwar peace movement. Dominated by the country's Socialist and Communist parties and their affiliated labor unions, the movement has remained since it was organized in the mid-1950s in a state of isolated -- disembodied, one might almost say -- idealism.

Insisting on the complete and immediate abolition of nuclear weapons, the two rival groups generally have spent more time fighting each other than campaigning against the arms race or nuclear testing.

Tolerant of the Soviet Union and highly critical of the United States, the movement has effectively hamstrung efforts at developing grass-roots support by alienating the majority of Japanese who are mostly pro-American and traditionally distrustful of the Soviet Union.

"The Europeans have the threat of a nuclear war right in their backyard," says Takao Tokuoka, a senior writer for the mass-circulation daily Mainichi, "but they generally realize the need for a gradual reduction of nuclear weapons . The Japanese, on the other hand, have tended to take a very fundamentalist approach, so idealistic that . . . it's all rather boy scoutish."

Survivors like Ichiro Moritaki, a leading figure among Hiroshima's hibakusha, have often been disheartened by the movement's fractured politics and at times have been criticized by movement promoters for trying to avoid entanglement in the seemingly endless doctrinal disputes. Moritaki, like many others in Hiroshima, prides himself on his independent views and his lack of affiliations with the large national umbrella groups.

By the morning of Aug. 6, 1945, rumors had already begun to circulate about the possibility of an enemy invasion of the Japanese islands, Moritaki, now 81 and retired from his post as a professor of ethics at Hiroshima University, recalled recently. He was at his desk, about 2 1/2 miles from the "hypocenter," completing an entry in his diary for the previous day in elegant brushstrokes. "A beautiful sunrise. The military supervisor ordered my students to make 500 bamboo spears," he said.

Suddenly, the sky filled with a blue-white flash, the color of a Fourth of July sparkler. Temporarily blinded by the explosion, Moritaki was led by his students on a gruesome trek in search of medical help.

"One of my students was describing the scene to me in vivid detail," he remembered, "but it all sounded so incredible that I used my fingers to pry open my swollen eyes to try to see for myself." Amid mounds of rubble and a mounting firestorm, he saw "hundreds of charred human bodies" stacked like cordword along the streets and many more choking the city's rivers, "like logs drifting out to sea."

Lying on a hospital cot some time later, he said, "I decided that unless mankind turned from a civilization based on power . . . it would be destroyed." Self-consciously, he added, "That may sound very abstract. But today, remember, there are 50,000 nuclear warheads in the world, the equivalent of 1 million bombs of the size that was dropped on Hiroshima.

"You must realize," he explained, "that the experience of the atomic bomb is my own personal experience, and now I see the world pursuing a very dangerous course." At times, he said, he despairs of the lack of concern among today's younger generation of Japanese but still hopes that a growing sense of crisis might trigger what he calls a "chain reaction of spiritual atoms" in protest against nuclear weapons.

The inscription on the cenotaph that marks ground zero in Peace Memorial Park says: "Rest in Peace -- We Will Never Repeat the Evil." Most Japanese, today, Moritaki said, interpret the "We" to mean mankind, but "actually, it means 'We Japanese' in its very strictest sense. The fact is that, in the last war, we were aggressors."

At present, the Japanese appear deeply ambivalent in their attitudes toward questions of national security. American pressure for Japan to spend more on defense has helped intensify the soul-searching and touched off a sharp debate on the wisdom of a prolonged military buildup.

That debate swung into high gear following the Soviet invasion of Afghanistan in 1979, which prompted conservative opinion leaders to point to the dangers to Japan of the expansion of Russian naval power in the Pacific and Indian Oceans.

Previously, Tokuoka said, "it was strictly taboo to talk about defense issues without being excommunicated from intellectual debate. We've shed those foolish ideas and now many people are considering why we should stand naked toward an aggressor. The only thing that has remained unchanged is the attitude toward the possession of nuclear arms."

Pacifist critics assert that the country's ruling Liberal Democratic Party, which is conservative despite its name, is attempting to prepare public opinon for the eventual rewriting of the antiwar clauses of the Japanese constitution, which, as now widely interpreted, prohibits Japan from possessing anything but a "minimum and necessary" military force of a purely defensive nature.

They also charge that the government has knowingly nibbled away at the country's longstanding "nonnuclear principles," which ban the possession, production or entry into Japan of nuclear weapons.

"It's a bit too early to tell whether the people--those who oppose nuclear weapons and the rightward drift in society--are really becoming isolated," Kenzaburo Oe, a Japanese novelist widely known for his writings on the Hiroshima bombing, said in a recent interview.

Elsewhere Oe has noted, however, "At the end of the war we made a resolution . . . to obliterate all the factors on our part that contributed to the dropping of the atom bombs on Hiroshima and Nagasaki. Now , however, those factors are reemerging as if Japan's experience of defeat in the Pacific War were to be nullified."

On a sweltering morning, I visited Hiroshima's Peace Memorial Museum, which is located in the park near ground zero. Here, despite the heat and the early hour there are already large numbers of tourists -- a handful of foreigners, but mostly Japanese from other cities -- filing past its grisly exhibits.

The photographs of hideously burned victims, fragments of clothing and a collection of scorched household goods don't appear to have changed substantially since my first visit here in 1970. Museum director Akihiro Takahashi tells me the exhibit has changed very little since the building was opened in 1955.

The reason, as I understand it, is to avoid altering the sense of the original horror of the blast and, by extension, its impact on visitors. A junior high school student here when the bomb was dropped, Takahashi was seriously injured. "Those who were victims of the war were forced to reflect on what Japan did. We know we must not walk that path again."

Today, Takahashi is concerned about what he sees as the absence of a similar awareness among school-aged Japanese. In recent years, Japanese school authorities have deleted or condensed textbook references not only to bombs dropped on Hiroshima and Nagasaki, but also passages concerning the Japanese attack on Pearl Harbor.

As a result, he suggests, a new generation of Japanese is growing up largely ignorant of an accurate, balanced view of Japan's aggressive military role in the war and its subsequent defeat.

Younger Japanese, he says, are being taught to accept without question the need for an expanded military role for Japan.

"Today's young people think war is very chic," he says. "TV and the movies have had a great influence on them. They think that the story of Hiroshima has nothing to do with them."