Those old enough to remember 1972 have a significant 50th anniversary to look back on, though maybe not to celebrate.

A collective madness was in the air. Youth revolted against it scarcely knew what, for it scarcely knew what. Revolt itself was good, revolt for its own sake, the more violent the better. Violence proved commitment; commitment justified violence; violence would purge society of corruption, cleanse civilization of dross. “Violence,” said Frantz Fanon (1925-61), a radical thinker much in vogue at the time, “is man re-creating himself.” Or as Chinese Communist Party Chairman Mao Zedong (1893-1976) put it, “Political power grows out of the barrel of a gun.” That justified the gun.

Lawyer Tsuneo Furuhata is a former Nagano Prefecture public prosecutor. On Saturday, Feb. 19, 1972, he was getting into his car to go skiing when — as he recalled for the Asahi Shimbun in an interview published this past February — his wife called him to the phone. Four “suspicious persons” had been arrested in the Nagano resort town of Karuizawa. “They may,” his office told him, “be involved with the Rengo Sekigun (United Red Army).”

Founded in 1969, the group represented Maoist politics at its most Maoist. Violence was the shining means to a golden end — unspecified but presumably civilization in full flower. When justice and equality and universal happiness reigned, violence would be unnecessary; until then, those who shrank from it were bourgeois counter-revolutionary defenders of the unjust and unhappy status quo, their passivity itself constituting a violence worse than the violence necessary to root them out.

In March 1970, Red Army members hijacked a domestic Japan Airlines flight to North Korea. A year later, a gun shop raid in Tochigi Prefecture netted the revolutionaries a small arsenal. All through 1971 the group staged riots and protests — notably against the construction of Narita Airport and the terms of Okinawa’s reversion from American to Japanese rule. Riot police seeking to contain them were met with pipe bombs, Molotov cocktails, guns and knives, often to lethal effect. The climax was the Tokyo “Christmas tree bombing” outside a police box near a department store that injured 12.

As police closed in, remnants of the group still at large scattered into the mountains of Gumma and Nagano prefectures. Four of those caught awaited Furuhata in custody at Karuizawa Station. Five others, still on the run, later that day burst exhausted into a nearby mountain lodge called Asama-Sanso. One can imagine the shock of the lodge’s lone occupant, Yasuko Muta, 31-year-old wife of the caretaker. Her husband was out walking the dog. The guests had gone ice skating. The fugitives promised not to harm her if she cooperated. She promised.

The three-story lodge was sturdily built. It made a good makeshift fortress. Police closed in — little knowing, perhaps, that the siege would drag on 10 days. Nor was that all they didn’t know. An internal purge had taken place in the mountains — 14 Red Army members tried, convicted and done to death by their fellows for insufficient revolutionary zeal.

Furuhata too, at first, knew nothing of that. He took particular interest in one of the four prisoners. “What’s your occupation?” he asked. “Revolutionary,” the young man replied, boldly but quietly. He was refined, polite. He’d been a medical student.

“He began to talk to me,” Furuhata told the Asahi. “He asked me if I’d read Dostoevsky’s ‘Brothers Karamazov.’ I said I’d started it once but never finished it. He said, ‘You really should read it.’ It’s the only time a suspect has ever recommended a book to me.”

The two became friends, after a fashion. Furuhata could sympathize, to a degree. He himself had been a student activist, demonstrating in protest against the Subversive Activities Prevention Act of 1952 — the first legislation to be enacted after the allied postwar occupation of Japan ended. What was “subversive”? What the government didn’t like? The authoritarian spirit, protesters feared, was alive and well, even in defeat. Democracy, newly imported and still strange, had to be guarded, nurtured, perhaps fought for — within what limits? Excess up to a point — what point? — could be excused as youthful vigor. As in Furuhata’s youth, so in the early 1970s, with the Vietnam War a vivid symbol of all the world ills that needed to be set right — at all costs? Yes, said some, Furuhata’s new friend among them.

As the investigation proceeded and the internal purge became known, the suspect admitted his own participation in it. It seemed a case of lynch or be lynched. He appeared quietly, thoughtfully — not demonstratively — contrite. In the end he was sentenced to 20 years. He served 18, a model prisoner. What became of him after his release Furuhata does not say.

The Expo ’70 world’s fair opened in Osaka just two weeks before the Japan Airlines hijacking. Its slogan was “peace and prosperity for all mankind.” The expo was a great success but the optimism it projected seems absurd in retrospect, if it didn’t at the time. Probably it did. “Modern youth is in violent revolt against existing society,” wrote psychiatrist Takeo Doi in his 1971 bestseller “The Anatomy of Dependence.” He seems closer to the truth.

The revolt of youth — a global phenomenon — put society itself on trial, Doi argues. Youth was judge, jury and executioner. Society’s defense was feeble. Two world wars had stripped it of confidence. Authority had failed — authority of all kinds: governmental, pedagogical and perhaps above all paternal. Fathers themselves no longer believed in the old values they had once embodied and enforced. The result, in Doi’s terminology, was a “fatherless society.” In Japan, young people — even young radicals — tended in compensation to draw extraordinarily close to their mothers. This is the core of his famous concept of amae (dependence). It’s a strange coin indeed that can have two sides so seemingly at odds with one another: amae and revolutionary struggle to the death.

The police siege of Asama-Sanso unfolded — this not its least bizarre aspect — on live television. Equipment-laden TV crews gave the whole thing the feel of a “home drama,” the Japanese expression for something like a soap opera. A hostage’s life was at stake. Persuasion would trump force, if possible. It was not, quite. The fugitives’ parents were enlisted to plead for surrender — in vain. The heat was turned off; amplified noise made sleep impossible. Resistance continued. The police weapon of last resort was a crane with a wrecking ball that battered the building to pieces. Two policemen died, with numerous others wounded, in the climactic shootout that brought the curtain down at last — on Feb. 28 at 6:15 p.m.

Muta, the hostage, emerged, terrified but unharmed. “It’s cold, so cold,” she said — adding little more, then or later. One understands her silence. Some experiences can’t be shared. There’s nothing one can say about them — nothing intelligible, at least. Better say nothing.

Michael Hoffman’s latest book is “Cipangu, Golden Cipangu: Essays in Japanese History.”