Last Aug. 6 marked the 75th anniversary of the dropping of an atomic bomb on Hiroshima.

This year, Aug. 31 marks the 75th anniversary of "Hiroshima," the extraordinary exposé of the blast's lasting effects. The account, by journalist John Hersey, shocked the conscience of the world and changed the way the weapon was perceived — then, and now.

The 30,000-word story by the 32-year-old Hersey took up the entire issue of the New Yorker, a magazine then known more for humor and breezy features like "The Talk of the Town." But "Hiroshima" soon became the talk of the country, and soon the world, as it revealed the real impact of the weapon whose true death toll will never be known.

Hersey, an intrepid Time magazine war correspondent whose bravery in evacuating Marines from the Solomon Islands was recognized by the Pentagon, was just as gifted as a novelist as he was a journalist, winning the Pulitzer Prize in 1945 for his wartime novel "A Bell for Adano." But it was a different novel, Thornton Wilder's "The Bridge of San Luis Rey," which inspired Hersey to reduce the enormity of the devastation into intertwined stories of six survivors of the blast.

"It really emotionally involved people; it changed the topic from taboo into must-read," said Lesley M.M. Blume, whose book about Hersey's "Hiroshima" reads like a novel itself. Titled "Fallout: The Hiroshima Cover-up and the Reporter Who Revealed It to the World," it's a thoroughly reported and thoroughly readable account of how Hersey "reported to Americans the full, ghastly realities of atomic warfare in that city, featuring testimonies from six of the only humans in history to survive nuclear attack."

What Americans knew about atomic warfare was obscured by the White House and the Pentagon, and generally out of reporting reach to Japanese media and to a constricted (and at times too compliant) American press corps.

"It was just the same as getting a bigger gun than the other fellow had to win a war and that's what it was used for," said then-President Harry S. Truman. "Nothing else but an artillery weapon," he added, when it was of course the opposite, including the horrors of radiation poisoning, which Lt. Gen. Leslie R. Groves, head of the Manhattan Project, said could be a "very pleasant way to die."

The bomb's unimaginable scope led to some early errors, including from a young Europe-based United Press reporter who changed the account of an explosive equivalent from 20,000 tons of TNT to 20 tons. Clearly, "those French operators [had] made a mistake," Walter Cronkite said later.

Japanese journalists were banned from stories so they would not "disturb public tranquility." Many American correspondents were kept away from Hiroshima and Nagasaki altogether, or presented sanitized accounts by military officials. But Hersey, whose heroism perhaps gave him the brass' trust, got a two-week window to travel to Hiroshima. He used the fortnight well, writing an account that's reverberated for decades.

"Most people, not just in America but around the world, had not really comprehended the true implications of entering into the Atomic Age, largely because there wasn't that much known about the experimental weapons and their radioactive fallout and aftermath, and how the bomb keeps killing after detonation, and how it really only took one bomb at this point to destroy an entire city," said Blume.

"It was the first really important investigative work that alerted the world to the truth," Blume continued. "And in many ways, we need to revisit that work and be reminded again that not only do we [still] live in the Atomic Age, we live in what currently is the most perilous nuclear landscape ever, more so than in the depths of the Cold War."

In fact, last year the Bulletin of the Atomic Scientists set the Doomsday Clock at 100 seconds to midnight, as close to catastrophe as it has ever been, a designation that remained in 2021.

"Human beings can manage the dangers posed by modern technology, even in times of crisis," read a grave statement accompanying the Bulletin's announcement. "But if humanity is to avoid an existential catastrophe — one that would dwarf anything it has yet seen — national leaders must do a far better job of countering disinformation, heeding science, and cooperating to diminish global risks."

There's "a peculiar all-time low in awareness coincided with an all-time high of danger," Blume said. Part of the reason may be the other existential threats that the atomic scientists allude to.

Much of the public "doesn't think from day to day about the humanitarian consequences of the ever-growing risk of nuclear weapons," agreed Alicia Sanders-Zakre, the research policy coordinator of the International Campaign to Abolish Nuclear Weapons, which won the 2017 Nobel Peace Prize. "It's a difficult thing to have to grapple with."

Particularly when "We're now in the jaws of climate change and we're still in the jaws of a pandemic that keeps mutating," Blume said. "It's like, can people really take grappling with one more existential threat?"

Especially since information itself faces its own existential threat, as deliberate disinformation campaigns and technological and even ideological transformations threaten journalism's business model.

"We often think about what if Hersey's report had come out in a comparable environment today," Blume said. "It would be derided as fake news, right?"

But Hersey's searing reporting made it all too real. And even decades later, the blast's scars can be seen, from the iconic Atomic Bomb Dome to survivors themselves, as I learned interviewing three of them during a 2014 reporting trip to Japan. Their marred bodies, and lives, did not lead to hate, however, but to a dedication to educate the current world about nuclear warfare's horrors.

It's a commitment shared by Matsui Kazumi, Hiroshima's mayor, who told me back then that "Hiroshima is a city which has been pulling for the total abolition of nuclear weapons, which are an absolute evil." A realist about global proliferation pressures, the mayor took the long view — the really long view — when he said that the nuclear age "is such a short moment in the long history of human beings. When more policymakers can build a world on the foundation of mutual trust, then the world will move toward one without nuclear weapons."

Moving toward that world won't be easy. But it would be impossible without the truth, the kind Hersey revealed in "Hiroshima," which Blume said "has always been a really accessible and harrowing reminder of exactly what the stakes are in preventing nuclear disaster."

John Rash is a Star Tribune editorial writer and columnist. The Rash Report can be heard at 8:10 a.m. Fridays on WCCO Radio, 830-AM. On Twitter: @rashreport.