One wonders how many Americans would be aware of the horrific bombing of Hiroshima were it not for Christopher Nolan’s hit movie “Oppenheimer.”

Which recalls philosopher George Santayana’s observation that “those who do not remember the past are doomed to repeat it.”

Robert J. Oppenheimer was the lead scientist involved in the creation of the atomic bomb that was dropped over Hiroshima on August 6, 1945, 78 years ago, to get Japan to surrender in World War II.

While Oppenheimer never publicly regretted his role in the creation of the bomb, it haunted him for the rest of his life. The results were so devastating that Oppenheimer hoped that such bombs would not be used again.

Japan was doomed to defeat following the Battle of Midway June 4-7, 1942, and the bloody and costly U.S. invasion of the stepping stone islands that led to Japan, especially Iwo Jima and Okinawa. A defeated Germany surrendered May 8, 1945.

But the Japanese would not surrender.

The military zealots who controlled Japan were willing to fight to the death, or the death of civilians, which they had done in previous losing island battles, especially at Okinawa.

Even the firebombing of Tokyo with conventional bombs March 9-10, 1945, which killed 100,000 civilians and made a million more homeless, would not get the Japanese to surrender.

This meant that the U.S. would have to invade mainland Japan, something nobody wanted to do. The planned invasion, called Operation Downfall, estimated that it would cost the U.S. one million casualties. Japanese casualties, soldiers and civilians alike, would have come to millions more.

Hence, President Harry S. Truman decided to use the bomb.

So, on that hot August day, a U.S. B-29 dropped the first atomic bomb in history on Hiroshima, killing at least 120,000 civilians along with 20,000 Japanese soldiers. It wiped out the city.

Three days later a second of only the two atomic bombs on hand was dropped on Nagasaki, killing another 80,000 civilians.

The Japanese finally surrendered on August 15, 1945, and plans for an invasion were shelved.

What was lost in the aftermath of the two bombings was how the U.S. government sought to cover up the devasting destruction the bombs caused, particularly the spread of radiation, which previously had been unheard of.

Truman and government officials painted the bomb as a conventional weapon of war, and not the experimental, devasting, radiation-spreading weapon that it was.

Such news, it was feared, would tarnish the hard-fought moral ground the U.S. had achieved with its military victory over Nazi Germany and tyrannical Japan.

Americans at the time knew nothing about the atomic bomb or what it would do. It was created under the strictly secret World War II program called the Manhattan Project.

Army Gen. Leslie Groves headed the project. Oppenheimer, the “father” of the atomic bomb, headed its laboratory.

Following the bombings, U.S. occupation forces restricted reporters from entering Hiroshima and Nagasaki. Censors even killed their water-downed stories, and soon interest was lost.

Then, nine months later, along came young John Hersey, a reporter’s reporter who had covered the war in Europe.

As told by Leslie M. Blume, in her fine book “Fallout, The Hiroshima Cover-up and the Reporter who Revealed It to the World,” Hersey worked his way into Hiroshima. He was determined to find out what happened. It was still a mind-boggling, smoldering heavily restricted, forgotten city where people were still starving and dying from radiation.

Hersey found six rare survivors willing to talk about their ghastly experiences and the grim ordeal of others.

Hersey, to avoid military censorship, did not write a line in Japan but waited until he got back to New York.

There he wrote a 30,000-word story for The New Yorker titled “Hiroshima” which later became a book read around the world.

Hersey not only challenged the government’s narrative that the bomb was a conventional weapon but for the first time wrote about what radiation did to those lucky (or unlucky) enough to survive.   It was a horror show.

Hersey did what reporters are supposed to do.

The world took notice. No country has used a nuclear weapon since.

At least for now.

Peter Lucas is a veteran Massachusetts political reporter and columnist.