Tinian Island is located just 1,500 miles from mainland Japan, which, during World War II, made it an ideal launching pad for American B-29 Superfortress bombers against Japan. Therefore, after American forces captured Tinian in August of 1944, the U.S. Army Corps of Engineers turned an island that had been mostly sugarcane into the world’s then largest airport.

A year later, Army personnel hydraulically lifted an odd-shaped weapon — called “Little Boy,” and described by one crew member as “an elongated trashcan with fins” — into the belly of a B-29 Superfortress, Enola Gay, named after the mother of its lead pilot, Colonel Paul Tibbets.

At midnight the flight crew received its final briefing, having learned that the previous months-long training was to result in dropping the most explosive bomb in history, an atomic bomb with power equal to 18,000 tons of TNT. Crew members were given dark glasses to protect them from a blast described as “a new sun being born,” and then, after a briefing by the weatherman who told them to expect a smooth flight, an Army chaplain blessed them, asking the Almighty to protect those “who carry the battle to our enemies.” Earlier the crew was shown photographs of possible targets, the primary one being Hiroshima, with Kokura and Nagasaki as secondary.

At around 2:40 am, August 6, 1945, after Tibbetts had started the bomber’s four engines, it was airborne, and around 8 pm (Hiroshima time), the plane approached Hiroshima. “I see it!” shouted Thomas Ferebee, the Enola Gay’s bombardier, taking aim in his bombsight and letting the bomb drop.

“No one knew what to expect,” Copilot Robert Lewis wrote in his logbook, while Tibbets immediately pulled the plane into a turn away from the target. Suddenly the light “of a new sun being born” filled the plane and the first shock wave hit. A second shock wave hit moments later, after which the plane was steady, and the crew was free to observe the damage the bomb had done.

Their reaction was mixed as they watched what Tibbets called a “terrible and incredibly tall” mushroom cloud climb the sky, knowing it had instantly killed tens of thousands of Japanese military personnel, but also civilians. “Thank God the war is over and I don’t have to get shot at anymore. I can go home!” shouted navigator Theodore Van Kirk.

In contrast, Copilot Lewis thought, “My God, what have we done?”

What they had done, as Van Kirk exclaimed, was end the war, but also, as Lewis feared, ushered in the Atomic Age, in which any all-out war waged using these weapons had the potential to wipe the human race off the face of the Earth.

Bruce G. Kauffmann’s email address is bruce@historylessons.net @BruceKauffmann.