As a child learning American history (I think it's part of something called 'civics' now for reasons surpassing my understanding) I was always struck how World War II began for America with airplanes. Actually with swarms of planes, low over the horizon, out of the sun over Pearl Harbor Naval Station in Hawaii.
Today, seventy-one years ago, from the belly of the Enola Gay, a B-29 Super-Fortress, the US Army Air Corps dropped the world's first atomic weapon on the Japanese city of Hiroshima and while a second bomb was dropped a matter of days later on Nagasaki to 'seal the deal' the harnessing of the atom into such a terrible weapon of destruction delivered by an airplane on this day all those years ago effectively ended the second World War.
As a fan of symmetry, even as a wee slip of a lad, I was struck by the bookend effect of beginnings and endings. I've read accounts where some of those who worked on the devices were relieved that the first actual use did not trigger, as they had feared, an unfettered chain reaction they could not stop, destroying the planet.
Except, as I look around a somewhat beaten and battered world that's lived in the Atomic Age (and in dread of its consequences) even longer than I have been on earth, I wonder about that road to perdition, the slippery slope and the law of unintended consequences.