After 71 years, hardly anyone remembers, and in a few more, no one will. In an instant, 70,000 people were incinerated, and a hundred thousand more would die, slowly, agonizingly, in the months that followed, their blood poisoned, their souls blackened, their ashes floating on the hot breath of August.

For years afterwards, hardly anyone even talked about what happened when the Enola Gay dropped Little Boy onto the Japanese city of Hiroshima. The war was over, the world had awoken from its long night of tyranny, butchery and madness. No matter that it took the single most monstrous act in the history of warfare to end it.

We had to do it. We were not taking lives, we were saving them. We are the land of the free and the brave. In God we trust, our wars are just. That’s what our national anthem says, in the fourth verse that no one ever sings. (Nevermind the third which says that “no refuge could save the hireling and slave from the terror of flight or the gloom of the grave.”) When you are fighting great evil, sometimes you must use Hell’s own weapons. That’s what we told ourselves.

President Kennedy, in a speech to the United Nations, spoke of nuclear weapons with regret: “Today, every inhabitant of this planet must contemplate the day when this planet may no longer be habitable. Every man, woman, and child lives under a nuclear sword of Damocles, hanging by the slenderest of threads, capable of being cut at any moment by accident or miscalculation or by madness.”

We have learned to live under this Sword by employing a collective amnesia about the only time nuclear weapons have ever been used. But this week that amnesia was torn asunder when we learned that the man who may very well be our next President will not rule out using them again. Donald Trump is not alone in that regard: every American President since Truman has had to live with that reality. The nuclear genie cannot be stuffed back into the bottle. It is only the fact of mutually assured destruction which has reined in the impulse to turn our enemies’ cities into radioactive rubble. For we know that our children too, will die in that act. The world will die. So, we keep the safety on for now, even as we caress the trigger.

We can debate whether or not Harry Truman’s decision to use nuclear weapons was for a greater good or was only a tragedy of unspeakable enormity. They were only used once, and a war ended because of them or in spite of them. Since August 6, 1945, even in the face of global proliferation, we have kept that weapon holstered. But what if a madman picks up the gun? What then? And what if he is our madman?