On August 6th, in 1945, the world saw the first use of atomic weapons against human targets. On this day 63 years ago, humanity lost its nuclear virginity. Until the end of time we will be a species that has used fission bombs in anger.
Time has passed, and we still haven't blown up our world, despite a close call or two. Which makes it difficult to criticize the decision - would things still have turned out all right, if anyone had chosen differently, anywhere along the way?
Maybe we needed to see the ruins, of the city and the people.
Maybe we didn't.
There's an ongoing debate - and no, it is not a settled issue - over whether the Japanese would have surrendered without the Bomb. But I would not have dropped the Bomb even to save the lives of American soldiers, because I would have wanted to preserve that world where atomic weapons had never been used - to not cross that line. I don't know about history to this point; but the world would be safer now, I think, today, if no one had ever used atomic weapons in war, and the idea was not considered suitable for polite discussion.
I'm not saying it was wrong. I don't know for certain that it was wrong. I wouldn't have thought that humanity could make it this far without using atomic weapons again. All I can say is that if it had been me, I wouldn't have done it.
I'm amazed how many comments are arguing that World War II contained much worse catastrophes than Hiroshima. Of course it did. Hiroshima isn't even in the top 10, if you consider only the direct effects of a small fission weapon. I've usually seen the total death toll from WWII estimated around 50 million lives, and Hiroshima and Nagasaki combined, on the order of 200,000 lives.
I have no reason to think it hurts more to die in a nuclear firestorm than a chemical firestorm, but chemical firestorms don't scale up the way nuclear firestorms do.
The issue is whether establishing a precedent for using nuclear weapons, increased the probability of their future usage, potentially costing billions of lives.
I am amazed at how many commenters entirely ignore this issue, which was explicitly the whole focus of my original post.
This says something about the problems humanity faces in recognizing and handling its global catastrophic risks. Apparently many people just don't have a mental bin for global risks to humanity, only counting up the casualties to their own tribe and country. Either that or they're just short-term thinkers. They can ask how much use of the Bomb helped America, or even how much use of the Bomb hurt (or helped) Japan, but not how use of the Bomb affected the probability of nuclear war for the next 63 years and beyond.
I can tell you that I've spoken to nuclear proliferation specialists and they say that perceived hypocrisy by America is a major problem in convincing other nations not to develop nuclear weapons. Now we don't know what those nations would be saying, if no one had ever used nuclear weapons. Maybe they would just find a different excuse. But at least to first order, it looks like Hiroshima had knock-on effects on nuclear proliferation and nuclear diplomacy.
If we put the cost of a nuclear war at 1 billion lives, then it only takes a 0.0002 positive probability effect on nuclear war to outweigh the direct loss of life at Hiroshima, and only a 0.05 positive probability effect on nuclear war to outweigh WWII, integrated over branches.