About the atomic bombing of Hiroshima and Nagasaki, much discussed again lately, as called for, on the anniversaries, if that's the right term, of those events, some thoughts:
The atomic bombings were world-historically unspeakable events, thus far, thankfully, one (rather two) of a kind.
This is from John Keegan's, "The Second World War", Keegan being the late English, much esteemed military historian:
On 9 March  Bomber Command attacked Tokyo with 325 aircraft armed exclusively with incendiaries, flying at low altitude under cover of darkness. In a few minutes of bombing the city centre took fire and by morning 16 square miles had been consumed. . . The casualty list recorded 89,000 dead. . . by mid-June Japan's five other largest industrial centres had been devastated — Nagoya, Kobe, Osaka, Yokohama and Kawasaki — 260,000 people had been killed. . . by July, 60 per cent of the ground area of the country's sixty larger cities and towns had been burnt out. As MacArthur and other military hardheads had argued, however, the devastation did not seem to deflect the Japanese government from its commitment to continuing the war. p 576
The fire bombings of Japanese cities were no less ruinous than what came after:
It was the uranium 235 version of [the] atomic bomb that the B-29 Enola Gay dropped over Hiroshima on the morning of 6 August, 1945; a few hours later, while 78,000 people lay dead or dying in the ruins, a White House statement called on the Japanese to surrender. . . No word being received, on 9 August another B-29 flew from Tinian to bomb the city of Nagasaki, killing 25,000.. . . p 584
Let me venture this: had Japan mastered nuclear technology, it would not have hesitated to drop atomic bombs — on China, the Soviet Union, the United States.
Why didn't it master such technology — and, for that matter, why didn't the Nazis, who craved and fantasized super-weapons?
Lack of industrial capacity, that industrial power being unique to the United States.
(Keegan again: "In the final enumeration of Hitler's mistakes in waging the Second World War, his decision to contest the issue with the power of the American economy may well come to stand first.")
Lack, too, of the necessary science. In the case of Germany, which had the scientific basis, many of the scientists necessary were the very Jewish physicists who fled Hitler.
World War was unthinkable for the Chinese Japan murdered by the Japanese en masse. (I wonder how many Chinese feel Japan should have been spared atomic bombs.)
I'll stop here, except to say, World War II was and should be unthinkable, except it can't be unthinkable — can't escape being thought about — just because it happened.