@sebastian You are probably right about the level of German civilian casualties but then all of these numbers are a little suspect. I have seen numbers between 30,000 and 300,00 both for the bombing of Dresden and the Rape of Nanking. I think it is important to talk about these things and allow historians to do their research and present their findings. Best if politicians stay out of it.
The so-called Three All campaign of the Japanese Army in Northern China in 1941 is supposed to have caused the death of 2.7 million civilians according to research by one Japanese group of academics but this is challenged by others. After threats from right wing organizations in Japan, publication of this information was suspended. Note that the Japanese Prime Minister now goes around saying that depending on how we define the word “invasion”, Japan did not invade China. Nice.
The principle to me is that civilian casualties whether by nuclear bomb, or by the deliberate killing of every man, woman and child in a town, are equally tragic. Unfortunately this kind of behaviour has been going on since the beginning of history, it is just the means of destruction have escalated. The scale of this slaughter matters, of course, but so does the motivation.
In my view, and with hindsight, and not being a strategist of any kind, the bombing of German cities was more an act of revenge than a useful military operation. The wanton slaughter perpetrated on Eastern European civilian populations on a large scale by the German Army served no strategic purpose, on the contrary. It was simply indicative of the arrogance and callousness of the German army, high command and ordinary soldiers. The same can be said of much of the brutality of the Japanese army in China and elsewhere. But then this kind of behaviour is very human, in Rwanda they used machetes, in Europe they used muskets, and Genghis Khan used swords or whatever, and on and on.
The bombing of Hiroshima and Nagasaki served a real strategic purpose. If we consider the fanatical “never surrender” attitude of the Japanese army, dying rather than being taken prisoner, civilians throwing themselves off cliffs rather than surrendering on Pacific islands, Japanese soldiers waving a white flag in order to entice American soldiers and then kill a few more of them, it was a fair assumption that resistance on the main islands would be ferocious. The two nuclear explosions and perhaps also the entrance of the Soviet Union into the Pacific War finally convinced the Japanese that resistance was futile.
As for Pearl Harbour, what strikes me the most there is not the scale of destruction but the scale of arrogance and foolishness of the Japanese military, expecting that the US would not fight back. It only took 6 months, until Midway, before the writing was on the wall.