Thanks for the responses, I was expecting that they would go somewhere along those lines.
As I said, I do realize that those were different times, even if I do have trouble excusing the massive terror bombings of civilian targets just because it was the style of the day... just as much as I don't approve of what the Germans were up to against the civilians of the East Front on the basis of "well, at the time the Germans thought it was okey to do that, duh!"
When it comes to liberating Japan's conquests in Asia, it's all fine with me if this was indeed the motivation behind not stopping before you've got total, formal surrender. From a more selfish perspective... if I was only considering the benefit of my own nation in that situation, it would probably be cheaper in overall life and treasure to just bomb their industries, sink their navy and not bother with firebombing/nuking their civilians or invading their islands. Besides, by isolating their islands from the rest of the empire you'd cripple their capacity to harm their conquered territories as well...
I would simply not have bothered. They could have screamed that it's "just a flesh wound" all they'd have wanted... at some point they would have had to accept the facts. I have a hard time believing that the Japanese would have been able or willing to bounce back and mount a counterstrike had they been contained as I suggest.
Would a blockade have starved them? Who knows. Maybe they would have surrendered when things started to look dire enough.
Of course one can make the claim that your patriotism demands the complete surrender... okey, if it does, then I suppose it does. My patriotism does not demand disproportionate measures against civilians in the name of revenge. Steviejay, I would think that the firebombing of Tokyo that killed some 100,000 counts as an example of a "mass slaughter of civilians" that you're not aware of. Then of course there are the nukes...
Now... if the options are either to cause even more casualties (how many more hundreds of thousands?) while waiting for the surrender that might not be forthcoming because of the leadership's stubbornness, or to launch an invasion of the islands that would kill even more people(!), I would really, really prefer to stand down, in particular if I am not that afraid of my enemy anymore. Just call me a coward...
To the Germany example... well, there you at least had solid ground offensives going on both sides that were going to reach Berlin eventually, and you had proper military units to fight against along the way. War against a military is fair game, no complaints there. Of course here too we can start discussing whether for example the bombing of Dresden helped "weaken the German resolve"... it didn't really work with the Brits -- quite the contrary, really -- is there reason to believe it worked with the Germans?
Anyway, moralizing is always too easy in hindsight... I just like to see things the other way around too.