And their leadership had shown that they were willing to sacrifice all their civilians (100MM) if it saved their emperor-military system.
You can argue that it was a better alternative than an invasion or some other strategy, sure. But the reality is that the civilians, who couldn't go anywhere else, were killed, en masse, by bombs dropped by the US.
Japan had factories, of course, but a lot of the ancillary things to war, like uniforms, etc., were made in people's homes, rice and so on was reserved for soldiers and the surplus was then distributed in the communities. The economy was massively focused on furthering the war effort --even moreso than the US.
I think you need to listen and watch Japanese programming from that era to get the picture of how involved the civilian population was in the war effort.
War is not fine. Dropping bombs is not fine. But they would have. They had plans to build bombs for exactly that, to drop on US cities. they also had plans to engage in biological warfare on US soil. So, yes, they would have. Japan was indiscriminate when they attacked China. If they had had the ability to reach US soil, they would have waged the same here, no doubt about it at all.
Germany would have done the same too. I mean, those guys were not fooling around. Do you think the US, the UK and the SU should have taken it easy with Germany because eventually we would have won a "kinder" (no pun intended) war?
We can use phrases like "neutralise the enemy", but the reality is, hundreds of thousands of civilians were killed in order to defeat the enemy.
In the end, would have the Japanese population suffered more with a conventional ground war vs firebombings or atomic bombings? I believe the consensus is stopping the war as quickly as possible spared the population the worst of it.
In great wars like this the distinction between military and civilian is tenuous. Japan, like Germany, was thoroughly a martial economy.
If you start a fire, don't complain later you got burnt.
Japanese civilians in battle zones routinely walked up to Allied soldiers with grenades to blow them up. They threw themselves off cliffs rather then surrender.
We still have this concept that somehow the German and Japanese citizens where not involved in the actions of their governments. It's as much of a myth as the myth of a "Clean Wehrmacht"
And about civilians attacking Allied soldiers, do you have references for people in Tokyo, Hiroshima or Nagasaki doing it?
The Battle of Okinawa seems like an example - Both willingly and by coercion, a large portion of the civilian population was sent into the battle to die with minimal training or equipment, including children.
Is there some reason to think the populations of those cities would have acted differently if the front lines came to them at that time?
They literally disassembled their factories in many cases, and put equipment into people's houses. The broke the factories into workshops, which where highly inefficient. The Japanese believed this would make them resistant to bombing, but also scale well since they didn't have to centralize at single sites. (the exact opposite of Fordism). They were incorrect on both counts.
And no, there are no documented records of people in Tokyo, Nagasaki and Hiroshima doing it - killing people tends to make them unable to engage in further violence (though it may encourage societies to further violence). but there are records in Okinawa, and in virtually every other sizable Japanese population engaging in violence.
That even includes in Hawaii. See the Nihau incident.
About the bombings, the targeted bombing wasn't working very well because of weather, so they decided to obliterate cities with incendiary bombs, civilians and all.
But returning to mass murdering civilians to advance military objectives: what would you think of the Soviet Union destroying with atomic weapons Munich and Frankfurt, to force Hitler to an unconditional surrender? Would reducing the deaths of soviet soldiers be a good justification?
Your point is good - that's a isolated event - but it was a isolated event that was taken into account in the military actions that followed.
And yes. If the soviet union had destroyed munich and frankfurt (Frankfurt was the transportation hub of the western front) to force Hitler to surrender it would have been justified. To draw the full conclusion - it would not have been justified to bomb Geneva (since it wasn't a military target).
And frankly, bombing Frankfurt would have been far far less heinous then what the Red Army did to East Prussia, which could not be justified. The difference there is that the soviets had already overrun Prussia when they committed their war atrocities. Likewise, what US solders did to German PoW in more isolated circumstances.