As the Americans prepared to drop atomic bombs on the Japanese, the Japanese government was mobilizing the entire population of Japan to impose massive casualties on any Ameircan invasion.
According to the Japanese defensive plan Ketsu-Go, there were now precious few civilians in Japan:
The Japanese slogan in 1945:
“The sooner the Americans come, the better…One hundred million die proudly.” was not just for rhetorical effect. Based upon what the Americans had already seen in the Pacific, they could only interpret it literally. American planners for Operation Olympic, the invasion of Kyushu scheduled for November of 1945, were dismayed throughout July of 1945 to learn through intelligence intercepts that the Japanese were piling troops into Kyushu, the Japanese having guessed correctly that Kyushu would be the initial target for any invasion of the Home Islands. Fearing that an invasion would face a one-to-one troop ratio between attackers and defenders, it is possible that if the atomic bombs hadn’t been used, the invasion might have been cancelled, with continuing bombing and naval blockade until the Japanese were starved into submission. If such a strategy had worked, and there was no guarantee of it being successful, it is likely that surrender would have occurred only after several million Japanese had died from famine.
It should be noted that the prewar Orange Plans for war with Japan all assumed that the war would end with a blockade which would run about two years (recall Admiral Nimitz’ comment that U.S. planners foresaw everything but the kamikaze). The only reason why the U.S. was considering an invasion was that events in all theaters demonstrated that the U.S. had become very proficient in that difficult military art. By 1945 the U.S. had amphibious capabilities unimagined when the Orange plans were drawn up.
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Also, the decision had been made to employ poison gas against the Japanese. When Nagasaki was destroyed and the Japanese made no reply for days the decision was made to cancel any more attacks on cities and reserve nuclear weapons for tactical use. It was thought that these weapons would be in modern lingo “force multipliers” for the invading troops.
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Had the Japanese not surrendered, the U.S. would have seen many more VA hospitals built, including for the radiation casualties.
My decidedly inexpert take is that the Japanese sought to force a negotiated surrender by demonstrating they could take more casualties than we could. That is to say, because we couldn’t kill enough of them fast enough, our own mounting causualties would force us to accept their surrender on their terms before their casualites would force them to surrender unconditionally. What the atomic bombings demonstrated was the futility of that strategy.