“crushing civilian morale” is just a (poor) excuse for revenge bombing.
No.
Now we know Germany would have never surrendered, no matter how much it was bombed (save, of course, in case a bomb happened to kill Hitler, but at that time he spent most of his time inside a pretty tough bunker). At the time they didn't.
On the contrary, they knew that they had landed on the Italian homeland territory on July 9, that they had been hitting with increasing strength the Italian cities, that the campaign had further seen a crescendo between the landing and July 22 (hitting, first and foremost, Rome, but also Turin, Bologna, Cagliari, Foggia and other cities), and that - on July 25 the Fascist regime fell. The bombings continued in August, and in short order feelers were sent out by the new Italian government, seeking terms.
So a case could be made that the third most important Axis member had surrendered very quickly, once its armies had been defeated, part of its homeland invaded, and its civilians kept under bombing. And that would at least be somewhat indicative.
Interestingly for us, even if not a supporting argument in May 1945, is that the second most important Axis member would surrender with parts of its armies undefeated, no part of its homeland invaded, and its civilians kept under bombing, just some three months later.
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All that said, if you have built an extravagantly costly, gigantic airfleet, and you have ground troops that take casualties every day on the frontline, and you have doubts about the real effectiveness of that fleet, what do you do? Do you demand the PBI to finish the job at its own cost, while you send the flyboys on holiday?