I talk in more (somewhat ramble-y) detail here [0], but I think I can put a more succinct version of the anti argument here, the main argument is that to morally justify the extreme act dropping atomic bombs on those cities requires an extreme set of justifications to the level of "it was the only option short of a bloody millions dead between both sides home island invasion" that history doesn't necessarily support.
The core thrust that undermines the this or that between bombs and traditional invasion justification for dropping the bombs is that a) the Emperor was already exploring possible peace deals and b) ultimately the Emperor was able to override the extreme militarists in the war council and accept the peace after the bombs. A lot of the pro-moral-bomb argument presupposes that the shock and awe of the atomic bombs were a prerequisite for the change in stance and that anything short of a full invasion of the home islands would not achieve shift large enough to get to a peace deal. (and that to achieve that impact required them to be used on a city)
Ultimately I think (and I know this is extremely hard to prove ahistorically) a naval blockade and shelling/arial campaign that devastated what little military might Japan had left would have lead to the same shift as the bombs and that the casualties from that would be lower or at least less morally weighted as the intentional atomic bombing of Hiroshima and Nagasaki. When that shift would happen and how to weigh the deaths morally are going to vary a lot from person to person though and I accept that.
> Even after all this, hardline military officers attempted a violent military coup to destroy the Emperor's recorded surrender broadcast and keep the war going.
A coup that ultimately fails though. I don't think anyone really argues that there weren't fanatical elements remaining even after the bombs were dropped. Their existence doesn't mean peace required the bombs however, the big question is what were the conditions that would reduce their power to the point the peace could be accepted. We have one example in the bombing but that doesn't mean that was the only option.
[0] https://news.ycombinator.com/item?id=49757977
The core thrust that undermines the this or that between bombs and traditional invasion justification for dropping the bombs is that a) the Emperor was already exploring possible peace deals and b) ultimately the Emperor was able to override the extreme militarists in the war council and accept the peace after the bombs. A lot of the pro-moral-bomb argument presupposes that the shock and awe of the atomic bombs were a prerequisite for the change in stance and that anything short of a full invasion of the home islands would not achieve shift large enough to get to a peace deal. (and that to achieve that impact required them to be used on a city)
Ultimately I think (and I know this is extremely hard to prove ahistorically) a naval blockade and shelling/arial campaign that devastated what little military might Japan had left would have lead to the same shift as the bombs and that the casualties from that would be lower or at least less morally weighted as the intentional atomic bombing of Hiroshima and Nagasaki. When that shift would happen and how to weigh the deaths morally are going to vary a lot from person to person though and I accept that.
> Even after all this, hardline military officers attempted a violent military coup to destroy the Emperor's recorded surrender broadcast and keep the war going.
A coup that ultimately fails though. I don't think anyone really argues that there weren't fanatical elements remaining even after the bombs were dropped. Their existence doesn't mean peace required the bombs however, the big question is what were the conditions that would reduce their power to the point the peace could be accepted. We have one example in the bombing but that doesn't mean that was the only option.
[0] https://news.ycombinator.com/item?id=49757977