https://en.m.wikipedia.org/wiki/The_Ones_Who_Walk_Away_from_...
Kant never had to choose between 225,000 dead (Hiroshima + Nagasaki) or 70,000,000 (the rest of the population who showed every sign of willingness to fight to the last child).
It’s not my point though. Regardless of the actual trade in lives and human suffering between the two alternatives, a deontological viewpoint judges the rightness of an action by the action itself - no matter the outcome.
So that’s my point. The bombing of civilians (whatever the prevailing norms, and no matter the consequences), is always wrong, and can never be justified on the grounds of “it shortened the war“ or “it would have saved millions of lives”.
However, it’s not a simple and clear cut argument, and perhaps it can be justified in other ways. I reject the utilitarian arguments, but I’m open to considering other justifications.
The real world has many more real variables and tradeoffs than any ethical system could reasonably account for even abstractly. The systems provide a surface to bounce new cases off of, but IMO if an ethical system says it's preferable to pick near-certain death of say 1 million people (a mere 1.4% hypothetical casualty rate) over the certain death of 250,000 people, it should very obviously be discarded for that case.
No ethical system, including Kantian, says it’s better to pick a million dead over 250k. Kant says “you can’t kill 250000 people to save a million, and call yourself righteous”. A man can sell his soul to save his family but the price must be paid.
The common justification that I have read is that the bombings shortened what would have otherwise been a protracted defeat, potentially saving many more lives than were taken. A Utilitarian argument. However, if we were to take a Kantian point of view, the bombed civilians were used as an “ends” to achieve victory. Or more simply, an immoral act can never be justified, whatever the outcome.
So which is right? I enjoyed a recent Star Trek episode that examined the Utilitarian philosophy taken to an extreme (spoilers follow). In it an advanced utopian society is powered by the suffering of one child, chosen before birth. The joy and happiness of millions, at the expense of one innocent. Utilitarian philosophy (and modern economic theory), would call this an obviously acceptable trade-off, but Kant would argue that it is immoral as a person can never be used as an ends.
In the real world, we saw this argument play out in regards to whether the torture of terrorists was acceptable if it meant the extraction of information that would save lives.
Personally, I am of the Kantian view point, and I think the nuclear bombing of the two Japanese cities can never, and should never, be justified as moral acts.