However, under the Just War Doctrine a case can be made for their use. Their use against Japan during World War II is a good case study.
I’d be interested in hearing that argued. Two consecutive Pontifs have argued that the existance of modern weapons of such scale, in of themselves, make just war in the Catholic tradition highly unlikely.
Consider, we interned civilians and then killed them in massive numbers. Both these are specifically prescribed in canon law in a just war. Yes, some people have tried to make the moral argument, but Popes are the supreme moral authority of our Church.
Let us compare these losses to those projected for Operation Downfall, the overall Allied plan for the invasion of Japan.
You are assuming that ground assault was the only alternative to an atomic attack. Numerous voices in the military were arguing for containment, since the Japanese lacked the domestic resources to sustain an significant war machine.
Some have argued that the casualty estimates for the invasion of Japan were inflated later by President Truman to justify the atomic bombing. However, consider that nearly 500,000 Purple Heart medals were manufactured in anticipation of the casualties resulting from the invasion of Japan.
Truman revised his own estimates, upwards, over time, in his recorded speeches and writing.
The 500,000 Purple hearts is true, which would equate to an expectation of 200,000 KIAs, which is massive. However, again, just war make a sharp distinction between combatants and non combatants.
As for the rest of the annecdote, I am not sure. I received two Purple Hearts, both are crimp brooch (post WW-II manufacture). So I suspect that the inventory was exhausted sometime in the mid-late 60’s. Also, both the Navy and Army have sent out ‘out of stock’ letters this year.
Finally, one of the posters stated that we only had two bombs. In fact the United States expected to have another atomic bomb ready for use in the third week of August 1945, with three more in September and a further three in October. There were enough bombs in the production pipe line that serious considerations were being made on where to drop them in terms of on targets to support an invasion, or targets that would assist in breaking the will of the Japanese government to continue the war.
I’m sorry, I can only go on the public and written memoirs of the individuals involved. I actually have had the good fortune of meeting several MProj participants (for example **** Feynman taught here in SoCal for many years), but never had an opportunity to discuss their experiences in detail and, of course, never pressed.