Wikipedia claims Hiroshima was saved for atomic bombing, about a month ahead:
> On 3 July, the Joint Chiefs of Staff placed (Hiroshima) off limits to bombers, along with Kokura, Niigata and Kyoto
Nagasaki was not explicitly saved, but was just a difficult target to hit:
> Nagasaki had been spared from firebombing because its geography made it difficult to locate at night with AN/APQ-13 radar.
> Unlike the other target cities, Nagasaki had not been placed off limits to bombers by the Joint Chiefs of Staff's 3 July directive, and was bombed on a small scale five times.
Anyone with better sources could please fill out the Wikipedia article some more:
July 3 was one month prior to the nuclear bomb dropping. By that time, B-29 bombing raids with conventional bombs had been operating since 1944. Further, the fact that they had to order it to be preserved on July 3 implies that it hadn't been saved until that point. So, Hiroshima was saved for a month, but only after it had been an equally viable target for the prior several months to a year.
In the context of a bombing campaign for a war, yes, a month and a year are a massive difference. And while they hadn't done the Trinity test, you don't do a test like Trinity until you're pretty damn sure it will work. Apparently, when you're ready to do the test you're also ready to start picking targets.
Saving Hiroshima and Nagasaki to be proving grounds for the scale of destruction is horrifying. However, all war is a series of horrifying and unnecessary events. Pointing out that some of them near the end were also horrifying is just not a very compelling criticism. It's not out of character for what happened during the rest of the war.
