And it took a mere 21 days before this was used in anger.

Perhaps, on reflection, not quite long enough to consider the full implications of what effect this might have on a city full of civilians.

Unfortunately disregard for civillians had become commonplace by this time in history.

Hitler bombed Holland's cities and sent V2 rockets into London with no regard at all for civilians.

Japan did so even earlier in their war with China.

Our use of the atomic bomb precluded the Japanese version of it that they were working on in Korean based plants. Our military, including President Truman were convinced, after the horrific fighting on Iwo Jima, that we could have a million casualties if we invaded the mainland of Japan.

In context of the times it was a logical decision to use the weapon. I'm not sure how much good more warning would have done. Even after the second bomb the Japanese military did not want to surrender. However, in terms of morality, it would have provided a possible margin of comfort today.

You're speaking in 2008 terms...not 1945 terms. Depending on the degree to which Japanese civilians resisted the invasion, estimates ran into the millions for Allied casualties