[Captain Kirk]

No it wasn't. The Japanese insisted on the condition of keeping the emperor and, after much cabinet debate, Truman agreed. A surrender would not have occured, at least at that time, had not Truman agreed. Truman could have had the same deal earlier (and avoided the needless INTENTIONAL mass death of babies, little out ladies, and Japanese Christians) had he pursued this earlier.

[Gaffer]

I think you give too much single-minded emphasis to the Japanese power structure at that time in its history. The military (Army), the Navy (somewhat) were at odds with its political segment - to the point of near rebellion.

You can argue whether the insistence of keeping an emporer and accepting that condition made it unnecessary to bomb them was the key, but I contend that the national psyche of war and dominance that overly influenced the population could only be subjugated one way, and that was total defeat - the best and most expedient way at that time was the A-bomb.