It was grim, but Japan, surely, would have used the bomb had they harnessed the technology first.
Without a doubt.
But, of course, Japan was focusing its resources on biological warfare agents, which were tested on POWs, and Chinese men, women and children and analyzed with vivisection experiments.
Don’t want nothing, don’t start nothing.
I believe Japan was getting ready to drop a “dirty bomb” on San Francisco.
I believe they also had war gases prepared to use on our invasion forces. The civilian casualties from that alone would have been very high.