[thombat]

Terror and fear was already present in greater abundance:

https://en.wikipedia.org/wiki/Bombing_of_Tokyo#Operation_Mee...

yet five months later Japan maintained an external persona of implacable resistance. For example the subsequent invasion of the Okinawa islands resulted in over 14,000 American deaths. It was reasonable to apprehend that the invasion of the far bigger Japanese home islands would be far more lethal, also for the Japanese population.

In the Tokyo raid 96 American airmen were killed, despite the only effective defence being poorly co-ordinated anti-aircraft fire. Given a weapon that claimed the potential to end the war without further American losses it seems unrealistic to expect it not to be used.