The Fourth Geneva Convention was written in 1949, after the
war, mandating the protection of non-combatants around a war zone.
One would think that the United States’ moral compass would
have been pointing in that direction before we dropped the bombs
on Japan, and would have prevented the nuclear arms race since.
The Japanese legal system has found that the bombings were illegal
under international law at the time.
See also in The book of science:
Readings on wikipedia: