Bill Whittle's 17 minute segment in Hiroshima/Nagasaki is well worth watching.
Not only does it tally with what I was toght in school over 30 years ago, it also tallies perfectly with the histories I have read since then such as Tibbets' (pilot of the Enola Gay) bio.
Warnings? Military targets? A protracted enemy society? Whittle puts paid to it all. Make 17 minutes in your day to get some wonderful detail on an important historical event.