Thanks to an e-mail from a reader who wishes to remain anonymous, I was led to a 35-minute propaganda/documentary film called 'The Last Bomb'. It was shot in 1945 by US Army Air Force personnel, and shows a raid on Japan by B-29 Superfortress aircraft based in the Mariana Islands. It was nominated for an Academy Award in the same year, in the category 'Best Documentary Feature', but did not win the Oscar.
If you have time to watch it (as I said, it's 35 minutes long), I've embedded it below - or you can download it from its home page at the Internet Archive. It's in the public domain, so there are no copyright issues involved.
That's a remarkable piece of history on film. My sincere thanks to the reader who brought it to my attention. I hope you all enjoy it as much as I did.