It also saved the lives of Japanese civilians elsewhere in the country.
From the movie “Crimson Tide”: (following a discussion about the merits (or not) about dropping the bombs)
RAMSEY: Did you think it was a mistake, Mr. Hunter?
RAMSEY: Did you think it was a mistake, dropping the bomb on Hiroshima and Nagasaki?
HUNTER: Well, if I thought that, sir, I wouldn’t be here.
RAMSEY: Interesting, the way you put that.
HUNTER: How’d I put it, sir?
RAMSEY: (pause) Very carefully. (other men chuckle). You qualify your remarks. Someone asks me if we should have dropped the bomb, a simple “Yes. By all means, Sir. Drop that f-—er. Twice!”