Also true. Tokyo already had been leveled by firebomb raids (which in total killed more than both nuclear devices we later dropped). Without looking it up, as I recall the target in Hiroshima was the Japanese 7th Army HQ. A legit military target. But make no mistake, we weren't really concerned about civilian casualties. Plus, killing the Emperor would have (possibly) backfired on us, and he was in Tokyo.

At that point, we were more concerned about US casualties which would have resulted from an invasion of the Japanese home islands (conservative estimates are about 1M dead and wounded US personnel). We also likely saved millions of Japanese lives in the process, but that wasn't really part of the calculus. Looking back, it was just a happy side-effect (I've seen estimates of up to 10M Japanese dead and wounded if we had invaded).