I'm not sure why this post gets downvoted as it makes a really good point I see from time to time when discussing this matter: why drop the first nuke on heavil

I'm not sure why this post gets downvoted as it makes a really good point I see from time to time when discussing this matter: why drop the first nuke on heavily populated city? Dropping few on the biggest military bases or naval fleets, would be enough to scare the shit out of anyone. Why shooting civilians is considered a war crime, but deliberately nuking (Hiroshima Nagasaki) or mass bombing (Dresden, Tokyo, Iraq, Afghanistan etc.) them somehow makes it acceptable?