[IowaStatePhiPsi]

re: region affect: obviously the bombs at Hiroshima & Nagasaki didnt destroy all of Japan or leave it coated in radiation. You only use the bombs on centers of dense population- not on the empty desert.

re: nuking DPRK: Well, I assume that China will take offense at that and send things towards us- primarily our military locations in SE Asia, maybe use it as a factor to declare war and take Taiwan back (for "homeland security purposes"). Depending on the damage of the first nuke, DPRK may be able to launch whatever it has towards Japan and/or ROK, but who knows what their accuracy would be? I doubt they could target an American military installation outside of ROK very well.