A second Korean War may go nuclear, but you don't want to do that. The prevailing winds will blow the fallout here to the U.S. within 3-5 days. The more you use, the more radioactive fallout will drift this way.
Also, you have to think about the neighbors (our allies and troops). I read that 100,000 American civilians live in and around Seoul. Same idea goes for Tokyo.
Choose the time with the weather being primary consideration. The wind does not blow all the time, and at least sometimes is very light. Strive for the total surprise. And the rest of the book.
Go Neutron.
Use antimatter .... I wouldn't be suprised if the US already had a few.
The NK Army is a rusted ill-used bunch of 1950-60 hardware....
they have been kept in underground bunkers for decades....
One JDAM in the mouth of a bunker renders it a tomb...
I sick of this " oh we have to be careful that they don';t attack us S4!t....
It's not 1954...
we can kick their a$$es in no time