As someone who spent  2 YEARS at the DMZ as a soldier, I will tell everyone here that bombing North Korea won't work, unless Trump is ready to sacrifice millions of South and North Koreans.   

North Korea is not Iraq or Afganistan.   There is 2 millions of standing army confronting each other within the area that is similar to the size of lower mainland, BC, another 8 millions of reserves on both sides that will be ready within days.  

Also, bombing North Korea will simply result in China taking over North Korea, which is the worst outcome that I can think of.   In fact, that may be what Trump is thinking, to regain his own plunging popularity.   I know Americans do not care who owns North Korea.  Irresponsible.