So what will China do if each nation attacks the other at exactly the same moment?
N. Korea will say the US attacked first; the US will say N.Korea attacked first.
The difference in time may be less than 3 minutes.
The moment a rocket lifts off the ground will be detected by US satellite & radar positions.
It could trigger an immediate attack within minutes of launch.
The war crazies don't need an "attack", they can create one.
Afghanistan & Iraq did not attack the US, but one was created, none the less.