Sorry Guan, Bannon is not an oracle. Anyone can figure out that war on the Korean peninsula will not end well for either the North or the South. That is not the point. 
If Dear Leader decides to fire missiles at/toward Guam, or any US ally, there is no response left except a military one, regardless of the carnage that follows. Otherwise every dingbat leader from every hemisphere will decide that they can act with impunity against the US and its allies. 
Bannon should go see if "K Street" will hire him and pay for his incomplete advice.