the South is on standby in case of attack.
The North has frequently taken aggressive action in the 57 years since the armistice brought an end to the war that killed 350,000 Korean soldiers and 2.5 million Korean civilians, as well as 36,000 Americans, at least 200,000 Chinese and several thousand from other countries. The leadership of the communist state is irrational and no one wants to see them get away with the recent attack on the South's Yeonpyeong Island or last spring's attack on a naval ship.
However, instigating a nuclear war is certainly in no one's interest, and so the US and South Korea need to think long and hard before they provoke the North. The entire world has a stake in what happens there.
Image courtesy socioecohistory.wordpress.com.