So thundered President Donald Trump last week. Unfortunately, neither China nor North Korea appeared intimidated by this presidential bombast or Trump's Tweets.

What would 'we will' actually entail? This clear threat makes us think seriously about what a second Korean War would be like. Memory of the bloody, indecisive first Koran War, 1950-53, which killed close to 3 million people, has faded. Few Americans have any idea how ferocious a conventional second Korean War could be. They are used to seeing Uncle Sam beat up small, nearly defenseless nations like Iraq, Libya or Syria that dare defy the Pax Americana.

The US could literally blow North Korea off the map using tactical nuclear weapons based in Japan, South Korea and at sea with the 7th Fleet. Or delivered by B-52 and B-1 bombers and cruise missiles. But this would cause clouds of lethal radiation and radioactive dust to blanket Japan, South Korea and heavily industrialized northeast China, including the capital, Beijing.