Unless you’ve sworn off news over the three-day weekend—and you obviously haven’t or you wouldn’t be here—you know that North Korea tested another nuclear weapon Sunday, its sixth such test. This time it was almost certainly not a fission bomb like those dropped in World War II, but rather a fusion weapon, the kind that the other eight nuclear nations have in their arsenals. 

The U.S. Geological Survey detected a 6.3-magnitude earthquake at North Korea’s Punggye-ri testing site, noon local time. Experts said that this was evidence that Pyongyang had detonated a hydrogen bomb with an estimated explosive yield of 100 kilotons. The atomic bomb dropped on Hiroshima in August 1945 was estimated at about 15 kilotons and killed 100,000 people in a flash, with thousands of subsequent fatalities from radiation sickness and cancers. 

North Korea later said that it had, indeed, conducted a test of a hydrogen bomb small enough to install on the intercontinental ballistic missiles it has tested recently. 

In response to the test, Pr*sident Donald Trump tweeted:

Trump did not say what would work. But Secretary of Defense James Mattis announced after briefing Trump Sunday:

"Any threat to the United States or its territories—including Guam—or our allies will be met with a massive military response, a response both effective and overwhelming." [...]

However, he said the hope was for denuclearisation, "because we are not looking to the total annihilation of a country, namely North Korea".

Not looking for total annihilation? Well, that’s somewhat encouraging.

In a prepared statement, South Korean President Moon Jae-in responded:

“South Korea is a country that experienced a fratricidal war. The destruction of war should not be repeated in this land. We will not give up and will continue to push for the denuclearization of the Korean Peninsula through peaceful means working together with our allies.”

Anna Fifield at The Washington Post writes

South Korea’s response overall to Trump’s recent pronouncements has been much more muted than its past explosions against its protector — a sign that they know Trump is a different kind of president.

“They think they’re dealing with an unreasonable partner and complaining about it isn’t going to help — in fact, it might make it worse,” said David Straub, a former State Department official who dealt with both Koreas and recently published a book about anti-Americanism in South Korea.

“Opinion polls show South Koreans have one of the lowest rates of regard for Trump in the world and they don’t consider him to be a reasonable person,” Straub said. “In fact, they worry he’s kind of nuts, but they still want the alliance.”

Kind of nuts. Just the sort of leader needed when the possibility of slinging nukes is at issue.

The reality here is obvious. Unless Kim really is irrational—something many speculative commentators in the media say he is but that many Western experts on North Korea do not believe—the likelihood that he would launch a nuclear attack on the United States, or even on Japan or South Korea, seems very small. No nation has dropped a nuke in anger since the U.S. obliterated Nagasaki 72 years ago. And over the past 60 years, the reason for that is obvious. The ensuing slaughter would be immense.

If Kim did attack, however, which U.S. official would dare to stand in the way of what definitely would amount to total annihilation of North Korea and millions of its people? Despite his ruthlessness, and his chest-pounding bravado over his nation’s nuclear arsenal, Kim cannot be unaware of this.