You can't say North Korea hasn't been sufficiently warned.

Following a test of a long-range ICBM that could hit the U.S. and the test of what many experts are concluding was a hydrogen bomb, Defense Secretary Mattis issued a severe warning to the Kim regime that if it threatened the U.S. or its allies, the U.S. would initiate a "massive military response."

Politico:

The Trump administration escalated its warnings to North Korea on Sunday, with Defense Secretary James Mattis warning of a "massive military response" and the potential to carry out "total annihilation" of the rogue state if it threatens to attack the United States and its allies.

The striking statement followed President Donald Trump's own warnings on Sunday in the wake of Pyongyang's latest major provocation, as he also upped pressure on South Korea and China to help contain North Korea's nuclear ambitions.

In a series of tweets, Trump accused South Korea of "appeasement" toward North Korea and warned that the United States is looking at halting trade with any country doing business with the repressive regime, a threat that is almost impossible to back up given American dependence on Chinese imports.

Mattis then delivered the military threat outside the West Wing on Sunday afternoon. "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," Mattis told reporters after meeting at the White House with Trump, Vice President Mike Pence and Marine Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff. "We are not looking to the total annihilation of a country, namely North Korea, but as I said, we have many options to do so."

The latest warnings from Trump and the Pentagon chief come after North Korea claimed earlier Sunday that it had detonated a hydrogen bomb that could be attached to an intercontinental missile capable of reaching the mainland United States.

It was not immediately clear whether Pyongyang had actually accomplished such a feat, which would be a major advancement in its nuclear capabilities, but the claim was nonetheless a significant act of aggression.

"North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States," Trump wrote on Twitter on Sunday morning. "North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success."

Is this a red line?  What constitutes a "threat"?  If Kim mouths off about targeting Guam again, is that a sufficient threat to unleash hell? 

Only Trump knows, which can be a good thing if we keep Kim guessing. 

Kim's actions may be louder than any threat he makes against the U.S. and our allies.  Word from South Korea is that the North is readying more missile tests.

North Korea appears to be preparing to launch a ballistic missile – possibly an ICBM, South Korean media reported Monday.

South Korea's Defense Ministry said North Korea appeared to be planning a future launch to show off its claimed ability to target the United States with nuclear weapons, though it was unclear when this might happen.

Chang Kyung-soo, an official with South Korea's Defense Ministry, told lawmakers that Seoul was seeing preparations in the North for an ICBM test but didn't provide details about how officials had reached that assessment.

Following U.S. warnings to North Korea of a "massive military response," South Korea on Monday fired missiles into the sea to simulate an attack on the North's main nuclear test site a day after Pyongyang detonated its largest ever nuclear test explosion.

Trump has clearly given up on China and perhaps even South Korea, whose efforts to rein in Kim's nuclear ambitions have met with no success. 

So here we are, on the brink of war, with no clue what Kim really wants or why he is continuing an apparently suicidal policy of threatening the U.S. with nuclear bombs.  It could be that Kim just wants to protect his family business, in which case the nukes are defensive.  Or he may want "respect" from the U.S. – whatever that means.  Or, as some in the Trump administration believe, Kim may be interested in blackmail:

But inside the Trump administration, many have begun to question the long-held assumption that his nuclear buildup is essentially defensive, an effort to keep the United States and its allies from finding the right moment to try to overthrow him.

Mr. Kim's real goal may be blackmail, they argue – the sort that would be possible as soon as North Korea can put Los Angeles or Chicago or New York at risk.

It may be splitting the United States away from two allies – Japan and South Korea – who wonder whether the United States would really protect them, and half-expect Mr. Trump to make good on his campaign threat that he might pull American troops from the Pacific.

Or it may be about making Mr. Kim a power broker, a man Mr. Trump and Xi Jinping – leaders of the two superpowers Mr. Kim is fixated on – must treat as an equal.

Maybe it is about all three.

And maybe it's none of that.  Perhaps Kim is reacting to internal North Korean politics rather than any external factors.  Just how much control does Kim exercise?  Is his power absolute, like his father's and grandfather's?  We have heard whispers over the last few years and tracked the execution of high-ranking officials that suggest Kim's actual position is more precarious than it appears to outsiders.  That is extremely bad news, if true.  Kim may feel compelled to go to war to save his own skin even if he knows the end result will be disastrous.

Here's the bottom line for Trump: North Korea cannot be allowed to possess the capability to strike the U.S. with nuclear tipped missiles.  Any and all action must be taken to prevent that scenario from becoming a reality.  Any other consideration – including the consequences of a war on the Korean peninsula – is secondary.