The underground blast was by far North Korea’s most powerful ever. Though it was far from clear that the North had set off a hydrogen bomb, as it claimed, the explosion caused tremors that were felt in South Korea and China. Experts estimated that the blast was four to sixteen times more powerful than any the North had set off before, with far more destructive power than the bombs dropped on the Japanese cities of Hiroshima and Nagasaki during World War II.
.. Mr. Trump hinted at one extreme option: In a Twitter post just before he met his generals, he said that “the United States is considering, in addition to other options, stopping all trade with any country doing business with North Korea.’’
.. Taken literally, such a policy would be tantamount to demanding a stoppage of any Chinese oil to North Korea, essentially an attempt to freeze out the country this winter and bring whatever industry it has to a halt.
.. The Chinese would almost certainly balk; they have never been willing to take steps that might lead to the collapse of the North Korean regime, no matter how dangerous its behavior, for fear that South Korean and American troops would occupy the country and move directly to the Chinese border.
.. Beyond that, the economic disruption of ending all trade with China would be so huge inside the United States that Mr. Trump’s aides declined on Sunday to discuss the implications.
.. “We are not looking to the total annihilation of a country, namely North Korea,” he said. “But as I said, we have many options to do so.”
.. The North has shown no interest in engaging with the United States unless the Americans end their military presence in the South.
.. the North Korean leader has tried to portray his nuclear program as unstoppable and nonnegotiable
.. “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,” he said. “South Korea is finding, as I have told them, that their talk of appeasement with North Korea will not work, they only understand one thing!”
.. Mr. Trump’s undisguised swipe at the South for “appeasement” was certain to exacerbate fears that the United States might put it in danger. And it came only a day after Mr. Trump threatened a new rift in relations with suggestions that the United States might withdraw from a trade deal with South Korea — one that was intended to bolster the alliance.
.. The test’s timing was a major embarrassment for President Xi Jinping of China, who on Sunday was hosting a summit meeting of the so-called BRICS countries — Brazil, Russia, India, China and South Africa.
.. the test seemed intended to jolt Mr. Xi and convince him that he needed to persuade the United States to talk to North Korea.
.. The timing of the test on Sunday was almost certainly no coincidence: It came during the American Labor Day weekend, and the anniversary of the founding of the North Korean government is next Saturday.
In the coming days, the government is expected to organize huge rallies to celebrate the bomb test and Mr. Kim’s leadership.
.. “Pyongyang has a playbook of strategic provocations, throws off its adversaries through graduated escalation, and seeks maximum political impact by conducting weapons tests on major holidays,”
.. experts have said that the North may have tested a “boosted” atomic bomb that used tritium,