Hydrogen blast over ocean 'would force US to respond'
Would exploding a hydrogen bomb over the Pacific, as North Korea has threatened, push the current war of words between the US and North Korea closer to actual war?
As with much that has transpired lately in the US-North Korea nuclear crisis, no one can be sure where this would lead or whether the North will even carry out its threat. It does, however, raise many questions, including: How would the North undertake such a nuclear test, what risks might it pose to Japan, and how would the US respond?
After Kim Jong-un said Donald Trump would "pay dearly" for threatening to "totally destroy" North Korea, Kim's foreign minister told reporters his country's response to Trump "could be the most powerful detonation of a H-bomb in the Pacific."
All six of North Korea's nuclear tests thus far, dating to 2006, have been conducted in underground tunnels. Experts say the most likely way the North would conduct an atmospheric test over the Pacific is to launch a long-range missile - probably overflying Japan - and have its nuclear warhead detonate in the skies over a remote part of the Pacific.
"I strongly suspect they have the capability to do this," said James Acton, a nuclear expert at the Carnegie Endowment for International Peace. He said that the North likely would do a couple of trial runs with unarmed missiles in coming months before performing the test with an actual H-bomb aboard.
Such a test with a live warhead would tell North Korea's engineers whether their bomb design can survive the rigours of flight and re-entry into the Earth's atmosphere, says Michael Elleman, a missile defence expert at the International Institute for Strategic Studies.
Susan Thornton, the acting secretary of state for East Asia and the Pacific, said yesterday a North Korean H-bomb test in the Pacific would be "outrageous." She said it would draw a "concerted and determined international response" but declined to be specific.
North Korea says it needs nuclear weapons to deter a US invasion, but Thornton contended that the North ultimately seeks to take over US-allied South Korea. She said Kim's aim in developing nuclear weapons is "to fulfil a long-term desire on the part of the North Korean regime to reunify the Korean Peninsula under the Kim family regime and proliferate these weapons and blackmail other countries. This is an intolerable prospect."
Elleman said the missile of choice in a North Korean atmospheric H-bomb test likely would be its longest-range ballistic missile, known as the Hwasong-14, which apparently has the capability of reaching the US mainland, or the intermediate-range Hwasong-12. The Hwasong-14 was flight tested for the first time only two months ago.
"Kim Jong-un would have to accept considerable risk of failure - or worse, a missile carrying a nuclear warhead could crash into Japan - if he elects to use the Hwasong-12 or -14," Elleman said. "The Hwasong-12 has been flight tested just six times, three of which ended in failure."
How might the US respond, given its treaty commitment to defend Japan? Acton argues for negotiating a deal that would preclude such an escalation. He suggests a deal in which the North would agree to halt missile flights over Japan or South Korea and the US would agree to stop its strategic bomber training flights within a certain distance of the Korean border.
Hans Kristensen, a nuclear expert at the Federation of American Scientists, says he thinks the North Korean threat is likely bluster, but if it happened "there's a real possibility the US would take military action in response".