An expert on North Korean affairs says the country's latest nuclear test is intended to show it is making advances in nuclear technology as well as missile development.
NHK spoke with Nanzan University Professor Shunji Hiraiwa by telephone.
Hiraiwa said the North Korean regime has been observing the reaction of the US government to its threatened missile launch near the US Pacific territory of Guam, and the firing of a missile over Japan. He said Pyongyang may have judged from this reaction that it was OK to go ahead with the nuclear test.
He said the international community was somewhat skeptical of the North's ability to miniaturize a nuclear warhead, while agreeing its missile technology had reached a certain capability.
Hiraiwa said a missile could not be a threat to the United States unless it was armed with a nuclear weapon. He said the nuclear test was meant to show that Pyongyang is also advancing its nuclear bomb technology.
Hiraiwa said the test was also a protest against the UN Security Council's presidential statement against North Korea, and a warning to Japan. He said the North may accelerate testing around its National Foundation Day on September 9th.
"Pyongyang pursuing a bargaining chip with the US"
Another expert on North Korea says the latest nuclear test is meant to be a bargaining chip.
Professor Hajime Izumi of Tokyo International University said all of the North's provocations are meant to drag the United States to the negotiating table without conditions.
He said Pyongyang's message is as follows: "We are obtaining the capabilities to attack you, and if you want us to stop, negotiate."
Izumi said the North claims it tested a hydrogen bomb, which is far more powerful than a conventional nuclear bomb, while the international community was skeptical of its ability to mount a nuclear warhead on a missile.
He said this was meant to show that North Korea could inflict widespread devastation on the United States with a hydrogen bomb.
## "Significant improvement in North Korean technology"
Professor Tatsujiro Suzuki is Director of Nagasaki University's Research Center for Nuclear Weapons Abolition. He spoke to NHK over the phone.
He said the intensity of the tremor from the test suggests the size of the explosion exceeded that of the atomic bomb dropped on Hiroshima at the end of World War Two.
He said it's difficult to miniaturize nuclear weapons, but with the past 6 tests, North Korea's technology has improved significantly. He said it's just a matter of time before the North is able to mount a small nuclear warhead on an intercontinental ballistic missile.
North Korea has said that it's developing a 2-stage nuclear bomb.
Suzuki said the North may have tested a fission bomb, boosted by a nuclear fusion reaction, using substances like heavy hydrogen and tritium.
Suzuki explained that nuclear fission in the first stage causes a fusion reaction in the second stage. He said this type of bomb is more powerful despite its size, and easier to mount on a missile.