Two days before his birthday, North Korean supreme leader Kim Jong Un flexed his military muscle once more, this time by claiming to have successfully tested a hydrogen bomb many times more powerful than previous atomic detonations by the reclusive nation.
The announcement on Wednesday was a particular affront to the country's immediate neighbours - South Korea and China - on the part of the young dictator, who is believed to be in his early 30s.
Expert observers immediately expressed scepticism over whether the new test really did involve a fully developed nuclear fusion device, in which atoms are joined, as opposed to the nuclear fission - or atom-splitting - tests carried out on three earlier occasions.
But there is little doubt about Pyongyang's determination to create a military nuclear capacity that will act as a deterrent to all comers. The dictatorship justifies its nuclear arms programme on the basis of an alleged threat from the United States.
Pyongyang tested its first nuclear device 10 years ago, leading to the imposition of economic sanctions by the UN. The tests contravene Security Council resolutions in the view of its neighbours and the US.
Now it appears that South Korea's hopes of ending the spiral of provocation and threat, followed by apparent attempts at rapprochement, have once again been dealt a severe setback.
South Korean President Park Geun Hye made unmistakably clear that Pyongyang would pay a price for this renewed demonstration of aggression.
But many in the region now fear that a tightening of sanctions will merely lead to more threats from Kim.
"The North Koreans should know precisely what will come down on them," says Lars-Andre Richter of the German Friedrich Naumann Foundation's Seoul branch. He sees the latest test as "two steps backwards" for relations between the two Koreas.
As recently as August the two countries agreed on cautious rapprochement, but South Korea may have been too trusting here, Richter believes.
North Korea has repeatedly threatened a new nuclear test.
There have also been warnings from the South Korean military and intelligence services that a testing range in north-eastern Kilju County was being extended and that a new test could be conducted at any time.
In addition, Pyongyang has been busy coordinating its nuclear and missile programmes - observers believe a missile test could take place in the near future.
"I'm not surprised by the test," says Park Hyeong Jung, a researcher at the state-run Korea Institute for National Unification (KINU) in Seoul. "North Korea is not frightened of sanctions," he says.
Park sees the main reason behind the test as improving skills in the area of bomb making, with Kim's need to further stabilize his position as a secondary reason.
Hartmut Koschyk, chairman of the German-Korean parliamentary group, who visited Pyongyang in October, takes a similar view. "Kim has to prove himself with respect to the military complex," he says.
At the time a hardening of Pyongyang's position on its nuclear programme was clear, particularly with respect to the US, Koschyk says.
Nevertheless, there could now be increased pressure on North Korea. Beijing in particular is disappointed that Kim has ignored its warnings on renewed testing.
Following a long frosty period, in October the Chinese leadership sent a politburo member to the military parade marking 70 years since the founding of the Workers' Party of North Korea, suggesting a thaw in relations.
Yu Yingli of the Institute for International Studies in Shanghai now predicts that relations between Beijing and Pyongyang will cool once more.