When North Korea hinted it had a hydrogen bomb last month – twice – it was largely brushed off as bluster.

At the heart of every decision the regime makes is one overriding concern: the survival of the regime itself, which depends on the glorification of its leader, Kim Jong Un, and the ability to keep at bay the United States and its allies, which Pyongyang considers to be an existential threat.

The North, officially the Democratic People's Republic of Korea, has long claimed it has the right to develop nuclear weapons to defend itself against the U.S., an established nuclear power against whom it has been in a state of war for more than 65 years. But to build a credible nuclear threat, the North must explode new nuclear devices – including miniaturized ones – so its scientists can improve their designs and technology.

The event, strongly hyped in the North Korean media, will be watched closely by North Korean elites and North Korea watchers abroad for signs of whether the young Kim – still in his early 30s – will step out of his father's and grandfather's shadows and assert his own leadership more boldly.

If the international fallout from the test doesn't prove to be too unmanageable, having it under his belt could allow Kim to go into that meeting with bragging rights that neither of his predecessors had, along with a bolstered position among North Korea's powerful military and nuclear weapons bureaucracies.

The Obama administration, meanwhile, has made clear it isn't interested in improving ties with North Korea unless Pyongyang gives up its nuclear weapons program.

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