Any change to the leadership in Pyongyang threatens a struggle for control of one of the world's most dangerous stockpiles of nuclear and chemical weapons.

Despite state media showing the North Korean Supreme Leader reemerge at the opening of a fertiliser factory, questions over his health have lingered, and intelligence agencies from Seoul to Washington are left facing one key question - who is next in line to replace Kim Jong Un?

When Kim Jong Un was handed power after the death of his father, Kim Jong, Il in 2011, experts braced themselves for regime collapse.

The young leader, who had spent part of his youth in Europe, only emerged as the anointed successor barely two years earlier, and few thought he had the authority to hold the Kim dynasty together.

However, the now 36-year-old dictator defied expectations by removing threats to his power, including the brutal killings of his uncle and half brother.

With few close family members left and his own children believed to be far too young, the next in line could be Kim Yo Jong, the Supreme Leader's younger sister.

Kim Yo Jong gained international prominence in 2018 when she was dispatched to attend the Winter Olympics in South Korea and became the first member of the Kim regime to visit the country since the Korean War.

She is believed to have important roles in political departments in Pyongyang and is seen to be a top advisor to her brother, including during his flurries of brinkmanship and diplomacy with Donald Trump.

Based on the regime's priorities and the regime's propaganda and what Kim Jong Un himself has done in the past few years, is that his sister is very close to him.

Kim Yo Jong, who is in her early 30s, is always by her brother's side, is obviously a trusted confidant.

She would be near the top, if not at the top of that list, of my list of who might succeed.

I think we have to understand that this is all at Kim's whim.

He has been purging, demoting, shuffling leaders left and right, hundreds of officials since he came to power.

And that's a way of keeping everybody on their toes.

And so if you're in that kind of environment, then you're going to want to make sure that you're in the leader's good graces.

US officials see Kim Yo Jong as one of the key regime insiders, with one analyst telling me she has been groomed for power and the propaganda game since she was a teenager.

Secretary of State Mike Pompeo, who has travelled to Pyongyang and met Chairman Kim himself several times, including when he was CIA chief, made a point of saying that he had also met Chairman Kim's sister on past trips, as well as some of the other leaders, as well.

One person I spoke to who is directly in touch with North Korean and Chinese officials told me that, even if Kim's sister were to take over as figurehead, the party would try to project leadership in a style akin to that of China before Xi Jinping took the reins, portraying something more akin to collective leadership.

Analysts I spoke to said the Trump administration has also taken its eye off the ball, as the prospect for talks with North Korea that might actually yield fruit have dwindled, and the team they assembled to try and deliver denuclearisation has scattered in different directions.

Managing a transition with such high stakes at a time the US is fighting coronavirus, if that were to be the case, would be extremely demanding.

The speculation over Kim's health and whereabouts has also highlighted just how little insight we have into the North Korean leadership.

There are multiple Ints, which is human intelligence, signals intelligence, Geoint, and that's the satellite imagery, what we see from above, as well as open source, Osint, and also Rumint, which is rumour intelligence, right?

But something like Kim's health or his whereabouts or his status, that's tricky.

The search for Kim Jong Un appears to have come to an end for now, but the episode has served as a stark reminder of the potential for a sudden dramatic change in the leadership in Pyongyang and the dangers of having an unstable nuclear-armed pariah state that shares borders with China and South Korea and has a history of threatening the United States.