Kim Jong-un finally emerged back onto the world stage this week after a 20-day absence, which led to much speculation about his health and wellbeing.

Smoking and walking briskly, the vision of Mr Kim opening a fertiliser factory outside Pyongyang released by North Korean state media put rumours that he was gravely ill, or dead, to bed.

But that still wasn't quite enough to solve the mystery surrounding why he had been absent for so long or questions over his health.

Some analysts were quick to point out that this had happened before — Mr Kim has suffered issues and disappeared in the past.

And just like in other times, like when he re-emerged with a cane, there were some clues that might explain his absence.

But whatever the reason, Kim was back and ready to let the world know he was in control.

We'll likely never know what really happened

Mintaro Oba, a former US State Department official who worked on North Korea policy issues, told the ABC it was impossible to know if Kim really had suffered severe health issues as a result of a cardiovascular procedure.

"The blunt truth is that we can speculate all we want about where Kim Jong-un was and why he disappeared, but we simply don't know," he said.

"It could be for health reasons, it could be for tactical reasons, we just don't know with any certainty and probably won't."

But Mr Oba said other experts were looking very closely at the photos published by North Korean media of Mr Kim at a ribbon-cutting ceremony on Saturday and had pointed out a couple of things.

He said in particular, they noted a mark on Mr Kim's arm that may indicate he indeed had some kind of cardiovascular procedure.

Sometimes a surgeon will insert a stent through the artery in a patient's arm.

But South Korea's spy agency said there were no signs Mr Kim had undergone heart surgery, according to South Korean news agency Yonhap.

Some have also commented that Mr Kim used a golf cart to get around, possibly indicating he wasn't 100 per cent healthy either.

"Kim has a past history of health problems, and that seemed to be a key reason for a previous disappearance in 2014 when he re-emerged walking with a cane," Mr Oba said.

"So this is certainly a possibility — and something the regime wouldn't want to publicise."

Australia's leading North Korea expert Leonid Petrov also acknowledged it was still possible Mr Kim had a planned surgery, tests or an intrusive examination and that information was leaked to people who "communicate with defectors in China and then South Korea via mobile phone".

But he suggested the information was then "distorted several times" before it was picked up by other media outlets.

So is everyone sure the photo is legit?

Professor of International Security and Intelligence Studies at ANU John Blaxland has cautioned that the recently released pictures of Mr Kim didn't reveal very much.

"We can't even be sure when these were taken, there is the question of if it's even him as he has a body double but I don't give much credence to that theory," he said.

"There's certainly the question of whether or not this is even a real event."

Professor Blaxland said the real question remained over why he missed his grandfather's anniversary.

"This does suggest rumours about him being unwell were valid and it took him time to recover," he said.

Even defectors may have their own agenda

The speculation about Mr Kim's health was sparked after he missed a key anniversary on April 15, the day of the sun, and the commemoration of the birthday of his grandfather Kim Il-sung.

Those rumours were only fuelled by claims from high-profile North Korean defectors that the country's leader was on his death bed.

Thae Yong-ho, a former North Korean ambassador to Britain who was one of two defectors elected to South Korea's Parliament last month, was forced to apologise over spreading misinformation.

Newly-elected South Korean politician Ji Seong-ho was also forced to apologise after saying he was 99 per cent certain that Mr Kim had died after undergoing cardiovascular surgery.

So how did two high-profile former defectors get it so wrong?

Dr Petrov, a senior lecturer at the International College of Management Sydney, said the probability of being right or wrong on anything about North Korea was 50-50.

But he noted many defectors took chances to boost their profile because there were few other opportunities to do so.

"Thae and Ji have been elected to the Republic of Korea Parliament, but their mode of thinking remains deeply embedded in the North Korean partisan ideology of zero-sum game," he said.

"Out of fear of being suspected to be sympathetic towards anything North Korean, they would shoot and run rather than try to present a balanced view or a doubt in public."

Mr Oba also said people who escaped from North Korea have an incredibly unique and valuable perspective on the regime.

But he acknowledged, like others who comment on North Korea, they have their own agenda, biases, and sources of information.

"Their voices are legitimate and have to be heard, but that doesn't free us from the obligation to independently weigh and verify their claims in context," he said.

It's why New York-based political analyst and Asian affairs specialist Sean King suggested that speculating about the North Korean leader was futile.

"If we have learned anything from the last few weeks, it's that it's not worth speculating on Kim Jong-un's disappearances and reappearances," Mr King said.

"Gaming out hypothetical succession scenarios makes sense, as it helps us better understand the regime's ultranationalist, cultish nature.

"But trying to figure out where Kim is, or why he may have been there, has proven a fool's errand. North Korea denies its own people their most basic rights, so why would it ever tell us anything?"

Was there a strategy behind Kim's disappearance?

Mr Oba said he didn't think Mr Kim disappeared to flush out a leaker because this "whole controversy didn't originate from a leak".

"But rather from the fact that Kim Jong-un's public appearances are normally fairly frequent and carefully choreographed and presented in North Korean state media we monitor very closely," he said.

"[Then] he was suddenly absent for a while without explanation."

But Professor Blaxland pointed out that a lack of clear succession would have proven uncomfortable for the elite and that it would be fair to assume Mr Kim would have exploited the opportunity to expose others around him — to not only boost his own standing but potentially flush out any possible overthrowers.

Instability and the possibility of Mr Kim being seen as anything less than a demigod and unwell, would have caused enormous discomfort to the army, elite and party.

"His grip on power remains strong," Professor Blaxland said.

"I suspect there would have been a collective sigh of relief when he returned [to public life]."

Professor Blaxland said Mr Kim would now be looking at consolidating that grip on power.

And while the North Korean elite may have felt discomfort over any future without their current leader, Professor Blaxland said Mr Kim would have been revelling in the attention he was receiving, including from the leader of the United States.

Kim's showing he's still the one in charge

If one thing was clear it was Mr Kim was back in the picture — and ready to make a point.

Dr Petrov said it was hardly a coincidence that Mr Kim reappeared following days of speculation over his health and shots were soon fired from North Korea in the heavily-fortified demilitarised zone (DMZ).

He also said it looked like Mr Kim was trying to demonstrate who was calling the shots in North Korea and on the Korean Peninsula.

"I don't have any other explanation to this senseless use of live fire at the source of cash and concessions," he said.

"Kim clearly stated that he is in power, and he does not want anything from South Korea because he has more powerful friends in Washington DC, Beijing and Moscow."

The shots from the north hit a guard post in the central border town of Cheorwon, and fire was returned from the south.

Incidents in the area which divides the two countries are rare, however both South Korea and the US insist the shots were not likely to have been intentional.