It was a bitterly cold day in Pyongyang - 28 December 2011.
Snow was falling hard as a long black Lincoln Continental car drove slowly through the streets. On the roof, on a bed of white chrysanthemums, lay the coffin of North Korea鈥檚 Supreme Leader Kim Jong-il.
Vast crowds dressed in black lined the streets. They had to be held back by soldiers as they wept uncontrollably, beating their chests and calling out 鈥渇ather, father鈥.
Beside the car walked the dead dictator鈥檚 son and successor Kim Jong-un. Just 27, he looked overwhelmed. He broke down in tears several times during the ceremony.
Directly behind Kim walked his uncle Chang Song-thaek, considered to be the second most powerful man in North Korea. On the other side walked army Chief of Staff Ri Yong-ho and Defence Minister Kim Yong-chun.
These were the old men who would now wield power in Pyongyang. Or so many thought.
In the 1950s Kim Jong-un鈥檚 grandfather Kim Il-sung created something unique in the communist world - North Korea鈥檚 one-man hereditary leadership.
For nearly two decades Kim groomed his eldest son Kim Jong-il to succeed him. Wherever he went, the crown prince was at his side. In 1994, when the old man died, Kim Jong-il immediately took charge. But when he then died suddenly in 2011 his own son had barely begun his apprenticeship to become North Korea鈥檚 third Supreme Leader. Many experts now predicted the collapse of one-man-rule. They were soon to be proved wrong.
Within months Chief of Staff Ri Yong-ho and Defence Minister Kim Yong-chun had both been dismissed. Ri鈥檚 whereabouts remain a mystery to this day.
Then in December 2013 Kim Jong-un made his most dramatic move. His own uncle, Chang Song-thaek, was hauled from a party meeting, accused of treason and executed, with some unconfirmed reports even suggesting an anti-aircraft gun had been used.
Between 2012 and 2016 Kim carried out the biggest purge seen in North Korea since the days of his grandfather. South Korea鈥檚 Institute for National Security Strategy has reported the execution of 140 senior military officers and government officials. Another 200 have been removed or imprisoned.
Kim has removed anybody who stood in his way, replacing them with a younger cadre loyal to him. They are led by his own sister Kim Yo-jong, who in 2017 was appointed to the Politburo at the age of 30.
Today no-one is in doubt who pulls the levers of power in Pyongyang. Kim Jong-un is the Supreme Leader.
It鈥檚 a warm April afternoon in 2018 and Kim Jong-un is sitting on a wooden bridge in a forest glade in the middle of the demilitarised zone (DMZ) that divides North and South Korea.
Six years have passed since that bitterly cold day in Pyongyang.
Kim is sipping tea and listening intently to South Korea鈥檚 President Moon Jae-in. The meeting is being broadcast live around the world. No-one watching can hear a word they鈥檙e saying.
For half an hour many around the world watch transfixed by this mute conversation, trying to read every gesture.
Just months before Kim had been test-firing missiles over Japan and threatening to rain fire on Seoul and the US.
Now he is sitting, smiling, deep in conversation with his sworn enemy.
How does one reconcile this image with that of a man who was prepared to have his own uncle killed?
There are so many questions. What does Kim want? Is this a bluff, a charm offensive? Or is Kim Jong-un now determined to take a different path from the one set out by his grandfather Kim Il-sung, and handed on to him by his father Kim Jong-il?
The year is 1992 and at a villa in Pyongyang a very special birthday party is being held for an eight-year-old boy. Among the presents one stands out.
It is a general鈥檚 uniform. Not a toy, but the real thing - a miniature but otherwise totally authentic uniform of a general of the Korean People鈥檚 Army.
Other, much older generals arrive at the party and bow before the eight-year-old boy. His name is Kim Jong-un.
The story of how this eight-year-old became 鈥淕eneral Kim鈥 was recounted to the Washington Post in an interview with Kim鈥檚 aunt in 2016. Nearly two decades earlier Ko Yong-suk and her husband had defected to the West. They now live in quiet seclusion outside New York.
In the interview Ko said that birthday party convinced her Kim Jong-un was being anointed as successor to his father Kim Jong-il.
鈥淚t was impossible for him to grow up as a normal person when the people around him were treating him like that,鈥 Ko said.
A few years later Ko Yong-suk was assigned to accompany Kim Jong-un when his father sent him to private school in Switzerland.
She described the teenage Kim as hot-tempered and arrogant.
鈥淗e wasn鈥檛 a troublemaker, but he was short-tempered and had a lack of tolerance. When his mother tried to tell him off for playing too much and not studying enough, he wouldn鈥檛 talk back, but he would protest in other ways like going on hunger strike.鈥
Tiny snippets like these are virtually all we know of Kim Jong-un鈥檚 childhood. It鈥檚 not much on which to build a picture of who he is and why he was chosen to succeed his father over his older brother Kim Jong-chol, and half-brother Kim Jong-nam.
The first to predict Kim Jong-un鈥檚 rise to power may have been a Japanese sushi chef who goes by the alias of Kenji Fujimoto.
During the 1990s Fujimoto became an unlikely member of the Kims鈥 inner circle. He made Japanese food for Kim Jong-il, and claims he was the young Kim Jong-un鈥檚 鈥減laymate鈥.
In 2001 Fujimoto returned to Japan and published his inside story. In it he described his first encounter with Kim Jong-un, and his older brother Kim Jong-chol.
鈥淭he first time I met the two young princes, they were both wearing military uniforms. They shook hands with each of the staff. But when it came to shaking my hand, Prince Kim Jong-un gave me an icy glare. It was like he wanted to say, 鈥榃e hate Japanese like you鈥. I will never forget his sharp stare. He was seven years old.鈥
In a second book in 2003 Fujimoto wrote:
鈥淜im Jong-chol is regarded as the most likely successor. But I doubt that very much. Kim Jong-il used to say, 鈥楯ong-chol is no good, he is like a girl鈥. His favorite is his youngest son, the second prince. Jong-un is very much like his father. He is even built like his father. But his existence has not been revealed to the public.鈥
It was a remarkable prediction. At the time Kim Jong-un had not been introduced to the North Korean people, let alone the outside world. Most of his childhood was still a complete secret.
When Choi Min-jun was 14, he was selected to join the most elite unit in the North Korean military - the Supreme Guard Command. Today he is a defector living in South Korea under an assumed name.
We recently got a glimpse of the secretive unit that protects North Korea鈥檚 royal dynasty. As Kim Jong-un arrived for the summit with South Korean President Moon Jae-in in April a group of tall besuited bodyguards were filmed running alongside his Mercedes limousine. These men were from the inner rank of the Supreme Guard Command, the most elite of the elite.
Choi Min-jun had no chance of entering that inner circle. He was not tall enough. But more importantly he had the wrong family background.
鈥淚 was not born into the highest rank of society,鈥 Choi tells me, 鈥渟o, I could not serve in the Supreme Leader鈥檚 personal bodyguard. Instead I was assigned to his combat unit.鈥
For all its protestations of being a socialist state, North Korea has an elaborate and rigid caste system that classifies every person from birth. It is called Songbun. The website NKNews describes Songbun thus:
鈥淚t divides the population into groups, according to the actions and status of their paternal ancestor during the Japanese colonial period and the Korean War. Songbun determines whether one is allowed to live in the capital, the workplace one is allocated and what kind of education one can receive.鈥
Crucially Songbun status cannot be changed. If your grandfather fought against the Japanese during the occupation of Korea you are considered 鈥渓oyal鈥. If he worked for the Japanese colonial rulers you are an 鈥渆nemy鈥 and always will be.
Choi鈥檚 own family were peasant farmers - they had not served the Japanese, but nor had they opposed them. And so Choi was sent to a combat unit. At the time his 鈥渟tatus鈥 did nothing to blunt his loyalty.
鈥淚n North Korea, you are brainwashed from a young age,鈥 he says. 鈥淚 was taught that the Kim family are gods. And I believed it.
鈥淲hen Kim Il-sung made his new year address and said this year we must mine more coal, I said: 鈥業 will go to the mines!鈥 That's how naive and loyal to the Kim family I was.鈥
Choi rapidly discovered the Supreme Guard Command was not there to protect the Kims from foreign enemies, but from their own people.
鈥淔or the Kim family, everyone is a potential enemy,鈥 he tells me. 鈥淭he North Korean military, the General Staff Department, the Ministry of the People鈥檚 Armed Forces as well as the entire North Korean people, they are all potential enemies.鈥
Choi was trained to trust no-one, not even his own parents.
As the Kim family鈥檚 paranoia grew so did the size of this personal security force.
鈥淲hen the Kim family saw the collapse of the Eastern bloc and the fall of the Soviet Union they were shocked,鈥 he says. 鈥淭hey drastically increased the size of the Supreme Guard Command. Now it numbers almost 120,000 soldiers.鈥
Like a medieval royal house, the Kim regime is jealous of its power and sees enemies all around.
And like many royal families through the ages, it sometimes kills to protect its position.
Choi鈥檚 own family were peasant farmers - they had not served the Japanese, but nor had they opposed them. And so Choi was sent to a combat unit. At the time his 鈥渟tatus鈥 did nothing to blunt his loyalty.
鈥淚n North Korea, you are brainwashed from a young age,鈥 he says. 鈥淚 was taught that the Kim family are gods. And I believed it.
鈥淲hen Kim Il-sung made his new year address and said this year we must mine more coal, I said: 鈥業 will go to the mines!鈥 That's how naive and loyal to the Kim family I was.鈥
Choi rapidly discovered the Supreme Guard Command was not there to protect the Kims from foreign enemies, but from their own people.
鈥淔or the Kim family, everyone is a potential enemy,鈥 he tells me. 鈥淭he North Korean military, the General Staff Department, the Ministry of the People鈥檚 Armed Forces as well as the entire North Korean people, they are all potential enemies.鈥
Choi was trained to trust no-one, not even his own parents.
As the Kim family鈥檚 paranoia grew so did the size of this personal security force.
鈥淲hen the Kim family saw the collapse of the eastern bloc and the fall of the Soviet Union they were shocked,鈥 he says. 鈥淭hey drastically increased the size of the Supreme Guard Command. Now it numbers almost 120,000 soldiers.鈥
Like a medieval royal house, the Kim regime is jealous of its power and sees enemies all around.
And like many royal families through the ages, it must sometimes kill to protect its position.
On 12 February 2017, a group of friends gathered in a restaurant in the Malaysian capital Kuala Lumpur. They had come to celebrate the 25th birthday of an Indonesian woman, Siti Aisyah. Video from one of her friends' phones shows her smiling and blowing out a candle and singing.
According to Aisyah鈥檚 account of the night, she told her friends she had exciting news. She鈥檇 landed a job on a TV reality show. Finally, she could escape the sleazy Kuala Lumpur bathhouse where she worked. Her friends toasted her: 鈥淵ou are going to be a star!鈥
The next morning at Kuala Lumpur airport Siti Aisyah spotted her target, a rotund balding man in blue T-shirt and sports jacket. As he approached the check-in she ran up to him and splashed a liquid in his face.
鈥淲hat are you doing?鈥 he spluttered in broken English.
鈥淪orry,鈥 she said as she ran away.
According to Aisyah鈥檚 version of what happened - which has not stopped her being charged with murder by the Malaysian authorities - it was all just a prank for the TV show.
Sitting in a caf茅 a few metres away were a group of alleged North Korean agents. Apparently satisfied their mission had been completed, CCTV footage shows them walking to the departure gate and boarding a flight to Dubai.
The rotund man was now starting to feel unwell. His face was itchy and he was finding it harder to breathe. Within minutes he was slumped on a chair unconscious. Airport staff called an ambulance. As it sped towards Kuala Lumpur his lungs filled with fluid and he drowned.
The man鈥檚 passport said he was a North Korean diplomat called Kim Chul. In fact, the dead man was Kim Jong-nam, the older half-brother of Kim Jong-un.
Kim Jong-nam had been poisoned with a powerful nerve agent - VX. Inhaling a drop the size of a grain of sand is enough to kill.
Kim鈥檚 was a brazen killing and - despite North Korea denying any involvement - all the evidence seemed to point towards his younger half-brother in Pyongyang. But what was the motive?
Their father Kim Jong-il had a complicated love life. He had two official wives, and at least three mistresses, with whom he fathered five children. Kim Jong-nam was the child of his first mistress Song Hye-rim. Kim Jong-un was the younger son of his second mistress Ko Yong-hui, a former actress born in Japan. The old dictator kept his mistresses and their children secret. They lived in secluded villas, isolated from each other. Though they shared a father, Kim Jong-nam and Kim Jong-un never met.
As the oldest son, Kim Jong-nam was long considered Kim Jong-il鈥檚 most likely successor. But in 2001 he was arrested as he attempted to enter Japan on a fake passport. He had planned to visit Tokyo鈥檚 Disneyland.
The crown prince of North Korea was filmed being marched to a plane and expelled. For his father in Pyongyang it was a humiliation he could never forgive. Kim Jong-nam was removed from the succession and sent into exile in China. Or so the story goes.
But that is not the whole story.
Kim Jong-nam had been poisoned with a powerful nerve agent, VX. Inhaling a drop the size of a grain of sand is enough to kill.
Kim鈥檚 was a brazen killing and all the evidence pointed towards his younger half-brother in Pyongyang. Why?
Their father Kim Jong-il had a complicated love life. He had two official wives, and at least three mistresses, with whom he fathered five children. Kim Jong-nam was the child of his first mistress Song Hye-rim. Kim Jong-un was the younger son of his second mistress Ko Yong-hui, a former actress born in Japan. The old dictator kept his mistresses and their children secret. They lived in secluded villas, isolated from each other. Though they shared a father, Kim Jong-nam and Kim Jong-un never met.
As the oldest son Kim Jong-nam was long considered Kim Jong-il鈥檚 most likely successor. But in 2001 he was arrested as he attempted to enter Japan on a fake passport. He planned to visit Tokyo鈥檚 Disneyland.
The crown prince of North Korea was filmed being marched to a plane and expelled. For his father in Pyongyang it was a humiliation he could never forgive. Kim Jong-nam was removed from the succession and sent in to exile in China. Or so the story goes.
But that is not the whole story.
The next in line should have been Kim Jong-il鈥檚 middle son Kim Jong-chol. But it appears he was never seriously considered. Instead he chose his youngest son Kim-Jong-un.
According to Martin: 鈥淗e was chosen by his father because he was the meanest and nastiest of the sons.鈥
In other words, he had the best chance of surviving a brutal succession struggle and keeping the family business alive.
He has certainly shown his ruthlessness. According to Gomi, once Kim Jong-il was dead, and Kim Jong-un took over, his half-brother began to get nervous.
鈥淎fter Kim Jong-il died Kim Jong-nam suddenly felt unsafe. The last time we communicated was in January 2012. At that time, Kim Jong-nam said to me, 鈥楳y brother and the Kim dynasty will do something dangerous to me鈥.鈥
Martin believes Kim Jong-un had his own brother killed. He has his own theory why.
鈥淚t fits with the killing of [his uncle] Chang Song-thaek,鈥 he says. 鈥淐hang was charged with planning a coup d鈥櫭﹖at. We [the Western media] ignored that. Then Kim Jong-un went after the brother. We have these reports that Chang went to China and said, 鈥楲et鈥檚 get rid of Kim Jong-un and put Kim Jong-nam in鈥. Kim thinks: 鈥楳y uncle and my older brother are plotting against me and are in cahoots with the Chinese.鈥 It makes a certain amount of sense.鈥
That is just a theory, but his further conclusion seems irrefutable.
鈥淭here are now no further threats to his rule. His internal challengers are gone.鈥
Kim Jong-un now rules supreme. But what does he want for his small impoverished country?
In the summer of 1998, Kim Jong-un was back in North Korea, on holiday from school in Switzerland. He鈥檇 been out to the family鈥檚 huge summer compound beside the sea near Wonsan.
Now he was on a train heading back to the capital, Pyongyang. Sitting with him looking out at the villages and rice paddies was Japanese chef Kenji Fujimoto.
In his 2003 book Fujimoto says Kim Jong-un told him: 鈥淔ujimoto, our country is behind in industrial technologies even compared with other Asian countries. We still have power cuts.鈥
He says Kim then compared North Korea鈥檚 situation to China.
鈥淚 heard that China has been successful in many ways. We have a population of 23 million people. China has a population of over a billion. How do they manage to supply power? It must be difficult to produce enough food for a billion people. We need to follow the example set by them.鈥
If Fujimoto鈥檚 story is true then the young Kim Jong-un was expressing sacrilegious thoughts.
Since 1955 the guiding ideology of North Korea has been Juche. The word is often translated as 鈥渟elf-reliance鈥. It is Kim Il-sung鈥檚 鈥済reat contribution鈥 to Marxist-Leninist thought. There is a vast memorial dedicated to Juche on the south bank of the Daedong River in Pyongyang. Making fun of it is not advised.
But Juche is a myth. North Korea is not self-reliant and never has been. For its first 40 years the country was almost entirely dependent on Moscow for economic support. When the Soviet Union collapsed, North Korea鈥檚 state-run economy fell apart and its people starved.
In the midst of the famine North Korea鈥檚 people began to trade. Out of the chaos and collapse of the 1990s a new economy emerged. Unregulated and officially unrecognised, it nevertheless keeps North Korea鈥檚 people alive.
The extent of this 鈥渂lack鈥 economy became clear to me while interviewing a young defector in Seoul in 2012.
South Korean President Park Geun-hye had just ordered the closure of the Kaesong Industrial Zone - just across the DMZ in North Korea.
鈥淲hen I heard the news, I called my father and told him to go to China and buy Choco Pies,鈥 the young defector told me.
This left me confused.
鈥淪orry,鈥 I said, 鈥渨here is your father?鈥
鈥淚n North Korea,鈥 he said.
鈥淗ow do you call him?鈥 I asked.
His father, it turns out, has a Chinese sim card for his mobile phone. This is illegal and dangerous, but also common. Once a week he travels to the Chinese border, connects to a Chinese mobile network, and his son can call him.
鈥淎nd what about the Choco Pies?鈥 I asked.
South Korean companies operating in the Kaesong Industrial zone had been paying their North Korean workers, in part, with South Korean products. One of the most popular was Choco Pies.
They were so popular they had become a kind of black-market currency in the North. Now that the Kaesong zone had shut, the black-market price for Choco Pies would sky rocket. So, he told his father to go to China and bring back as many boxes as he could carry, the profits would be good.
At a church on the outskirts of Seoul I met a very different defector. He was short with wide muscular shoulders, missing teeth, and a heavy accent my South Korean translator struggled to understand.
鈥淚 was a smuggler,鈥 he said.
He described how his gang bribed North Korea border guards to leave a section of the border unguarded at night. They would then cross in to China carrying scrap metal and valuable minerals.
鈥淲hat did you smuggle back?" I asked
鈥淎ll sort of things, food, clothes, DVDs, drugs, pornography,鈥 he said. 鈥淒rugs and pornography are dangerous.鈥
鈥淲hat鈥檚 the most dangerous thing to smuggle out of North Korea?鈥 I asked
鈥淚f you take scrap metal from a Kim statue, that can get you shot,鈥 he said.
The goods imported and smuggled from China are traded at large markets that have sprouted up in every city and town.
This informal economy is working. A new class of monied entrepreneurs is reported to be buying property in Pyongyang. North Korea鈥檚 economy is growing. But there has been no ideological shift, nothing to indicate a fundamental change from the top.
Then on 20 April this year, at a plenary session of the Worker鈥檚 Party of Korea, Kim Jong-un made a speech entitled:
鈥淭he further acceleration of socialist construction as required by a fresh high stage of the developing revolution.鈥
In it Kim declared a freeze on all further testing of nuclear weapons and long-range missiles and a 鈥渘ew strategic line鈥 that would focus on building North Korea鈥檚 economy. This speech has been taken by some observers as a signal that Kim Jong-un is ready to fulfil that promise he made on the train - to follow China鈥檚 example.
One is John Delury from Yonsei University in Seoul.
鈥淭he new strategy is economics first - 100% on the economy,鈥 he says. 鈥淜im is saying, 鈥業'm really going to improve the economy. You're not going to have to tighten your belts again.鈥
鈥淔or the last five or six years it has been modest improvement but nothing breakthrough. Instead he's obviously been focused on the nuclear programme. And so we're now seeing a pivot.鈥
Others, like Bradley K Martin, are far less certain.
鈥淚s he seriously thinking he can transform this country? I don鈥檛 know. It doesn鈥檛 fit with what we know about him. He鈥檚 had years to do so if he wanted to. He has done showmanship like his father and his grandfather. 鈥楲et鈥檚 build monuments.鈥 Each has done the same thing.
鈥淚 have seen no evidence the economy has really been reformed except for tacitly admitting that there is another economy 鈥 which it had to. Everyone would have died if it hadn鈥檛 been for the 鈥榦ther economy鈥.鈥
If Kim Jong-un is now intent on developing his country he needs sanctions lifted. He needs trade and massive investment. To get that, the US and its allies will demand he give up his 鈥渢reasured sword鈥, his nuclear weapons. Is that what he now intends?
At a church on the outskirts of Seoul I met a very different defector. He was short with wide muscular shoulders, missing teeth, and a heavy accent my South Korean translator struggled to understand.
鈥淚 was a smuggler,鈥 he said.
He described how his gang bribed North Korea border guards to leave a section of the border unguarded at night. They would then cross in to China carrying scrap metal and valuable minerals.
鈥淲hat did you smuggle back? I asked
鈥淎ll sort of things, food, clothes, DVDs, drugs, pornography,鈥 he said. 鈥淒rugs and pornography are dangerous.鈥
鈥淲hat鈥檚 the most dangerous thing to smuggle out of North Korea?鈥 I asked
鈥淚f you take scrap metal from a Kim statue, that can get you shot,鈥 he said
The goods imported and smuggled from China are traded at large markets that have sprouted up in every city and town.
This informal economy is working. A new class of monied entrepreneurs is reported to be buying property in Pyongyang. North Korea鈥檚 economy is growing. But there has been no ideological shift, nothing to indicate a fundamental change from the top.
Then on 20 April this year, at a plenary session of the Worker鈥檚 Party of Korea, Kim Jong-un made a speech entitled:
鈥淭he further acceleration of socialist construction as required by a fresh high stage of the developing revolution.鈥
In it Kim declared a freeze on all further testing of nuclear weapons and long-range missiles and a 鈥渘ew strategic line鈥 that would focus on building North Korea鈥檚 economy. This speech has been taken by some observers as a signal that Kim Jong-un is ready to fulfil that promise he made on the train - to follow China鈥檚 example.
One is John Delury from Yonsei University in Seoul.
鈥淭he new strategy is economics first - 100% on the economy,鈥 he says. 鈥淜im is saying, 鈥業'm really going to improve the economy. You're not going to have to tighten your belts again.鈥
鈥淔or the last five or six years it has been modest improvement but nothing breakthrough. Instead he's obviously been focused on the nuclear program. And so we're now seeing a pivot.鈥
Others, like Bradley K Martin, are far less certain.
鈥淚s he seriously thinking he can transform this country? I don鈥檛 know. It doesn鈥檛 fit with what we know about him. He鈥檚 had years to do so if he wanted to. He has done showmanship like his father and his grandfather. 鈥楲et鈥檚 build monuments.鈥 Each has done the same thing.
鈥淚 have seen no evidence the economy has really been reformed except for tacitly admitting that there is another economy 鈥 which it had to. Everyone would have died if it hadn鈥檛 been for the 鈥榦ther economy鈥.鈥
If Kim Jong-un is now intent on developing his country he needs sanctions lifted. He needs trade and massive investment. To get that America and its allies will demand he give up his 鈥渢reasured sword鈥, his nuclear weapons. Is that what he now intends?
Early on the morning of 4 July 2017 a US spy satellite flying high above North Korea spotted activity at an airfield in North Pyongan Province. A huge 16-wheel 鈥渢ransporter erector launcher鈥 (TEL) drove on to the airfield. It had a large missile on its back.
Over the next hour US intelligence officers watched as the missile was erected and fuelled for launch. During the operation they could clearly see a man strolling around the missile, smoking a cigarette.
This story was told by Ankit Panda, the editor of The Diplomat magazine, who says it was leaked to him by an intelligence source. The man with the cigarette, so close to a rocket full of inflammable fuel, could only have been Kim Jong-un.
Shortly after dawn the missile鈥檚 main engine fired and it roared skywards, flying nearly 3000km into space before splashing down in the Sea of Japan. Kim Jong-un was jubilant. Photos released later showed him smiling and hugging senior military officers. And there in his hand was the tell-tale cigarette.
Pyongyang claimed the rocket was a new intercontinental ballistic missile capable of hitting the US and that the launch was a 4 July gift to President Donald Trump.
North Korea has pursued its nuclear weapons programme doggedly, at great economic cost and in the face of intense international pressure to desist.
After coming to power in 2011 Kim Jong-un dramatically accelerated the North鈥檚 nuclear and missile programme, conducting many more ballistic missile tests over a shorter period of time than his father had.
On 29 November last year it culminated with the launch of an enormous new missile, the Hwasong-15. North Korea鈥檚 state news agency KCNA said the new missile was capable of carrying a 鈥渟uperheavyweight warhead鈥 and striking the whole of the mainland US.
The KCNA report said Kim Jong-un 鈥渄eclared with pride that now we have finally realised the great historic cause of completing the state nuclear force, the cause of building a rocket power鈥.
Many outside experts agreed - Kim could now hit the US.
It was just over a month between that declaration and Kim Jong-un鈥檚 2018 New Year message in which he offered to send a delegation to the Winter Olympics in South Korea.
That message was read by many in the outside world as a dramatic switch by Kim to engagement.
But some very important questions remain: Why was Kim so determined to develop long range weapons capable of hitting the US? What is his nuclear missile arsenal for?
How you answer these questions will determine whether you believe Kim wants 鈥減eaceful coexistence鈥 with South Korea, and is prepared to negotiate an end to his nuclear programme, or not.
At his recent summit with President Moon, Kim Jong-un called for the 鈥渃omplete denuclearisation of the Korean peninsula鈥, and promised to halt all further tests and dismantle his nuclear testing facilities. But according to nuclear weapons expert Duyeon Kim, of the Korean Peninsula Future Forum, that does not mean Kim Jong-un is ready to unilaterally disarm - far from it.
鈥淗e actually declared that it [North Korea] is a nuclear power,鈥 she says. 鈥淭hat's what advanced responsible nuclear powers say. They don't have to test any more after about six nuclear tests. So Kim Jong-un is gearing up his persona, walking into these summits to be perceived as the leader of a normal powerful country on equal footing with the US.鈥
There is a widely held view that North Korea鈥檚 nuclear weapons are defensive - that the Kim dynasty watched the fall of Saddam Hussein and then Colonel Gaddafi and decided that nukes are the only sure way of preventing US-led 鈥渞egime change鈥.
Critics of that view say neither Kim Jong-un, nor his father, ever needed ICBMs to protect themselves. One is Prof Brian Myers of Dongseo University in Busan. In a recent speech to the Royal Asiatic Society, he said: 鈥淥ur inability to stop this regime from acquiring nuclear weapons shows they were never vital to its security. If a North Korea without them were as vulnerable as Libya without them, it would have been bombed by 1998 at the latest.鈥
The reason that didn鈥檛 happen is South Korea鈥檚 extreme vulnerability to counter-attack. The capital, Seoul, lies only 50km from the DMZ, well within North Korean artillery range.
So if you were to accept Kim鈥檚 nuclear missiles aren鈥檛 needed for defence, what are they for? The answer according to Duyeon Kim is to achieve so-called decoupling - stopping the US from coming to South Korea鈥檚 aid if and when Pyongyang decides it鈥檚 time to 鈥渞eunify鈥.
鈥淏ased on the North's public statements and their actions and their private comments, it appears that the nuclear weapons are for both deterrence and for potential use in forceful unification. That's something that they've talked about openly and in private.鈥
Myers agrees Kim鈥檚 nuclear weapons are about unification, but not necessarily by force.
鈥淣orth Korea needs the capability to strike the US with nuclear weapons in order to pressure both adversaries into signing peace treaties. This is the only grand bargain it has ever wanted.
鈥淭he treaty with Washington would require the withdrawal of US troops from the peninsula. The next step, as Pyongyang has often explained, would be some form of the North鈥揝outh confederation it has advocated since 1960. One would have to be very naive not to know what would happen next.鈥
The idea that poor, backward North Korea could impose unification on a modern, wealthy and militarily more advanced South appears preposterous, and maybe it is. But Bradley K Martin says, however unlikely, it remains Pyongyang鈥檚 objective.
鈥淚 have always believed reunification is their number one goal,鈥 he says. 鈥淢any people say they gave up on it long ago - they know they can鈥檛 do it. Those people underestimate the confidence you can build if you have the attention of a whole people. If you are running the propaganda system in a one-man dictatorship you can convince people they can do anything.鈥
I should be halfway to Beijing. Instead I am sitting in a drab room at a Pyongyang hotel. On the far wall portraits of Kim Il-sung and Kim Jong-il stare down. Right now, their expressions appear particularly malevolent.
I feel dazed, shell-shocked. Across the table a slender man with a face lined by years of smoking is looking at me with an expression of calm menace.
鈥淭his can all be over very quickly and you can go home,鈥 he says, rotating an unlit cigarette in his right hand. 鈥淚f you confess your crimes and apologise this will all be over. If you refuse, things will get much worse.鈥
An hour before, I had been at Pyongyang airport preparing to board a flight to Beijing. Now I am facing hours, possibly days, of interrogation.
My crime, according to my crinkle-faced interrogator, is 鈥渋nsulting Marshal Kim Jong-un鈥. The pit of my stomach turns cold.
This is a serious offence. I鈥檓 not sure how I鈥檝e done this. Nor, it becomes clear, is my interrogator. It doesn鈥檛 matter. My guilt has been decided elsewhere. Now he must get my confession.
As the night wears on the team changes and the threats become more frightening. A new interrogator stares at me with cold, malevolent eyes.
鈥淚 am the one who investigated Kenneth Bae,鈥 he says. 鈥淚 think you know what that means.鈥
I do. Kenneth Bae is a Korean-American pastor who was sentenced to 15 years hard labour by North Korea. He served 735 days before a deal was done for his release.
My interrogation was terrifying, but also surreal. I had been invited to Pyongyang to cover a visit by three Nobel laureates. Then I was detained and threatened with prison because the regime didn鈥檛 like what I鈥檇 written.
To me this seemed counter-productive. But I had fundamentally failed to understand my assigned role - to uncritically present North Korea鈥檚 version of the truth to the outside world. I had transgressed, I had become an enemy.
Weeks later in Seoul a senior North Korean defector explains.
鈥淵our crime was not just to criticise Kim Jong-un, but where you did it,鈥 he says. 鈥淚n his own capital.鈥
He is certain the only person who could have approved my detention, and release, was Kim Jong-un.
鈥淵ou were very lucky to get out,鈥 he says.
Prof Paik Hak-soon is the director of the Center for North Korean Studies at the Sejong Institute in South Korea. He also thinks I was lucky to get away with 鈥渙nly鈥 being expelled.
鈥淜im鈥檚 identity is that of a king,鈥 he says. 鈥淗is sense of self-esteem does not allow any criticism or opposition from others. Any person or country that challenges or opposes him, faces retaliation without fail.鈥
North Korea has a long history of detaining foreigners for minor transgressions. Kim Jong-un has a particular penchant for it. Since 2011, 12 foreign nationals and four South Koreans have been held by Pyongyang.
Three months before my detention in 2016, a young American tourist, Otto Warmbier, was sentenced to 15 years hard labour for stealing a propaganda poster from a hotel wall. His punishment seemed out of all proportion to his alleged crime.
Warmbier was eventually returned to the US with severe brain damage, and died a few days later. Most observers think his case is unusual. American captives are rarely physically abused - they are too valuable.
For Pyongyang, US detainees are pawns in a cynical diplomatic game. They force the US government to enter into long negotiations, and finally to send a high-profile envoy to seal the release in person. Former US President Jimmy Carter was one. In 2009 former President Bill Clinton went to Pyongyang to bring back two detained US journalists.
David Straub is a retired US diplomat who accompanied Bill Clinton on that trip.
"The North Koreans basically demanded Bill Clinton come and that was the only way that they would return the two journalists," he says. 鈥淚t was clear that North Korea just wanted to have a photograph of Kim Jong-il with Bill Clinton, so they could show their people and the world and feel good about having forced the US to bend to their will."
But what Kim Jong-un really wants isn鈥檛 an ex-US president. He has always wanted the real thing - face-to-face negotiations with a sitting US president.
On 9 May, US Secretary of State Mike Pompeo arrived in Pyongyang, his second trip in a little over a month. He met with Kim Jong-un, and was handed three US citizens held in North Korean custody.
The longest held was Kim Dong-chul, a 65-year-old Korean-American businessman who鈥檇 been in North Korean custody for 952 days. President Trump had asked for the three to be freed as a condition for holding a summit with Kim Jong-un.
As he greeted the freed detainees at Andrews Airforce Base the US president declared: 鈥淲e want to thank Kim Jong-un, who really was excellent to these three incredible people.鈥
Such hyperbole showed how eager Trump was for a first ever summit with the North Korean leader.
Kim Jong-un has achieved his goal.
For Pyongyang, US detainees are pawns in a cynical diplomatic game. They force the US government to enter into long negotiations, and finally to send a high profile envoy to seal the release in person. Former US President Jimmy Carter was one. In 2009 former President Bill Clinton went to Pyongyang to bring back two detained US journalists.
David Straub is a retired US diplomat who accompanied Bill Clinton on that trip.
"The North Koreans basically demanded Bill Clinton come and that was the only way that they would return the two journalists," he says. 鈥淚t was clear that North Korea just wanted to have a photograph of Kim Jong-il with Bill Clinton, so they could show their people and the world and feel good about having forced the US to bend to their will."
But what Kim Jong-un really wants isn鈥檛 an ex-US president. He wants the real thing, face-to-face negotiations with a sitting US president.
On 9 May, US Secretary of State Mike Pompeo arrived in Pyongyang, his second trip in a little over a month. He met with Kim Jong-un, and was handed three US citizens held in North Korean custody.
The longest held was Kim Dong-chul, a 65-year-old Korean-American businessman who鈥檇 been in North Korean custody for 952 days. President Donald Trump had asked for the three to be freed as a condition for holding a summit with Kim Jong-un.
As he greeted the freed detainees at Andrews Airforce Base the US president declared: 鈥淲e want to thank Kim Jong-un, who really was excellent to these three incredible people.鈥
Such hyperbole denotes how eager President Trump now is for a first ever summit with the North Korean leader. Kim Jong-un is very close to achieving his goal.
CREDITS
Author: Rupert Wingfield-Hayes
Online production: Ben Milne
Graphics: Joy Roxas
Photograph credits: Alamy; EPA; Getty Images; Reuters
Editor: Finlo Rohrer
Publication date: 23 May 2018 (updated 11 June 2018)
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