North Korean leader Kim Jong Un has a trio of close allies helping to advance his weapons programme
Images showing the young ruler laughing and celebrating with the trio of aides are often circulated by state-controlled media following a reportedly successful missile launch.
Now South Korean officials revealed who the three men are, and how they are advancing the rogue state's military arsenal.
An Chan-il, a North Korean defector who now runs a think tank in Seoul, said: "Rather than going through bureaucrats, Kim Jong Un is keeping these technocrats right by his side, so that he can contact them directly and urge them to move fast.
"It reflects his urgency about missile development."
Unlike his father Kim Jong Il, Kim Jong-un has not built a top team from North Korea's ruling elite, but has instead cherry-picked three experts from lower down the hierarchy as his closest allies.
And their friendly, jokey behaviour in the presence of the leader is at odds with the deferential body language of other key members of staff, who bow to Kim and speak to him with their hands over their mouths.
A South Korean official who did not want to be named said: "Kim Jong-un is raising a new generation of people separate from his father's key aides."
The three men will be of interest in the United States, as defence officials monitor the hermit state’s nuclear weapons programme.
Kim laughs alongside Ri Pyong Choi, left, dubbed by experts as 'the Big Potato'
The first and most prominent member of the trio is Ri Pyong Chol, dubbed "the Big Potato" by North Korea expert Michael Madden.
Mr Madden said: "He's been around since before Kim Jong Un was even talked about with any seriousness."
A former army general, Ri was born in 1948 and was educated for a while in Russia.
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He came to prominence in the early 2000s, at the same time Kim Jong Un started to emerge as his late father Kim Jong Il's most likely successor.
Today he is the deputy director of the Workers' Party Munitions Industry Department, which oversees the country's ballistic missile programme and was blacklisted by the US Treasury in 2010.
He is apparently always smiling in photographs, and was pictured accompanying Kim Jong Il on a visit to a Russian fighter jet factory in 2011 – the year of the former despot's death.
Kim Jin-moo, an expert on North Korea's elite and former government think tank analyst in Seoul, said Ri “looks like the party's guy in the missile programme”.
Kim Jong Un with Kim Jong Sik, second left, Ri Pyong Chol, third left, and Jang Chang Ha, right
The big potato in that trio of people is Ri Pyong Chol. He's been around since before Kim Jong Un was even talked about with any seriousness
North Korean leadership expert Michael Madden
The second man is rocket scientist Kim Jong Sik, a former civil aeronautics technician who now appears to work with Ri in the munitions department.
He won favour with Kim Jong Un following North Korea's first successful missile launch in 2012.
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After North Korea's recent series of ballistic missile test, dictator Kim Jong-un is often photographed with the same three men
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Kim Jong-un reacts during the long-range Hwasong-12 (Mars-12) strategic ballistic rocket test launch with Ri Pyong Chol (2nd L), Kim Jong Sik (C) and Jang Chang Ha (2nd R)
Mr Madden said: "When that thing went off and entered into a lower earth orbit, he got credit for that.
"The nuclear and missile guys under Kim Jong Un are getting their jobs based on merit.”
He has been photgraphed accompanying the ruler through the control room of North Korea's official space agency, the National Aerospace Development Administration (NADA), ahead of February's successful long range rocket launch.
Like Ri, Kim Jong Sik is also know to have travelled on Kim Jong Un's private plane, Goshawk-1 – a privilege rarely afforded to other officials.
An image of an undated missile launch released by state media
The third and final member of the trio is also the most mysterious: Jang Chang Ha, president of the Academy of the National Defence Science.
Another organisation blacklisted by the US Treasury, Jang reportedly overseas a staff of 15,000 working on developing the country's defence system.
According to the US Treasury, that system includes "missiles and probably nuclear weapons".
North Korea's banned weapons programme began in the early 2000s with a similar trio of men close to the leadership who specialised in procurement, science and military affairs.
Kim Jong Un has cherry picked his own top team of experts
Of them, logistician Jon Pyong Ho has died. The others – scientist So Sang Guk and military coordinator O Kuk Ryol – are elderly and no longer in the public eye.
Mr Madden said those three have been replaced by Kim Jong Un's hand-picked men.
He said: "These are the men bringing North Korea's missile programme into the 21st Century.”