The scientists are blacklisted across the globe but hailed as heroes in North Korea, where they are working around the clock to help make the country a nuclear superpower.
Photos released just hours ahead of last weekend’s nuclear test showed Ri Hong Sop and Hong Sung Mu flanking despot Kim Jong-un as he inspected a new peanut-shaped warhead.
Ri is the head of the hermit state’s Nuclear Weapons Institute while Hong is deputy director of the ruling Workers’ Party of Korea’s munitions industry department.
According to the United Nations, Ri is known to be “engaged in or providing support for, including through other illicit means, DPRK’s nuclear-related, other weapons of mass destruction-related and ballistic missile-related programmes”.
They said the 77-year-old is the “former director of Yongbyon Nuclear Research Center and oversaw three core facilities that assist in the production of weapons-grade plutonium: the Fuel Fabrication Facility, the Nuclear Reactor and the Reprocessing Plant”.
Several North Korea leadership experts say they are part of a cadre of weapons experts at the frontline of the young leader’s stated ambition: developing an intercontinental ballistic missile (ICBM) that can carry a nuclear weapon to the United States or Europe.
Compared to his father Kim Jong Il and grandfather Kim Il Sung who both preferred small working groups and middle managers to deal with weapons programmes, the current 33-year-old despot has been more personally involved with his team of nuclear scientists.
Expert Yang Moo-jin, professor at the University of North Korean studies in Seoul, said: “It appears that Hong is spearheading the nuclear development programme as a senior party official and Ri is in charge of nuclear tests such as hydrogen bombs on a working level.”
The two scientists have become increasingly high profile as Pyongyang’s weapons programmes have advanced at a rapid pace under Kim’s leadership.
In January 2016, Hong and Ri were the first and second in line to receive medals personally awarded by Kim at a ceremony to mark the country’s fourth nuclear test, state TV footage showed.
Two months later, they accompanied a smiling Kim inspecting a silver-coloured sphere, which the North said was a miniaturised warhead capable of being fitted to an ICBM.
And last weekend a huge nuclear test was carried out in North Korea, with rumours growing of another provocative launch set to take place in the near future.
Today America raised tensions further, accusing Kim of “begging for war” before warning “our country’s patience is not unlimited”.
The US ambassador to the United Nations Nikki Haley said: “His abusive use of missiles and his nuclear threats show that he is begging for war.
“War is never something the United States wants. We don’t want it now. But our country’s patience is not unlimited.”