North Korea has a flurry of new missile tests, including what it calls hypersonic weapons, underscored the importance of the country's missile engineers and scientists, a group that is high profile within his government but opaque to outsiders.
Analysts say Kim Jong Un appears to be taking measures to institutionalize the missile forces, signalling his intent to make them a long-term, operational part of his military plans. Here is what we know and what we don't about these key personnel.
There is very little known about the names and positions of the mid-level and working-level scientists and technicians involved in missile research and development.
They appear to have guaranteed job security because of the resources and effort expended to educate and train them, and they are sequestered to special districts, so they are not a political or social nuisance to the regime, according to analysts.
Michael Madden, North Korea leadership expert at the Washington-based Stimson Center, said this is a population that is not easily replaced by economic cadres or even military commanders.
Many of them attend Kim Jong Un National Defense University, a training ground for North Korean defense-related science and technology specialists, which has reportedly added a college focused on hypersonic missile technology. According to Ken Gause, director of the International Affairs Group at CNA, a nonprofit research and analysis organization in Arlington, Virginia, the scientists and engineers often appear to be split into competing teams designing similar types of weapons, allowing them to go down multiple routes to see which technology is the most promising.
A 2018 study by the James Martin Center for Non-proliferation Studies CNS found that North Korean scientists had collaborated with researchers in other countries to write 100 published articles that had identifiable significance for dual-use technology, weapons of mass destruction, or other military purposes.
Kim Jong Un relies on three top people to lead the secretive country's rapidly accelerating missile program.
They include Ri Pyong Chol, a former top air force general, Kim Jong Sik, a veteran rocket scientist, and Jang Chang Ha, the head of a weapons development and procurement center.
A fourth official - Pak Jong Chon, the Chief of the General Staff - has also assumed a higher-profile role in the Military Industry Department MID, which is responsible for the production of strategic weapons, Gause said.
Gause said there have been a lot of changes in the military industry over the last few years.
Pak oversaw a number of recent tests in the absence of Kim Jong Un, who did not attend any missile launches in 2021, before observing one of the hypersonic missile launches in January.
The appointment of Yu Jim to lead the MID last year. In the past, Yu was a representative of North Korea's primary state arms dealer in Iran, Madden said.
The Second Academy of Natural Sciences SANS oversees North Korea's missile development, and is known as the Academy of National Defense Science NADS.
Madden said that the state of a weapon development can often be divined from who has attended a test.
For example, an event where the only personnel are from NADS SANS means that the system is still in the research and development phase. When a NADS event combines with the 2nd Economic Committee, that often means that the system is moving from development to production and manufacturing.
This usually indicates that the system is completed and will be deployed if the military s General Staff Department GSD personnel attend a test, such as the recent train mobile missile.
As North Korea completes its missile and nuclear arsenal, it may fold more elements of its Strategic Forces back under GSD, signalling it has moved to an operational role, Madden said.
North Korea's missile program is based on the assistance it received from the Soviet Union, and later Russia, analysts say, and the boosters involved in propelling the latest hypersonic warheads are similar to Soviet designs.
There is debate over how much assistance has been provided since the 1990s.
According to the latest sanctions designations by the United States, North Koreans linked to the NADS in China and Russia continue to provide materials and technical information for North Korea's WMD and missile programs, aided by at least one Russian telecommunications company and a Russian national.
Markus Schiller, a Europe-based missile expert, said that North Korea's success in testing shows that it has had external support.
The younger Kim was testing more homegrown designs than his predecessors, according to Schiller, who notes that under Kim Jong Un, North Korean missiles failed more often than in the past.