NEW YORK — When North Korean leader Kim Jong Un celebrated the launch of a powerful new missile last month, he was surrounded by a group of top scientists and officials. State media did not identify the men, but they have all been seen with Kim before.

These men have built an intercontinental ballistic missile that appears capable of hitting any city in the United States, a feat of physics and engineering that has stunned the world.

Kim has been ruthless about consolidating power, executing scores of senior officials, including his own uncle. But he has showered his regime’s scientists with incentives and adulation, turning them into public heroes and symbols of national progress.

“We have never heard of him killing scientists,’’ said Choi Hyun-kyoo, a senior researcher in South Korea who runs NK Tech, a database of North Korean scientific publications. “He is someone who understands that trial and error are part of doing science.’’

Analysts are still trying to explain how North Korea managed to overcome decades of international sanctions and make so much progress so quickly. But it is clear the nation has accumulated a significant scientific foundation despite its backward image.

Each of its six nuclear tests has been more powerful than the last, boosting Kim’s stature at home and his leverage abroad. Still, it is unclear if the North has mastered the technology needed to keep a nuclear warhead intact as it reenters the Earth’s atmosphere.

Kim has elevated science as an ideal in the regime’s propaganda and put his fondness for scientists and engineers on prominent display across North Korea. That is a departure from the practice of his predecessor and father, Kim Jong Il, who instead emphasized cinema and the arts as propaganda tools.

Four years after taking power in 2011, Kim Jong Un opened a six-lane avenue in Pyongyang known as Future Scientists Street, with gleaming apartment towers for scientists, engineers, and their families.

He also opened a sprawling complex shaped like an atom that showcases the nation’s achievements in nuclear science. Extravagant galas are held to celebrate scientific progress.

There is little doubt what is behind Kim’s passion for science. In ubiquitous propaganda posters, North Korean rockets soar into space and crash into the US Capitol.

And after successful tests, scientists and engineers are honored with huge outdoor rallies. On their way to Pyongyang, their motorcades pass cheering crowds.

“They are already pretty sophisticated in metallurgy, mechanical engineering, and to some extent chemistry,’’ all areas tied to the nation’s civilian and military needs, said Joshua Pollack, a senior research associate at the Middlebury Institute of International Studies at Monterey, Calif.

North Korea has imported scientific papers and journals from Japan for decades. And when it sends students abroad, it orders them to copy scientific literature and bring it home, said Michael Madden, who runs the North Korea Leadership Watch website.

UN sanctions prohibit the teaching of scientific material with military applications to North Korean students. Yet North Korea still sends students to countries such as China, India, and even Germany, according to analysts and UN reports.

The Internet has also been a gold mine for the North. While the state blocks public access, it allows elite scientists to scour the web for open-source data under the watch of security agents. The North has also built digital libraries of approved material that are accessible across the country.

North Korea funnels its top science students into military projects. Those selected for the nuclear and missile program are relocated from their hometowns and allowed to return for visits only with government minders, according to defectors and analysts.

But they are also given better food rations — and access to weapons designs and components obtained by the nation’s spies and hackers, who have focused on the former Soviet republics.

Analysts have identified six figures who have repeatedly appeared alongside Kim at key moments — four tied to missile development and two associated with nuclear tests.

Two members of the “missile quartet’’ are scientists, according to state media. Jang Chang Ha, is president of the Academy of National Defense Science, and Jon Il Ho, is commonly described as an “official in the field of scientific research.’’

Ri Pyong Chol appears to be the quartet’s highest-ranking member. A former air force commander, he serves as first deputy director of the ruling Workers’ Party’s munitions industry department.

Kim Jong Sik, 49, first began appearing with Kim Jong Un in February 2016 and has an engineering background. His rise has coincided with an acceleration of test launches, but he and Ri did not attend last month’s launch.

Ri Hong Sop, the director of North Korea’s Nuclear Weapons Institute, appears to be a leading figure in the nuclear program. He has been blacklisted by the United Nations since 2009.

Hong Sung Mu, the other member of the “nuclear duo,’’is a former chief engineer at the Yongbyon nuclear complex, the birthplace of the North’s nuclear weapons program.