Kim Jong Un is doing everything he can to keep North Korea’s youth in line

He is particularly worried about the foreign media trickling into his information-repressed country, affording North Koreans a rare glimpse into the outside world via Hollywood films or K-pop albums. Possessing or distributing such content—which Kim refers to as “dangerous poisons"—carries ever-stiffer penalties, even death.

At risk is Kim’s ability to maintain the illusion of North Korea as a socialist paradise, which is key to his ability to maintain power. And no group is more vulnerable to ideological slippage than North Korea’s youngest citizens.

That is why Kim has handed a central propaganda role of late to the Paektusan Hero Youth Shock Brigade. Named for the country’s sacred mountain, the group of teenagers and 20-somethings has been recently hailed as national heroes for helping to rebuild a western border region leveled by summer floods. Over four months, they erected 15,000 houses, schools and hospitals, the country’s state media claimed.

The youth shock brigade’s 300,000 members—about the population of Pittsburgh—had reportedly mobilized at a moment’s notice and volunteered to go, state media said.

In a speech last month, Kim, who calls himself the group’s “benevolent father," showered the fresh-faced members with praise, having earlier challenged them to express their regime loyalty by carrying out the manual-labor project.

The construction work, Kim was quoted as saying in state media, had represented a “good opportunity for training our young people to be staunch defenders and reliable builders of socialism."

North Korea’s highest legislative body, the Supreme People’s Assembly, offered tributes to the nation’s “grand construction campaign" that demonstrated the “spirit of our state," according to a Friday state media report.

“Kim Jong Un wants to get young people occupied with labor to stop them from getting together to watch South Korean television and develop heretical ideas about the state," said Peter Ward, a research fellow at the Sejong Institute, a think tank in Seoul.

Kim has a long list of challenges. He must avoid backlash, internally and externally, over his deployment of 12,000 troops to Russia. He is propping up a crumbled economy through sanctions-violating behavior. And he must decide how to approach four more years with President Trump, who in a Thursday interview with Fox News vowed to reach out again to the North Korean leader.

But keeping North Korea’s youngest generation as true believers represents a long-term challenge that he must address now. Indoctrinating the country’s youth ensures his regime’s survival for decades; losing the propaganda campaign may create domestic instability or invite scrutiny over his decisions, security experts say.

Kim’s decision a year ago to abandon hopes of peaceful reunification with South Korea and declare Seoul as North Korea’s new No. 1 enemy indicated how seriously he considers foreign influence as a threat. In recent years, Kim moved to also ban the use of South Korean fashion such as miniskirts or expressions like nam-chin, a shortened way to say boyfriend in South Korea. The country instituted shoot-on-sight orders at the border and erected barriers to block North Koreans from leaving—and outside information from coming in.

Young men have military conscriptions of at least a decade, where they are subjected to daily indoctrination lessons. Loyalty appears high among those soldiers fighting in Russia, based on interrogations of captured troops and writings found on slain combatants. But that still leaves women, school-age youths and men ineligible for conscription due to illness, short height or physical impairment.

The Paektusan Hero Youth Shock Brigade is one of the dozens of paramilitary organizations composed of North Koreans plucked from their everyday jobs to accelerate major construction projects under harsh conditions. Shock brigades were workforces organized in socialist states such as the Soviet Union to overcome the lack of advanced machinery.

While some voluntarily join shock brigades, many others are recruited forcibly and face widespread malnutrition, according to a South Korean government report from 2023, which interviewed North Korean escapees.

The work conditions can be dangerous. About two years ago, North Korean state media praised an 18-year-old “virgin girl soldier" who it said died from working despite emergency surgery, building a massive greenhouse at record speed. She had reportedly written in her diary an apology to Kim for failing to fulfill her daily tasks.

Cho Chung-hui, who escaped North Korea in 2011, was drafted more than four decades ago into a youth shock brigade. He was 17 years old at the time, coming from a lower social rank in North Korea’s songbun system. Joining the brigade was one of the few ways to gain Workers’ Party membership that could offer him a higher place in society.

Construction began before sunrise and often lasted until midnight, Cho said. Once during tunnel excavation, the walls collapsed on Cho, leaving him with an injured back. Some of his fellow workers died while others suffered broken legs or wrists, he recalled. When he was dispatched to a railroad construction site, workers slept in makeshift tents in the cold.

“I had maybe 10 days off a year," Cho, now 61, said. “I only learned about the five-day workweek when I came to South Korea."

North Korean media exhaustively covered the work of the Paektusan Hero Youth Shock Brigade after they were deployed to help the flood-hit North Pyongan province, which borders China in the country’s northwest. There were monthly updates on the young workers’ activities, praising them as patriotic and motivated.

The membership of youth shock brigades changes depending on who is available to be drafted, but whatever the exact makeup of these groups, the Kim regime has found them to be effective in indoctrinating North Koreans to blindly follow orders, said Kim Young-soo, head of the North Korea Research Institute in Seoul.

“The youth members may change," he said, “but the purpose of a shock brigade never changes: to prove loyalty to the Kim regime."

Soobin Kim contributed to this article.

Write to Dasl Yoon at dasl.yoon@wsj.com