What can China do about nuclear North Korea?

[daring dude]

Hong Kong (CNN)As world powers work to verify North Korea's claims that it has tested a hydrogen bomb, others are asking what the country's only real ally -- China -- will do.

On Wednesday, China's Ministry of Foreign Affairs released a statement that it "firmly opposes" this and any future nuclear tests by North Korea.

Spokeswoman Hua Chunying told reporters that Beijing had not been given advanced warning of the test and would be summoning Pyongyang's ambassador to lodge a protest.


Donald Trump: Let China deal with North Korea 01:28
Speaking to CNN's Wolf Blitzer on "The Situation Room" Wednesday, Republican presidential front-runner Donald Trump said that North Korea was Beijing's problem to fix.

"If they don't solve that problem, we should be very tough on them on trade -- meaning, start charging them tax or start cutting them off. You'd have China collapse in about two minutes," he said.

TIMELINE: North Korea's nuclear program

"If there was ever a moment for the Chinese to decide that now is the time that we really have to do something, this is it," said Mike Chinoy, former CNN international correspondent and the author of "Meltdown: The inside story of the North Korean nuclear crisis."

"The North Korean insult to China and Xi Jinping personally is really egregious. Xi Jinping is not a guy that takes this stuff lying down."

China condemns North Korea's test claims02:08
"The North Koreans really don't like the Chinese," said Chinoy.

"They resent the hell out of the Chinese. They hate the idea that the Chinese can come in and tell them what to do.

And the reality is the Chinese can't."

Relations between Pyongyang and Beijing have been frosty since Kim Jong Un succeeded his late father as dictator, promptly purging several key government figures -- such as his uncle Jang Song Thaek -- with strong ties to China.

Kim has never visited China as leader, nor has he met President Xi Jinping, despite reportedly lobbying to do so for several years.

North Korea's girl band abruptly leaves China01:58
China views Kim Jong Un as a "very rogue, irresponsible and brattish leader," said Lee Jung Hoon, professor of International Relations at Yonsei University.

Last month, Kim's personal Moranbong girl band flew to Beijing to play a series of shows, before abruptly canceling the tour and returning to North Korea.

A dispatch by China's state-run Xinhua news agency later cited "communication issues at the working level" as the reason for the cancellation, which came in the same week North Korea first claimed it had added the hydrogen bomb to its arsenal.



Why does China support North Korea?


"The relationship is basically dysfunctional, but it serves everyone's interests," said Jeffrey Lewis, director of the East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies.

North Korea serves as a buffer for China between it and key U.S. ally -- and mutual defense signatory -- South Korea.

More than anything else, Beijing wants stability on its border, which, nuclear tests notwithstanding, Pyongyang largely provides.

China perplexed by North Korea too 06:51
"What China does not want is a dramatic implosion of North Korea, or a kinetic weapons war on its doorstep," said Jasper Kim, director of the Center for Conflict Management at South Korea's Ewha University.

A strong nuclear weapons program strengthens Kim Jong Un's regime and stabilises his rule, making it far less likely that he could be overthrown -- from inside or out -- and plunge the country into chaos, potentially sending millions of refugees pouring across the Chinese border.

North Korea is also a major tool for Beijing "in the bigger chess game of U.S.-China relations in the Asia Pacific region," said Yonsei's Lee.

History also plays a part, though less and less as the current generation of North Korean and Chinese leaders are more detached from the Korean War, during which Mao Zedong sent troops to support Kim Il Sung.




Beijing's dilemma[/paste:font]


North Korea is one of the most sanctioned countries on Earth, with the United Nations, the U.S., European Union, and a host of other countries all imposing strict restrictions on doing business with the government or North Korean companies.

However, while Beijing has supported previous U.N. resolutions imposing greater sanctions, Chinoy says that actual "enforcement of sanctions on the Chinese side has not been that rigorous."

Kim Jong Un 'more dangerous and erratic than his father' 04:42
This lack of effective enforcement does mean there are steps that China could take immediately to up the pressure on Pyongyang, such as cutting off trade and oil links, and banning North Korean planes from entering Chinese airspace.

China could also stop state-owned and private firms from doing business in North Korea, such as in 2013, when the Bank of China stopped dealings with the North Korea Foreign Trade Bank, cutting Pyongyang off from a key source of foreign currency.

"My guess is China will do something tough and nasty but it won't be tough and nasty enough to make a difference," Chinoy said.


Source: North Korea nuclear test: What will China do? - CNN.com

 

[Shotgunner51]

CNN may ask this question: Is it a thermonuclear test?

Thermonuclear science, ICBM techs, are nothing new. A physics graduate somewhere in Tanzania may also claim enough knowledge on these, let alone highly intelligent North Koreans. However it's not hard to figure out that knowing something, and making it happen, are completely different concepts. That's why only less than a handful of nations have built such capabilities. So even if we wildly assume the North Koreans are capable of building a sophisticated industrial complex with deep supply chain of tools, machineries, components, fuel & electricity, where do they get the essential raw materials?​

But of course, there are game rules, so they will receive "condemnation" from Foreign Office of PRC.

US condemns ISIS 'mass execution' as White House signals Iran cooperation on Iraq - Telegraph​

 

[C130]

they can't do nothing. they use to have leverage over it's bastard child, but now since they got nuclear weapons and the missiles to carry them, they can black mail China like they are doing with South Korea and Japan.


if China thinks it can amass a 1,000,000 man army on North Korea border and remove the fat brat it's too late for that option. a nuke could be hurtling towards Beijing in minutes. even NK conventional ballistic missiles would do serious damage to China's army and it's population centers.


basically China has no leverage anymore.


the only option I can think off is wiping out the entire leadership with a small-yield nuclear device, and have paratroopers land and take over their military complexes.

 

[Dalit]

they can't do nothing. they use to have leverage over it's bastard child, but now since they got nuclear weapons and the missiles to carry them, they can black mail China like they are doing with South Korea and Japan.


if China thinks it can amass a 1,000,000 man army on North Korea border and remove the fat brat they wouldn't make it time. a nuke could be hurtling towards Beijing in minutes. even NK conventional ballistic missiles could do serious damage to China army and it's population centers.


basically China has no leverage anymore.

You are gravely mistaken. China isn't the US who will do anything foolish or rash to worsen an already volatile situation. China has the means to easily take care of NK. China is the only reliable ally of NK. They know their limitations. Throwing a nuke on China? LOL China has full leverage and control.

 

[C130]

You are gravely mistaken. China isn't the US who will do anything foolish or rash to worsen an already volatile situation. China has the means to easily take care of NK. China is the only reliable ally of NK. They know their limitations. Throwing a nuke on China? LOL China has full leverage.

if you can tell me how China can deal with NK I am all ears

and how it has leverage over it

 

[Dalit]

if you can tell me how China can deal with NK I am all ears

and how it has leverage over it

I already did. Like I said, NK won't force its hand by pissing off its only reliable ally China. The North Koreans go to extreme lengths to piss off the Americans, but know their red lines with regards to China. Be rest assured.

 

[C130]

I already did. Like I said, NK won't force its hand by pissing off its only reliable ally China. The North Koreans go to extreme lengths to piss off the Americans, but know their red lines with regards to China. Be rest assured.

trust me China is fed up with NK and it's new leader. NK is black mailing China 100%. If China thinks it's acceptable for a despot lunatic who now has the means to kill millions of lives (including Chinese) is alright because it pisses off the yanks, lol


are you telling me China needs a wild card a joker actually to keep the U.S off balance or win a potentional war?? c'mon.

I hope NK milks China for all she is worth.

 

[Dalit]

trust me China is fed up with NK and it's new leader. NK is black mailing China 100%. If China thinks it's acceptable for a despot lunatic who now has the means to kill millions of lives (including Chinese) is alright because it pisses off the yanks, lol


are you telling me China needs a wild card a joker actually to keep the U.S off balance or win a potentional war?? c'mon.

I hope NK milks China for all she is worth.

You really think that China isn't aware of the North Korean nuke program across its border? LOL they are fully aware and are playing their cards very deliberately. Like I said, China is in full control. Sometimes, an extra dose of fabricated chaos can be a blessing in disguise.

NK has no means to blackmail China which is its only reliable ally. Unless, NK wants to isolate itself completely. This is only a popular Western sentiment.

 

[desimorty]

the only option I can think off is wiping out the entire leadership with a small-yield nuclear device, and have paratroopers land and take over their military complexes.

Source: What can China do about nuclear North Korea?

What? The scale is far to large. Entire nation.
You wanna bring NK in, buy them out.
They did it with Pakistan. Guarantee the brat a position in Korea, and give them money.
Because military action would cost more than any amount of money.
I suspect, the kid only firming his position before droping or opening the drapes. Hes crazy, but he is only Human.

 

[Chinese-Dragon]

they can't do nothing. they use to have leverage over it's bastard child, but now since they got nuclear weapons and the missiles to carry them, they can black mail China like they are doing with South Korea and Japan.


if China thinks it can amass a 1,000,000 man army on North Korea border and remove the fat brat it's too late for that option. a nuke could be hurtling towards Beijing in minutes. even NK conventional ballistic missiles would do serious damage to China's army and it's population centers.


basically China has no leverage anymore.


the only option I can think off is wiping out the entire leadership with a small-yield nuclear device, and have paratroopers land and take over their military complexes.

Did they ever threaten to nuke China?

Whereas they threaten to nuke America every other day:

North Korea threatens US with nuclear attack | Daily Mail Online

North Korea issues nuclear warning to U.S. - CNN.com

Frankly, North Korean nukes are less of a threat to us than American nukes. At least the former are not pointed at us.

 

[atomix]

trust me China is fed up with NK and it's new leader. NK is black mailing China 100%. If China thinks it's acceptable for a despot lunatic who now has the means to kill millions of lives (including Chinese) is alright because it pisses off the yanks, lol


are you telling me China needs a wild card a joker actually to keep the U.S off balance or win a potentional war?? c'mon.

I hope NK milks China for all she is worth.

Dude China has full control over this idiot, if not for china he would have been gone long time back. Chinese just dont show it off.
Nuclear test is one way of taking away the focus from spratly island issue and another way of threatening with proxy.
China gains by this test as the focus will be on NK while they can speed up construction and solidify their position on the island.

 

[C130]

Did they ever threaten to nuke China?

Whereas they threaten to nuke America every other day:

North Korea threatens US with nuclear attack | Daily Mail Online

North Korea issues nuclear warning to U.S. - CNN.com

Frankly, North Korean nukes are less of a threat to us than American nukes. At least the former are not pointed at us.

not pointed at you i think they are pointed in every direction. you think having a unstable nation with nuclear weapons near youy border is good?? that closer than teeth and lips friendship was in the past


I don't think it's in China best interest for it's bastard child to threaten and dare I say launch a nuclear attack against some of largest trading partners (SK,Japan, and the U.S) and especially when the counter nukes start landing near their border

 

[CriticalThinker02]

not pointed at you i think they are pointed in every direction. you think having a unstable nation with nuclear weapons near youy border is good?? that closer than teeth and lips friendship was in the past


I don't think it's in China best interest for it's bastard child to threaten and dare I say launch a nuclear attack against some of largest trading partners (SK,Japan, and the U.S) and especially when the counter nukes start landing near their border

You really underestimate the Chinese if you think they are or were not aware of NK's nuclear program, just like how your country perfectly knows about Israels Nuclear Programs, how many nukes they have and what means of the delivery system they have in storage as you helped them acquire it yourself.

and I think North Korea perfectly knows who their friends and allies are, a whole nation cannot be stupid.

Oh and btw make sure next time you look in the mirror before you hope North Korea milks China for all her worth because Israel is doing the same thing to you by making sure you fight all of their wars all the time.

 

[Indiran Chandiran]

You really underestimate the Chinese if you think they are or were not aware of NK's nuclear program, just like how your country perfectly knows about Israels Nuclear Programs, how many nukes they have and what means of the delivery system they have in storage as you helped them acquire it yourself.

and I think North Korea perfectly knows who their friends and allies are, a whole nation cannot be stupid.

Oh and btw make sure next time you look in the mirror before you hope North Korea milks China for all her worth because Israel is doing the same thing to you by making sure you fight all of their wars all the time.

I , once read , that the game of weiqi involves surrounding ones opponents coins with ones own to the extent that the opposite no knows he's beaten , acknowledges the supremacy of the Victor & graciously concedes defeat .

Of course, the game itself is so subtle , that only ppl with mastery over weiqi know who's been licked & who's the Victor. May one also add that the loser is also expected to be a rational person & concede , saving his coins & curtailing unnesessary loses .

But , what if , instead of a rational player , one faces a suicidal opponent .Victory , itself would not be clean but extremely bloody & pyrrhic .

This lies at the heart of the dilemma that the US & its allies face in the far east .This also lies at the heart of the dilemma that India faces w.r.t Pakistan in S Asia.

Both NK & Pak , borrowing a leaf out Mao's China, are hamming to the hilt their suicidal image for incremental gains , however intangible .They also serve the purpose of China keeping the US & its allies ( here, I would also include India) constantly off guard while the Chinese consolidate their economy & essentially their military .both the Chinese & NK seen to be having a ball using each other in this great game .with Pak , it seems to be graduallly replacing the US as their principal benefactor & putting themselves right in the centre of Ind - Pak dispute , in spite of having a vested interest, much to India's discomfiture.As if saying to India , you have a problem with Pak , we're here to help .of course , on our terms & with you ready for sacrifices .India , as usual , seems to be prepared to take the easy way out .but , then again it seems to early to speculate on how far the Modi govt is willing to go to accommodate Pak & to a lesser extent China.


Part of the problem lies in the US & its European allies , unnecessarily tangling with Russia in its backyard making a foe out of them driving them reluctantly into the arms of the Chinese.Part of the problem also lies in the US & its allies letting pleasure get the better of their biz by engaging in Syria , Libya , thereby famously neutralizing the Bush axis of evil & withdrawing prematurely from Afghanistan & Iraq.

This also leaves the road right open to China to exercise its machinations .destiny seems to be on their side & they're definitely making the most of it .The All Sunni states alliance , the Saudi Iran rift getting deeper - all makes for disturbing prognosis .This complicated the OBOR & MSR for China too.

Right now the situation is in a flux.but expect more confusion before clarity emerges .The new incumbent to the white house would have his / her hands full but I expect some sort of agreement with Russia , thus earning Russias neutrality to the extent possible , which Prez Obama can't / won't conclude . As an aside he seems somewhere of a cross between Pt Nehru & Manmohan , someone who understands everything but does next to nothing , zealously avoiding maximising confrontation .He's not a wartime leader & the situation in Asia is fast approaching that , from ME to SA to FE.

To his credit , he can claim to having constructively engaged the Iranians - who now seem to have more in common with the US & its allies in Syria / Iraq than with the Saudis, though the chasm is still considerable but not in bridgeabe . He will , in future , also be remembered for the definitive break with the Saudis to whom the west extended blind suppport.

It's my belief that the situation in Asia has entered the endgame ,cutting a swathe across the ME , to SA , to EA. The stage seems also set for something definitive to happen to the Pak / NK nukes . though it's too early to speculate on the contours , such an engagement ( destructive ? / pay offs ? / sanctions ) , as the US & its allies would formulate , would take.

The US is deeply ambivalent about letting Japan exercise a greater degree of autonomy in its self defense .but every such grave provocation by NK in the FE & Pakistan in SA bring Japan & Ind respectively more & more closer to decisive action .In Japan's case it could mean going nuclear .In India's case , calling Pakistan's bluff & paying it back in its own coin & potently too.but , having said that, as I remarked earlier , its still early days in the endgame .

We , are indeed , living in interesting times .

 

[ashok321]

Behind North Korea’s Nuclear Advance: Scientists Who Bring Technology Home

https://www.wsj.com/articles/behind...al&utm_source=twitter.com&utm_campaign=buffer


HARBIN, China—When North Korea tested what it said was a domestically produced hydrogen bomb on Sunday—a week after launching its 18th ballistic missile of the year—it was a reminder of a conundrum at the heart of the country’s nuclear program. How has it advanced so rapidly despite concerted international efforts to keep weapons-related technology out of its hands?

The answer may lie in expertise brought home by North Korean scientists who studied abroad, especially in China, sometimes in apparent violation of 2016 United Nations sanctions that ban teaching North Koreans certain subjects.

Hundreds of North Korean scientists have studied outside the country in recent years, according to a Wall Street Journal review of official figures, academic papers and data from universities, many in areas the U.N. says could help Pyongyang’s weapons programs.

Early in its six-decade quest for a nuclear arsenal, North Korea relied on technology and experts from the Soviet Union, then later from Iran and Pakistan. That it can now draw on its own scientists indicates it will only become harder to contain Pyongyang’s nuclear ambitions.

“We should be very concerned about North Korean researchers abroad, particularly in China,” said Katsuhisa Furukawa, a member from 2011-2016 of the U.N. panel of experts monitoring sanctions enforcement on North Korea.

Among those scientists is Kim Kyong Sol, who was still at China’s elite Harbin Institute of Technology more than a year after the U.N. introduced its sanctions, doing a Ph.D. in mechatronics—a blend of mechanical engineering, electronics and programming—according to university staff. In March this year, he published a paper in China co-written by a senior engineer in Beijing’s military-run space program.

After reviewing Mr. Kim’s paper at the Journal’s request, Mr. Furukawa concluded it fell into a category banned by U.N. sanctions.

Foreign-educated North Koreans’ work in multiple disciplines, said Mr. Furukawa, now an independent analyst, has “surely contributed to the accumulation of scientific know-how and information relevant to its weapons program.”

North Korea’s technological advances go beyond nuclear science. Any research or contacts abroad that could help North Korea launch objects into space is of concern to the U.S. as it tries to stop Pyongyang from perfecting ways to attack America or its allies.

Pyongyang has launched Earth-observation satellites, which can be used for reconnaissance and targeting. It has also test-fired missiles from a submarine and said it could conduct an electromagnetic-pulse attack, designed to cripple electric grids by detonating a nuclear device on a satellite.

The technology Mr. Kim studied, called MR damping, can be used to stabilize spacecraft and absorb shock in missile-launch systems, including in submarines, as well as to reduce vibration in cars, buildings and helicopters, U.S. experts in the field said.

Kim Kyong Sol’s entry in a registration book at his former accommodation block at Harbin Institute of Technology. PHOTO: JEREMY PAGE/THE WALL STREET JOURNAL

Mr. Kim returned home in June, university staff said. He didn’t respond to emails. China’s foreign ministry said Beijing was “strictly implementing” all U.N. resolutions on North Korea. It didn’t respond to questions about Mr. Kim, nor did Harbin Institute of Technology.

The concern among U.S. officials is that Pyongyang exploited a lack of strict education sanctions before the 2016 U.N. ban to dispatch scientists and bring back “dual use” expertise—with civilian and military applications—and could continue to benefit from any lax enforcement of the ban.

Some of those officials said they fear that even with strict sanctions enforcement, Pyongyang may already have sufficient indigenous know-how for its nuclear goals. There is evidence North Korea produces its own rocket engines, the Journal reported in August, citing a U.S. intelligence official, contradicting a recent think-tank report suggesting its engines are from Ukraine or Russia.

Homemade claims

Advanced Studies

Hundreds of North Korean scientists have studied abroad or collaborated with foreign scholars in recent years, some in fields subject to 2016 U.N. sanctions.

Number of research papers by North Korean academics in the Web of Science Core Collection*, 2006-2016

60

50

40

30

20

10

0

2006

’09

’08

2010

’12

’13

’14

’15

’07

’16

’11

Research fields of North Korean academics in the Web of Science Core Collection, 2011-2016

Materials science (23)**

Mathematics, applied (20)

Mathematics (20)

Optics (19)

Physics applied (13)**

Engineering, electrical/electronic (13)**

Metallurgy/metallurgical engineering (11)**

Physics, multidisciplinary (10)**

Mathematics applications (9)

Geology (9)

Other 75 fields (174)

*The Web of Science Core Collection is a database of information from more than 18,000 major academic journals

**All or partly banned by the U.N. for training or teaching to North Korean nationals

Source: Geum Hee Jeong and Sun Huh; Hallym University (co-authoring and research fields); U.N. Security Council Resolutions (U.N. banned subjects)


Kim Jong Un made a point of bragging that his claimed hydrogen bomb was indigenous: “All components of the H-bomb were homemade and all the processes ranging from the production of weapons-grade nuclear materials to precision processing of components and their assembling,” the nation’s official Korean Central News Agency quoted him as saying.

Following North Korea’s second nuclear-bomb test in 2009, the U.N. in a package of sanctions in response called on countries to “prevent specialized teaching or training” within their territories or by their nationals that could help Pyongyang’s nuclear and missile development.

The U.N. imposed the 2016 ban on teaching specific subjects in response to a fourth nuclear test in January of that year and broadened it to encompass disciplines such as advanced engineering and materials science after another test last September.

In a report this February, U.N. experts said they found several North Koreans studying physics in Italy and four studying material science, engineering and electronic communications in Romania last year after the ban. The report said all were redirected to permitted subjects. The institutions didn’t respond to requests for comment.

In 2016, U.N. experts said two North Koreans were training that year before the ban at an Indian space technology center where 32 others had attended since 1996, including one who recently headed Pyongyang’s satellite control center. The Indian center said it no longer accepts North Koreans.

China in recent years has accounted for the bulk of North Korean scientists abroad, the Journal found in a review of official figures and data from universities in countries where the most North Koreans typically have studied. In China, 1,086 North Korean postgraduates studied in 2015, the last year for which official data are available, according to a Chinese Ministry of Education publication, up from 354 in 2009. The publication doesn’t show which schools they attended or what they studied.

The Education Ministry didn’t respond to requests for comment.

Scholarly Exchange

China has accounted for many North Korean academics studying abroad or collaborating with foreign scholars.

North Korean postgraduates in China, 2006-2015

With Chinese government scholarship

Without Chinese government scholarship

1,100

1,000

900

800

700

600

500

400

300

200

100

0

’12

2010

’07

2006

’13

’11

’15

’14

’09

’08

Number of papers North Koreans co-authored with academics from other countries in the Web of Science Core Collection*, 2011-2016

China (114)

Germany (29)

Australia (4)

Italy (4)

United States (3)

Other 24 countries (35)

*The Web of Science Core Collection is a database of information from more than 18,000 major academic journals

Source: Ministry of Education of China (North Korean postgraduate numbers); Geum Hee Jeong and Sun Huh; Hallym University (co-authorship)


China accounted for 60% of research papers by North Koreans in foreign journals from 2011 through 2016, mostly in physics, engineering, math, metallurgy and materials science, a study of academic databases by researchers from South Korea’s Hallym University found.

Papers published by North Koreans in China since the 2016 U.N. sanctions span civilian fields such as medicine and mining but also include several in fields now prohibited, including metallic foams that protect against radiation.

Sending more scientists abroad, and giving them perks at home, has been central to Kim Jong Un’s policy of byungjin, or parallel progress, to develop nuclear weapons and the economy—a policy he introduced publicly after taking power on his father’s 2011 death.

North Korea has said it needs nuclear weapons to prevent an attack by the U.S. It began its nuclear-arms program with Soviet backing in the 1950s and for years had small exchanges of scientists with the Eastern Bloc. After the Cold War’s end, Pyongyang traded for nuclear and missile expertise, mainly with Iran and Pakistan, according to historians, while continuing to send a few scientists abroad.

Since North Korea’s first nuclear test in 2006, U.S. and U.N. sanctions have focused on curbing the flow of money and dual-use materials to Pyongyang’s weapons programs. The regime has compensated by trying to develop more indigenous weapons know-how, experts on North Korea said.

Kim Jong Un’s byungjin policy has helped Pyongyang develop a wide spectrum of technical expertise—including metallurgists to make strong, lightweight alloys for rockets, mathematicians to help guide missiles and satellite engineers to improve targeting and reconnaissance, said experts and Western government officials.

A team member of an intelligent-vehicle club at Harbin Institute of Technology, October 2016. PHOTO: WANG KAI/XINHUA/ZUMA PRESS
Mr. Kim’s studies
It isn’t clear how the mechatronics scientist, Mr. Kim, planned to use his expertise in MR damping. “Could it be turned into military applications? Possibly,” said Mehdi Ahmadian, a Virginia Tech professor who said he had done similar research on MR damping in space structures, which could include satellites, antennas or mirrors.

Footnotes in the paper Mr. Kim published show funding came from a project led by his Chinese supervisor, Chen Zhaobo, on hypersonic vehicles, which can fly at more than 3,800 mph and are being developed by China, Russia and the U.S. to deliver nuclear or conventional weapons.



What a War With North Korea Might Look Like

As tensions rise around the Korean Peninsula, American leaders have been openly discussing what was once unthinkable: A military intervention in North Korea. If this were to happen, here’s how specialists on North Korean security see things playing out.
Prof. Chen said that, after four years in Harbin on a Chinese government scholarship, Mr. Kim returned home because of the sanctions shortly before defending his Ph.D. thesis. “I tried to comfort him a little,” Prof. Chen said. “He knew that after going back, he’d feel disappointed. He didn’t express it, but you could still tell.”

He said Mr. Kim didn’t have access to secret Chinese defense technology but said his former student’s work, with further development, had potential civilian and military uses, including in space. He and two other professors who worked with Mr. Kim said they learned of the U.N. sanctions from students and colleagues only around May or June of this year.

Mr. Kim arrived as part of a cooperative agreement of the type several Chinese universities have signed since 2010 with North Korean universities, including two that U.N. experts have reported provide personnel and technology for Pyongyang’s nuclear-weapons program. They are Kim Il Sung University and Kim Chaek University of Technology, Mr. Kim’s alma mater.

David Albright, a former U.N. weapons inspector and expert in nuclear proliferation, said it is common among nations seeking to develop weapons of mass destruction to seek knowledge abroad, including by sending scientists to take courses and attend conferences. China’s engineering schools and training programs, he said, offer “opportunities to mingle with people who may have sensitive information, such as Chinese who have been in military programs.”

At the controls of a robot at Harbin Institute of Technology, May 2016. PHOTO: WANG KAI/XINHUA/ZUMA PRESS
The Harbin university, known as HIT, is one of China’s top engineering schools and conducts classified defense and space-related research, as well as regular civilian studies. The school has cooperation agreements with Kim Chaek and Kim Il Sung universities, which in 2013 sent the first group of 12 doctoral and postdoctoral students to enroll there, according to the HIT website. That number increased to 28 by 2015.

Mr. Kim was in the first group. Born in 1975, he studied mechanical engineering in North Korea before enrolling in HIT’s School of Mechatronic Engineering, according to his research papers. The school boasts on its website it has trained personnel for China’s manned space program and has facilities for defense research, including on ultraprecision machining.

Mr. Kim and the other North Koreans at HIT kept low profiles, sharing two-bedroom apartments and rarely socializing, university staff said. The North Koreans all had Chinese government scholarships, they said, which provided free housing and tuition and monthly stipends of about 3,000 yuan ($450).

“They were easy to recognize from their clothes and their looks,” said one Chinese postgraduate student at HIT. They appeared to be supervised by one individual among them, other students said.

Upon arrival, Mr. Kim “looked at the direction of my research and thought it was quite interesting,” said Prof. Chen, a vibration-control expert who has worked on defense projects. He said he now focuses on civilian research because “military project management is very strict and not conducive to academic exchanges.”

In 2007, Prof. Chen co-wrote a paper on designing composite laminates to control vibration in spacecraft. From 2012-2015, he ran a project on vibration control for hypersonic vehicles, according to his profile and the National Natural Science Foundation of China.

That project sponsored Mr. Kim’s paper in March, whose co-authors included Wang Xiaoyu from the Beijing Institute of Spacecraft System Engineering, which has worked on Chinese satellites and China’s manned spacecraft and lunar rover. Ms. Wang declined to comment.

Prof. Chen said Mr. Kim’s work was more directly related to helicopters but could be used in multiple fields. He and Mr. Kim applied for a patent in February, saying their technology has applications in areas including aerospace, according to China’s patent registry.

Norman Wereley, a University of Maryland aerospace-engineering professor and MR-damping expert, said Mr. Kim’s research was fairly basic but would allow him to do more sophisticated work at home. “He could think about, ‘well, hey if I want to do vibration control in a missile system, I have a much better understanding of how to do that,’ ” he said. “I don’t think he’s getting this education for scholarly reasons.”

At least 11 other North Korean Ph.D. students left HIT in June, while others switched to subjects such as management studies that aren’t banned by the U.N., university staff said.

Some may have taken home a little extra know-how. North Koreans are suspected of violating library regulations by downloading tens of thousands of papers from subscription-based databases in recent months at at least two Chinese schools, including HIT, according to university staff and students.

On May 16, 57,000 papers were downloaded by nine foreign students from the mechatronics and other faculties at HIT, according to a notice from its library. Staff and students said the culprits were North Korean.