SEOUL, South Korea — The quality of the thousands of North Korean troops preparing to join Russia’s war against Ukraine is coming under intense and generally unfavorable scrutiny.

North Korean soldiers are “mostly poorly equipped, unmotivated and undernourished,” a British academic said. They “appear relatively short and slightly built, reflecting widespread malnourishment,” a leading U.S. newspaper reported. They boast “no experience whatsoever” in “any form of combat,” a noted military historian said.

Some say Ukraine and the West denigrate the quality of the North Korean soldiers at their peril.

“It is absurd how they underestimate the North Koreans,” said Chun In-bum, a retired South Korean general who led the Special Forces Command. “I think they will be a shock to the Western world.”

Grant Newsham, a retired U.S. Marine officer with decades of experience in the Indo-Pacific theater, said: “Asian troops can fight. You’d think people would have learned this by now. Korean War veterans understood this, as did American and British forces in World War II. Vietnam? Same thing.

“This doesn’t mean they can’t be defeated — and badly — but it does mean they should not be underestimated,” Mr. Newsham said.

Japan, South Korea, China and Taiwan have emerged as economic powerhouses in East Asia in the decades after World War II. Asian military forces have also proved formidable despite sharing many of the perceived “weaknesses” of North Korean troops.

Defying Western skepticism over motivation, cohesion, fieldcraft, stamina and the willingness to take casualties, Asian troops have historically outperformed expectations, even when outgunned and undersupplied. The social glue binding ethnically homogenous nations offers one advantage, said Drew Thompson, a China expert and senior fellow at Singapore’s S. Rajaratnam School of International Studies.

“That points to the leveraging of monocultures for security purposes,” he said. “Social cohesion creates a sense of unity and an ability to mobilize economies and societies effectively for war.”

Gastone Breccia, a military historian at the University of Pavia, cited five factors in the effectiveness of East Asian military forces: discipline, resilience, expendability, numbers and resourcefulness.

From the Japanese victory in the 1904-1905 Russo-Japanese War to the North Vietnamese victory over U.S. forces in Vietnam, the 20th century offers numerous reasons to believe the North Korean forces in Ukraine could provide a major boost to Russia and major headaches for Ukraine and the United States.

Track record

A fortress state long isolated and economically backward, North Korea nevertheless fields a formidable fighting force. The regime of North Korean leader Kim Jong-un devotes an estimated 27% of gross domestic product to defense, financing a military force of 1.2 million active personnel and hundreds of thousands of reserve troops. In a country of just over 26 million people, it is the world’s fourth-largest military.

Analysts also doubt claims that the troops lack motivation.

“From 5 years old, North Koreans are indoctrinated, and when they turn 17, they go into the military,” said Mr. Chun. “What else do these young men know?”

North Korean commandos who infiltrated South Korea from the 1960s through the 1990s fought to the death when cornered or managed to evade massive cordons to get back across the border. Operatives who bombed a Seoul delegation in Burma, now Myanmar, attempted suicide when facing capture in 1982.

Pyongyang wields harsh coercive power. Mr. Thompson said, “There is family back home being held hostage.”

Military service has rewards in North Korea.

“Look what North Korea has done to their national heroes, all those old guys with those absurd medals on their chests,” said Mr. Chun. “Young kids see them and think, ‘If I die, my family will be taken care of.’”

Reported Russian payments worth $2,000 to $3,000 per soldier are huge sums for North Koreans, he said.

“Even if their government takes most and they only get $200 or $300, that is hundreds of times what a North Korean soldier makes at home,” said the former general.

North Korean commanders and troops have shown a historic willingness to accept high casualty rates in battle.

“One reason why South Koreans respect North Koreans … is because of their fanaticism and purported willingness to suffer enormous casualties to achieve goals,” said Douglas Nash, a retired U.S. Army colonel.

The U.S. and South Korea estimate that 10,000 to 13,000 North Korean troops have been deployed in Russia for training and possible imminent assignment to the front lines, enough to form three infantry brigades and one special forces brigade. That’s minor for Mr. Kim’s overall army, but in places such as Kursk, where some 30,000 Ukrainian troops are struggling to hold a Russian enclave seized in a surprise sortie last month, 10,000 fresh troops represent a significant mass.

“Expendable, well-disciplined, thoroughly indoctrinated infantrymen are worth three times their number on the battlefield,” Mr. Breccia said.

Experience

Doubts that the North Korean soldiers lack overseas combat experience should also be taken with a grain of salt. North Korean pilots deployed to the Vietnam and Arab-Israeli wars in the 1960s and 1970s, military advisers operated in Africa in the 1980s, and North Korean commandos are thought to have fought in Syria as “militias” in the 2000s. The North can draw on a huge pool of recruits with at least some military experience.” Some North Korean units are used for labor and agriculture, but all men serve 10 years in uniform.

“North Korean soldiers are not likely to be as professional as Western soldiers,” said Mr. Chun. “But for a conscripted military, they are motivated and indoctrinated.”

Even the widespread stories of physical limitations of North Korean soldiers raised among property and privation may not be accurate. In 2017, a malnourished North Korean soldier infested with intestinal parasites defected across the DMZ. Neither condition prevented him from charging through a hail of fire; he survived five close-range gunshot wounds.

Mr. Chun said the North Korean troops sent to Ukraine will unlikely experience ration shortfalls in grain-rich Russia.

“The North Koreans have planned this,” said Mr. Chun. “There was plenty of time to prepare and weed out the weak.”

Mr. Thompson suggested that, unlike the wars of the past century, North Korean troops will face a real challenge fighting far from home on unfamiliar terrain.

He noted that they train in North Korea’s harsh seasons. They are cold-weather capable, and winter favors the offensive in Russian military strategy. Frosted ground enables off-road armored maneuvering, while defenders have difficulty digging positions. North Korean troops also use the same Warsaw Pact standard arms deployed by both sides in Ukraine, including rifles and artillery.

Still, even those who say the North Koreans could prove formidable fighters acknowledge the mission’s challenges. North Koreans have no experience with joint operations and face language and procedural barriers that could be exposed on Ukraine’s high-tech, networked battlefield.

“Interoperability is going to be a challenge, but they can overcome that with liaison and good planning,” said Mr. Chun. “They will not be accustomed to drones, but if they are able to overcome the initial battle shock, Ukraine is in trouble.”