South Korean troops returning from Vietnam are hailed by citizens in this March 1973 file photo. Korea Times file

South Korea's troop deployment between 1965 and 1973 to fight alongside U.S. soldiers in the Vietnam War has left a complex legacy. While it contributed to the modernization of South Korea's military and weapons systems, it also resulted in traumatic experiences for Vietnamese civilians. This was highlighted in a recent legal battle filed by a Vietnamese victim of wartime atrocities.

In January, the Seoul Central District Court ruled in favor of Nguyen Thi Thanh, who sued the South Korean government over a massacre committed by South Korean marines in her village in 1968. The ruling underscored the lasting wounds left by South Korea's military presence in Vietnam.

At the same time, the Vietnam War played a crucial role in advancing South Korea's defense capabilities. "South Korea's military learned valuable lessons from its direct involvement in the Vietnam War. In addition to gaining combat experience, South Korea was able to manufacture and export M16 rifles — the country's first domestically produced weapon — thanks to technology transfers from the U.S.," said Park Bum-jin, a retired Navy captain and professor at Kyung Hee University.

Park suggested that North Korean leader Kim Jong-un may have been inspired by South Korea's past strategy when proposing to send troops to support Russia in the war against Ukraine. In late 2024, approximately 12,000 North Korean troops were deployed to Russia's Kursk region, with around 4,000 reported killed or wounded.

According to Park, Kim likely sought to elevate North Korea's military capabilities by leveraging Russia's advanced technology. "There is strong evidence that Kim has focused on three key pillars of North Korea's weapons program: nuclear submarines, surveillance satellites and intercontinental ballistic missile (ICBM) technology," he said. "These are critical areas in which North Korea desperately seeks upgrades with Russia's assistance."

As the war in Ukraine enters its third year, experts are evaluating the potential benefits and drawbacks for North Korea following its large-scale troop deployment. Hopes for a ceasefire have emerged, with Ukraine expressing readiness to sign a deal brokered by the U.S. However, Russia has yet to agree. During a phone call with U.S. President Donald Trump on Tuesday, Russian President Vladimir Putin declined to sign the ceasefire agreement but agreed to halt attacks on energy infrastructure. Negotiations are set to continue.

Experts widely view North Korea's military involvement in Ukraine as a lucrative move for Kim's regime. Beyond the combat experience gained by North Korean troops, the impoverished nation is believed to have received cash, oil, food and other essential supplies from Russia in exchange for weapons sales and troop deployment.

Perhaps most significantly, North Korea's relations with Russia have been strengthened to a level not seen since the Cold War.

This captured image from Ukrainian President Volodymyr Zelenskyy's social media shows a wounded North Korean prisoner of war. He was captured in the Kursk region of Russia on Jan. 12 during the war in Ukraine. Courtesy of Volodymyr Zelenskyy

Kim Young-hee, a non-resident fellow at the Dongguk University Institute of North Korean Studies in Seoul, said that North Korean millennials and Generation Z have now gained firsthand combat experience in Ukraine — an achievement she described as unparalleled.

"Through their time on the battlefield, they have learned how to enhance their combat skills," she said. "Although many soldiers have been wounded or killed, the North Korean regime is likely to view the benefits as outweighing these sacrifices."

Kim speculated that rather than receiving direct monetary compensation, North Korea's reward for its troop deployment would likely come in the form of technology transfers or other strategic know-how from Russia.

"Some believe North Korea is being paid in cash, which would then be used to develop nuclear weapons or other weapons of mass destruction. But I disagree," she said, emphasizing that direct financial transactions could pose technical challenges for Pyongyang. "For Kim Jong-un, acquiring advanced technology is more urgent than receiving cash."

Since March last year, Russia has reportedly supplied North Korea with more than one million barrels of oil, according to satellite imagery analysis by the U.K.-based research group Open Source Centre. BBC reported that this oil shipment — allegedly in exchange for North Korean weapons and troops — violates U.N. sanctions. Due to persistent sanctions and a struggling industrial infrastructure, North Korea faces chronic energy shortages. The Russian oil supply has helped alleviate this crisis.

According to BBC, oil is essential for North Korea's military operations, with diesel and petrol needed to transport missile launchers and mobilize troops. Additionally, Russia has reportedly agreed to provide North Korea with 600,000 to 700,000 tons of rice annually, which, if delivered, could help ease the country's severe food shortages.

However, it remains unclear whether food aid, oil shipments and potential technology transfers from Russia will allow Pyongyang to significantly advance its weapons systems after the war in Ukraine — just as South Korea achieved military modernization following its involvement in the Vietnam War.

The Brown Memorandum, signed between South Korea and the U.S. during the Vietnam War, outlined U.S. assistance in supplying South Korea with substantial military equipment to modernize its armed forces. This raises the question: Will Russia be both willing and able to play a similar role in North Korea once the war in Ukraine ends, just as the U.S. did for South Korea after Vietnam? It is a question that remains unanswered.

Russia's President Vladimir Putin and North Korean leader Kim Jong-un sign joint documents during a ceremony at the Kumsusan State Guest House in Pyongyang, North Korea. TASS-Yonhap

The war in Ukraine served as a testing ground for North Korean weaponry, but it also exposed serious flaws. Embarrassingly for Pyongyang, the war revealed the poor quality of its artillery shells and missiles. Ukrainian officials analyzed North Korean missiles fired during the conflict and concluded that about half veered off their programmed trajectories and exploded mid-air.

Despite these shortcomings, Park warned that South Korea should not underestimate North Korea's growing military threat. "Just as individuals learn from their mistakes, North Korea will have learned valuable lessons from the war in Ukraine — particularly how to improve its artillery and missile technology," he said.

Experts stress that one of the most concerning takeaways is North Korean troops' exposure to modern warfare. "Before the war, North Korean soldiers may have only heard about drones and their versatile uses in combat. But in Ukraine, they gained hands-on experience operating them," said Lee Ho-ryong, head of the Center for Security and Strategy at the Korea Institute for Defense Analyses.

North Korean troops also gained a reputation for their discipline and fearlessness on the battlefield. "According to Ukrainian soldiers, North Koreans were extremely loyal and, at times, frustratingly brave," Lee said. "A Ukrainian intelligence officer was even quoted as saying that one North Korean soldier was equivalent to five Russian soldiers — suggesting they are resilient, tough and unafraid of death, as seen in their suicidal attacks."

Lee noted that North Korean troops have played a crucial role in the war, which could become a key bargaining chip for Kim Jong-un in future negotiations with Russia. "Kim may argue that Russia gained a stronger position in ceasefire talks with the U.S. thanks to North Korean troops, who helped reclaim the Kursk region from Ukraine after six months of occupation," she said. Lee speculated that Kim would continue leveraging North Korea's military contributions to deepen ties with Russia even after the war.

Experts urge South Korea to closely monitor how North Korea's combat experience in Ukraine will shape its military capabilities. Park emphasized that such an effort requires bipartisan support.

He lamented that national security, like many other issues, has become politicized. South Korea had attempted to send a team of experts to study the war in Ukraine, but the plan was blocked by the National Assembly. "Some opposition lawmakers wrongly portrayed the team's mission as a precursor to troop deployment, which was not the case," he said.

Lee stressed the importance of international cooperation to counter potential Russian transfers of sensitive military technology to North Korea. She urged the South Korean government to closely track Pyongyang's evolving combat tactics — particularly its use of drones, which could become a greater threat in future conflicts.