Thousands of troops, millions of shells

The Reuters investigation shows the extent of Russia’s reliance upon North Korean shells on the battlefield, which helped it pursue a war of attrition that Ukraine has struggled to match. At times over the past year, the vast majority of shells fired by some Russian units were from North Korea, Reuters found.

An analysis of sea and land shipments by the Open Source Centre in conjunction with Reuters was confirmed by Russian artillery reports intercepted by Kyiv, satellite imagery and verified social media videos, as well as three senior Ukrainian government and military sources.

North Korea has also dispatched ballistic missiles as well as long-range artillery and multiple-launch rocket systems. Its deliveries represent the most significant direct military aid to Russia’s war effort, which has also benefited from Iranian long-range drone technology and close economic support from China.

The Open Source Centre, or OSC, an independent UK-based research organization focused on security, tracked 64 shipments over 20 months carrying nearly 16,000 containers and millions of artillery rounds for use against Ukraine, including a shipment as recent as March 17.

The military partnership between North Korea and Russia came to light in 2023. It took on new importance in recent weeks, when North Korean troops, weapons systems and ammunition bolstered Russian firepower to evict the remnants of Ukraine’s incursion in Russia’s Kursk region just as the Trump administration was pulling support for Ukraine.

Ukrainian officials, including the military intelligence chief, have said North Korea is supplying half the munitions Russia needs at the front — a quantity consistent with the findings by both OSC and Reuters. One expert in the Ukrainian military told Reuters that the North Korean contribution was as high as 70%, and Reuters found that at times Russian artillery units were almost wholly reliant upon North Korean munitions.

“North Korea’s contribution has been strategically vital,” said Hugh Griffiths, who from 2014 to 2019 was coordinator of the U.N. panel of experts that monitored sanctions on North Korea. “Without Chairman Kim Jong Un’s support, President Vladimir Putin wouldn’t really be able to prosecute his war in Ukraine.”

Though Western military support for Ukraine has kept it in the war since Russia’s full-scale invasion in February 2022, including a Czech initiative to supply 1.6 million rounds of ammunition, that aid has been inconsistent and of late appears increasingly uncertain.

At no point has any Ukrainian ally offered up its own soldiers to fight. 

By January, around 4,000 North Korean soldiers had been killed or wounded fighting against Ukrainian forces since they first arrived in Kursk in late autumn, according to a South Korean security source. North Korea sent 3,000 more men by mid-February – and the reinforcements were better prepared, said Oleh Shyriaiev, commander of Ukraine’s 225th Separate Assault Regiment, which has been fighting in Kursk.

“They adapted to modern combat conditions,” Shyriaiev recalled.

Ukraine’s military intelligence chief, Kyrylo Budanov, said in late February that North Korea also supplied 120 long-range self-propelled artillery systems and 120 multiple launch rocket systems to Russia beginning in late 2024, including some filmed by Ukrainian drones in Kursk.

Russia’s recent victories in Kursk come at a crucial time. U.S. President Donald Trump says he wants a quick end to the war, and Ukraine had hoped that holding Russian territory would strengthen its hand in negotiations.

But now only a tiny pocket of Kursk remains under Ukrainian control.

North Korea’s delegations at the United Nations in New York and Geneva, and its embassy in London, did not respond to detailed questions about Reuters’ findings, nor did Russia’s Defense Ministry or South Korea’s National Intelligence Service and Ministry of National Defense.

Shared border, shared history

Russia and North Korea share a short border and a history.

Kim Il Sung, who fought in the Soviet Red Army during the Second World War, became North Korea’s first leader and received Soviet support during the Korean War and beyond. He ruled until his death in 1994, starting the dynasty that remains in power.

In 1959, the countries commissioned a “Friendship Bridge” for trains crossing the Tumen River, which marks the border they share, a stone’s throw from the Chinese frontier. Relations cooled after the Soviet Union’s collapse.

The two countries’ ties warmed again as Russia found itself increasingly politically and economically isolated over the war in Ukraine.

Ukraine’s first counteroffensive in late 2022 forced Russia into retreat from vast swathes of Ukrainian land. Russia spent the next six months digging trenches, laying mines and erecting defensive structures. That combination stalled Ukraine’s second counteroffensive in summer 2023, and the war became one of attrition in which both sides have tried to outgun and outkill each other.

Since the war’s beginning, Russia has had more soldiers and firepower than Ukraine, in addition to its enormous military industrial capacity. Putin has not backed down in his goals, claiming a vast portion of Ukraine’s internationally recognized territory is, in fact, Russia.

But by 2023, in a throwback to the trench warfare of the First World War, artillery and mortar fire became the keys to holding territory and prising the enemy from defensive positions. Whoever had the most shells would have a major advantage.

At that point, military experts estimated that both Russia and Ukraine were at times firing 10,000 artillery rounds a day, exhausting their supplies.

Ukraine’s allies in Europe, the United States and Asia continued to scour the world and their own stocks for shells, helping a much smaller army compete with Russia.

Russia’s Defense Minister Sergei Shoigu travelled to Pyongyang in July 2023 to celebrate the 70th anniversary of the Korean War armistice. He and Kim discussed closer military cooperation.

Already in September 2023, ships started carrying hundreds of containers from the North Korean port of Rajin to the eastern Russian ports of Dunai and Vostochny, according to the OSC, which monitors daily satellite images of the ships.

The United States has said the containers held armaments that were loaded onto trains for transport thousands of kilometers away to weapons depots in western Russia. At the end of 2023, a Ukrainian government assessment seen by Reuters found that the Cold War-era Friendship Bridge was being used, along with much bigger deliveries by ship.

First reported by the London-based Royal United Services Institute think tank in October 2023, the shipments expanded rapidly over the following months and the OSC has tracked them since their inception. Deliveries peaked in January 2024, with seven shipments crossing into Russia, before dropping to a monthly average of around three through March 2025.

The North Korean munitions were introduced methodically. The Russian military compiles “firing tables” for artillery units based on testing performed at the Luzhsky Artillery Range, the expert in the Ukrainian military told Reuters, speaking on condition of anonymity to discuss sensitive matters.

Reuters reviewed four firing tables, including a 60-page technical document with guidelines for using the North Korean shells with Russia’s M-46, a towed field gun first developed in Josef Stalin’s Soviet Union. One section, for example, warns against keeping a particular North Korean munition in a hot barrel for more than 3 minutes. It also offers specific firing angles for given distances.

With testing and specifications complete, the North Korean shells bombarded the Ukrainian frontlines. Reuters reviewed nine Russian military documents containing tables in which artillery units reported up the chain of command about munitions usage and stocks.

Six of the nine reports, which are daily snapshots of weapons usage, showed North Korean munitions were prevalent. Two from this year showed units using 100% North Korean munitions on one day and 75% on another. Last summer, a unit on the southeastern Zaporizhzhia front reported nearly 50% of the shells fired by its D-20 howitzers were North Korean 152 mm shells, while 100% of its 122 mm rockets were North Korean. Two of the reports describe extensive North Korean stocks, without specifying percentages. Three reports don’t specify North Korean ordnance.

“Without help from the DPRK, the Russian army shelling of Ukrainian defensive positions would have been cut in half,” Ukraine’s military intelligence directorate, known as GUR, wrote in response to questions from Reuters, using the acronym for North Korea. 

It was around autumn 2023 that Ukraine saw its own supplies of artillery shells dwindle, forcing batteries across the frontlines to limit fire.

Republicans in Washington in late 2023 suspended a $61 billion military aid package for Ukraine. The knock-on effect was quickly felt despite Europe’s efforts to make up shortfalls. By April 2024, Ukrainian President Volodymyr Zelenskiy told PBS in an interview that for every Ukrainian shell, Russia was firing 10 back.

An increasing portion of those were North Korean.

In all, OSC found that the same four ships – all of them under international sanctions – have made a total of 64 trips from North Korea to Russia, loading containers in Rajin and offloading them at the two Russian ports.

A U.N. report as well as a 16-page Ukrainian government document seen by Reuters also lists the four ships making North Korean deliveries to its ally. The pace has remained steady for the past year, including four deliveries in February 2025 and two in March 2025, according to satellite data gathered by OSC.

The group counted containers being loaded onto each vessel using satellite imagery and detailed modelling. It has observed hundreds of containers of similar size and coloring arriving by rail at arms depots in western Russia.

The Ukrainian government document identifies railway deliveries to Russian military units at six locations between April 16 and May 9, 2024. It details hundreds of rail platforms and rail cars. Reuters and OSC identified those and another three depots where satellite imagery shows contours consistent with storage areas.

It’s not possible to verify the ammunition inside each shipping container, but OSC estimated what it called a conservative range of 4-6 million artillery rounds alone, based on Ukraine’s assessment of their prevalence and probable packing patterns. Either way, North Korean deliveries would be a sizable addition to Russia’s production, estimated by Ukrainian and Western officials at 2-2.3 million artillery shells in 2024. U.S. Army General Christopher Cavoli, the top U.S. general in Europe, told American lawmakers on April 3 that he anticipated Russia’s yearly production to be 3 million artillery shells, without specifying when that could happen.

GUR told Reuters that North Korea had provided 4 million artillery shells alone since the middle of 2023, more than three-quarters of them the 122mm and 152mm caliber rounds that are at the heart of Russia’s ground weaponry. GUR said North Korea provided mortar rounds as well, but did not include them in that figure.

Konrad Muzyka, a military analyst who runs Rochan Consulting, an independent security consultancy based in Poland, said Russia maintained an intensity of assaults beginning in late 2023 thanks to North Korea’s help. 

“It allowed the Russians to maintain an offensive posture and constant pressure on Ukrainian forces throughout most of 2024 into 2025,” he said.

One of the main destinations for North Korean armaments was Tikhoretsk, a supply hub for Russia’s military fighting in Ukraine about 100 kilometers south of Rostov-on-Don.

Expansion started at the facility in late summer 2023 as North Korean ammunition was about to arrive in force, according to a Reuters analysis of high-definition satellite imagery. Just over a year later, on September 21, 2024, the facility was bombed in a strike claimed by the Ukrainian military.

OSC estimated that the strike destroyed about 90% of the facility’s capacity, including a major delivery from North Korea just days before.

Kursk

With superior troop numbers and newly replenished ammunition, Russia made slow but steady territorial gains in mid-2024 by concentrating in eastern Ukraine. 

That left an opening that Ukraine exploited – to the surprise of both its own allies and Russia. In August 2024, Ukrainian forces launched an audacious incursion into Russia’s Kursk region, taking hundreds of square kilometers.

With the addition of the North Korean troops in early November, Ukrainians estimated a force of at least 60,000 soldiers in all arrayed against them in Kursk. Reuters could not verify the troop numbers. A few weeks later Ukrainian military intelligence intercepted two radio messages involving the North Korean troops and shared them with Reuters. 

A North Korean soldier who defected to South Korea listened to the shared recordings at the request of Reuters, to better understand the circumstances and military jargon scattered throughout the conversations.

In the longer of the two, intercepted on December 9, what appears to be a commander and subordinate discuss how soldiers could safely collect food. The key was to avoid detection.

“Make sure they never gather together,” said the commander, who is not identified. It was not clear where in Kursk either conversation took place.

They also speak about a wounded soldier and his military identification, suggesting that language barriers made it difficult for them to discern whether he was Russian or Ukrainian.

“Currently, the Russian UAV (drone) platoon will evacuate and then interrogate him. Over,” the soldier tells his superior.

On January 4, Zelenskiy said that Russian and North Korean troops had suffered heavy casualties in Kursk and a week later he announced that two North Korean soldiers had been captured. 

Reuters reviewed a Ukrainian intelligence document detailing their questioning.

Both prisoners initially exhibited “suicidal tendencies” upon capture, the document said. The Ukrainian military has described how at least one North Korean soldier blew himself up to avoid being taken prisoner.

The intelligence document identified one of the men as a senior soldier who had served since May 2021. The second was a junior sergeant from Pyongyang who had served since August 2016. Reuters is not identifying the men because they and their families could face retribution in North Korea.

The two men told interrogators they sailed from North Korea to Russia with around 100 other soldiers, arriving in Russia in November 2024 and undergoing exercises at training grounds.

They said they were only told they were going to Russia for exercises and that they left their military registration documents in North Korea.

After arriving in Russia, they were given a Russian-style “military card” written in Russian Cyrillic with no photo.

The senior soldier had a fractured left leg and the junior sergeant took a gunshot wound to the face, requiring his lower jaw to be removed. His interrogation was conducted in writing. They were captured on January 3 during their first battle, the document said. 

The sergeant said the North Korean soldiers despised the Russians because they refused to go on assault operations like North Korean soldiers did.

Shyriaiev, the Ukrainian officer who fought against North Koreans in Kursk, agreed with that assessment.

“They continue to be used as assault units that advance, storm. And behind them are units of the Russian Federation, which consolidate and hold positions. That is, Koreans are used as assault troops.”

Battle hardened

North Korea’s involvement in Ukraine has alarmed not only European capitals but also South Korea and its allies in Asia, who fear that lessons learned from war could be unleashed on them one day.

Cavoli, the U.S. commander, told lawmakers that in return for supplies of shells, missiles and weapons systems, “Russia is almost certainly transferring missile technology to Pyongyang.” Reuters could not verify his statement. He added that in the last year, North Korea had sent more than 13,000 containers of supplies to Russia.

Both countries deny arms transfers and do not publicly acknowledge the deployment of North Korean troops in Kursk. When challenged about the deployment, Russia has questioned why allies could not help its war effort given Western countries’ support for Ukraine.

North Korea has one of the world’s largest armies and has been stockpiling massive amounts of ammunition for decades in preparation for a potential war with South Korea, and while some of it is of questionable quality, much of it still works and gave Russia crucial superiority, said Yang Uk, a military expert at Seoul’s Asan Institute for Policy Studies.

“Since the Russian way of war is based upon fire superiority, it takes tons of ammunition. And the only country that can provide that kind of volume, besides Russia, is North Korea,” he said.

Russia, meanwhile, has depleted its stockpiles since the war’s beginning. Using North Korea’s shells could let Russia start stockpiling its new production of higher quality munitions, said Muzyka, the military analyst.

But North Korea has reaped rewards valued by any military commander. Elite army units have leapt from exercises at home into real-life combat. They have proven themselves capable of adapting.

Just as important has been North Korea’s ability to solve problems with the accuracy and consistency of its artillery munitions and ballistic missiles in wartime conditions, Ukrainian officials have said.

Russia began striking Ukraine with North Korean ballistic missiles at the end of 2023. Armed with warheads up to one ton – larger than the Russian equivalent – they initially proved to be inaccurate and unreliable, according to Ukrainian military analysis.

A Reuters journalist who arrived shortly after one fell in central Kharkiv on January 2, 2024, said the aftermath was unlike any he’d seen before. The missile debris was different, with intact chunks of engine and larger fragments made of a metal that seemed heavier and of lesser quality than others he’d viewed.

Ukraine and the United Nations later confirmed the weapon was from North Korea.

A readout from Ukraine’s military came two months later: In weeks of North Korean ballistic missile bombings, they had only hit two military targets out of 24 strikes.

By the start of 2025, North Korea had supplied Russia with 148 KN-23 and KN-24 ballistic missiles, GUR told Reuters.

In February, two senior Ukrainian sources told Reuters that newer North Korean missiles had become significantly more precise since their first use in Ukraine more than a year before.

One of the sources, a senior military official, said the latest versions were accurate to within 50-100 meters of their target. Budanov, the head of Ukrainian military intelligence, later confirmed the improved accuracy in an interview with South Korean media.

Over the course of 2024 and into this year, drones have taken ascendancy over artillery on the battlefields of Ukraine. Guided remotely by pilots wearing electronic visors, thousands of the aircraft buzz over the frontline each day, posing a mortal danger to individual soldiers and heavy machinery.

But North Korean soldiers and munitions continue to play a crucial role, as the recent sea shipments attest. And there may soon be an easier way to move men and equipment between the countries. 

Russia’s ambassador to Pyongyang recently announced a new road bridge over the Tumen River to be built near the decades-old Friendship Bridge. He said there were no concerns about renewed contacts between Russia and the United States, describing the alliance with Pyongyang as “a fraternal friendship between the Korean and Russian peoples, which were cemented by the blood that was spilled together.”