SEOUL, South Korea — North Korea’s entry into Russia’s war against Ukraine is a major escalation in the grinding conflict, but Moscow may find it’s more trouble than it’s worth.

North Korean leader Kim Jong Un has sent thousands of soldiers to Russia, the U.S. and others say, stepping up his assistance against Ukraine as he and Russian President Vladimir Putin strengthen security ties.

With victory still elusive as the war nears the end of its third year, Putin welcomes more help from North Korea, which has already been providing weapons, experts say. But the inexperience of the North Korean soldiers as well as the language barrier between them and their Russian counterparts are likely to minimize their impact on the battlefield, military analysts told NBC News.

“The average Russian soldier is going to say, what are they doing here? I’m having to hold their hand. I’m tripping over their bodies,” said Sydney Seiler, the U.S. national intelligence officer for North Korea from 2020 to 2023.

The State Department said Tuesday that most of the more than 10,000 North Korean soldiers sent to Russia had started fighting in the Russian region of Kursk, where Ukrainian forces launched an offensive in August.

South Korea’s National Intelligence Service also said this week that North Korean soldiers deployed to Russia had started engaging in combat.

Putin did not deny the presence of North Korean troops in Russia when asked by NBC News last month, while North Korea has not confirmed it but said it would be in line with international law.

The North Korean troops could give a boost to Russia’s depleted forces as they try to retake control of Kursk, which is the first Russian territory to be occupied by a foreign military since World War II.

“Every North Korean soldier that can dig a latrine, guard an intersection, seize and hold a building allows one more Russian soldier to go to the front line,” said Seiler, who is now the Korea chair at the Center for Strategic and International Studies, a think tank in Washington.

North Korea-Russia cooperation was the issue “addressed most in-depth” at a meeting on Friday between President Joe Biden and the leaders of two key U.S. allies at risk from Pyongyang, South Korean President Yoon Suk Yeol and Japanese Prime Minister Shigeru Ishiba, a senior administration official said.

“There was tremendous convergence on just how destabilizing this growing nexus between Moscow and Pyongyang is for the region,” the official said of the meeting, which took place on the sidelines of the Asia-Pacific Economic Cooperation forum in Lima, Peru.

The U.S. and others say that Kim, who on Monday ratified a mutual defense pact that he and Putin signed in June, was already supplying Russia with millions of artillery rounds, possibly in exchange for Russian technical assistance with his nuclear and ballistic missile programs. Both Pyongyang and Moscow deny any arms transfers.

The North Korean troops, some of whom South Korea says are part of Pyongyang’s special operations force, could now be used to form combat units or operate that artillery, analysts say.

They are unlikely to make a meaningful difference on the front lines, however. Though North Korea has the world’s fourth-largest army, the deployment in Kursk is the first major combat its soldiers have seen since the 1950-53 Korean War.

“Kim Jong Un is selling North Korean soldiers as cannon fodder mercenaries,” South Korean Defense Minister Kim Yong-hyun said last month.

It’s an entirely new environment for the North Korean soldiers, who live in one of the most isolated and repressive countries in the world. The Pentagon said last week that it was unable to confirm reports that North Korean troops unused to unfettered internet access were spending much of their time consuming online pornography, Politico reported.

There is also the risk that North Korean soldiers could defect or be taken as prisoners of war, either of which could prove embarrassing for Kim and Putin.

Even if that doesn’t happen, the North Koreans could end up being less help than hindrance, Seiler said.

“There is a lot of skepticism and questioning now that are these troops even viable?” he said.

Mismatched skills and missing camaraderie

The Russians’ frustration was on display last month in what Ukrainian military intelligence said were intercepted audio messages between members of a Russian unit in Kursk.

In the messages, Russian soldiers appear to complain about their North Korean counterparts, referred to as the “K Battalion,” with one soldier saying he doesn’t know “what the f— to do with them.”

NBC News has not independently authenticated the audio, and the Russian Ministry of Defense has not publicly commented on it.

There is also the matter of the language barrier, which will be “a significant hurdle,” said John Hardie, deputy director of the Russia program at the Foundation for Defense of Democracies, a Washington-based think tank.

Communication difficulties between Russian and North Korean soldiers will “complicate command and control, especially if Russia attempts to integrate the North Koreans into lower echelons,” he said.

The Russian military is teaching the North Korean soldiers about 100 key military terms, but “North Koreans are having a difficult time learning Russian,” South Korean lawmakers Lee Sung-kwon and Park Sun-won said last month.

While translators and some basic vocabulary may help, combat operations “require constant and specific communications to be really successful, not just some senior officer pointing in a direction and telling the North Koreans to attack there,” said Bruce Bennett, an adjunct senior researcher at the California-based nonprofit think tank Rand Corp.

Communication is not the only issue that could keep Russian and North Korean forces from fighting together effectively. North Korean soldiers’ inexperience could be another point of friction and a major factor in how they are deployed.

“North Korean troops will likely have had limited exposure to some of the capabilities and tactics, techniques and procedures that have evolved during the war in Ukraine,” Hardie said. “There will be a lot of learning on the job.”

Given these constraints, Bennett said, the Russian military might revive a strategy it used in the Cold War: forming what is known as an operational maneuver group (OMG), which goes farther across enemy lines than traditional units and includes elite soldiers who can cripple the enemy’s defenses from inside.

“The Russians may be thinking of using part of the North Korean force to carry out massed attacks, hoping to overwhelm Ukraine’s defenders,” Bennett said. The rest, he said, could become part of an OMG that goes deep into Ukrainian-held territory.

For Putin, this could provide a “strategic breakthrough” against Ukraine’s defenses and create conditions to end the war with a Russian “victory,” he said.

Though the North Korean troops are unlikely to make much difference in Putin’s overall strategy in the Ukraine war, they could help him prolong it, said Edward Howell, a North Korea expert at Chatham House, a London-based think tank.

Their presence could also bring continued goodwill from the Russian president.

“Even if the Ukraine war were to end, the relationship between North Korea and Russia now seems to have reached new heights,” Howell said.

Stella Kim reported from Seoul, South Korea, and Mithil Aggarwal from Hong Kong.