Earlier this month, North Korean leader Kim Jong Un called Russian President Vladimir Putin his "closest comrade", and promised relations between the two countries would be soon raised to a new level.
This week, the Pentagon confirmed this was all but true — a total of about 10,000 North Korean troops are currently in Russia.
And the North Korean soldiers are not only on Russian soil, but a "small number" have already been deployed in Russia's Kursk region on the Ukrainian border, the Pentagon said.
Russia and North Korea have boosted their political and military alliance across the course of the two-and-a-half year conflict with Ukraine, but the deployment of Pyongyang's troops into combat against Kyiv's forces marks a significant escalation.
But what exactly does this mean?
Here's everything we know.
Where are the North Korean troops?
For months, North Korea has been providing Russia with short-range ballistic missiles, artillery shells, and other weapons, according to intelligence officials in the United States, South Korea, and Ukraine.
But now, North Korea has sent some 10,000 troops to Russia, the Pentagon said, more than tripling the previous estimate.
The Pentagon's announcement is the first US confirmation of a North Korean deployment in the region, where Ukrainian troops have been conducting a ground offensive since August and control approximately 500 square kilometres of Russian territory.
There are "indications that there's already a small number that are actually in the Kursk Oblast, with a couple thousand more that are either almost there or due to arrive imminently," Pentagon spokesman Major General Pat Ryder said of North Korean troops.
"We are concerned that they do intend to employ these forces in combat against the Ukrainians," Major General Ryder said.
Justin Hastings, a professor of International Relations at The University of Sydney, said the development marks the first time another country has formally sent actual troops of its own to fight in the war between Ukraine and Russia.
"Prior to this development, international involvement [in the war] has entirely been other countries sending military weapons and equipment, or receiving international volunteers," he said.
What role will these troops play?
What role the North Korean troops may play is unclear.
The Pentagon said initial indications are that Russia might field them in infantry roles.
"We remain concerned that Russia intends to use these soldiers in combat or to support combat operations against Ukrainian forces in Kursk," Pentagon spokesperson Major General Ryder told reporters.
The Center for Strategic and International Studies (CSIS) think tank said the number of North Korean forces involved "make this more than a symbolic effort".
"But the troops will likely be in support roles and constitute less than 1 per cent of Russia's forces," it said.
"Russia is desperate for additional manpower, and this is one element of Russia's effort to fill the ranks without a second mobilisation," it added, noting the presence could grow.
Professor Hastings said that initial reports that North Korea was sending a large percentage of special forces troops, which in some sense means that many may not be fighting on the front line.
"A lot of what they might send is people who can construct defensive lines, people who can build bridges, or [be] used for support, or engineer work" he said.
And due to the scale of the North Korean military, Professor Hastings said that 10,000 troops wasn't "a particularly large commitment".
He said that the North Korean troops may have also been initially placed in Russia to evaluate the success rate of North Korean missiles that were used, and the quality of their ammunition to improve it in the future.
And for the regular troops?
"We don't really know. They could go to the front line, but 10,000 troops on the front line won't last very long, especially if they haven't been trained for very long," he said.
"If you want actual combat troops for the front line, you need a fair number of people. And so I assume that is why they sent that number."
Professor Hastings emphasised that the operation would be difficult without extensive training and integration into the Russian military.
"I can imagine they [troops] would be put into regular combat roles, but without integration into the Russian military and without training, I'm not sure how long they are going to last there."
Wait, how does this even work?
As North Korean soldiers arrive in Russia, you can imagine there would be a few teething problems.
Last week, CNN reported that Russian soldiers were heard via leaked audio intercepts questioning how North Korean soldiers will be commanded.
On Tuesday, South Korean politicians said the military in Russia was trying to teach military terminology to the North Korean soldiers, briefed by the country's spy agency.
Moscow was also continuing to provide technical support for North Korea's attempts to field a fleet of spy satellites, the politicians said.
Professor Hastings said that to his understanding, the North Korean soldiers had been given Russian uniforms, weapons, and fake identities as Russian soldiers, and have been taught a few lines of Russian in terms of commands.
"Like all things Russia does, in terms of training, clearly no thought has been given to how to actually integrate them into units, or even how to control them," he said.
Is this fair game?
To put it simply, it's a bit of a grey area.
Russia's envoy to the United Nations on Wednesday questioned why its allies like North Korea could not help Moscow in its war against Ukraine given Western countries claim the right to help Kyiv.
Vassily Nebenzia faced a blunt argument at a Security Council meeting from the US, Britain, South Korea, Ukraine and others, who all accused Russia of violating UN resolutions and the founding UN Charter with the deployment of troops from North Korea.
"Supporting an act of aggression, which completely violates the principles of the UN Charter, is illegal," South Korea's UN ambassador Joonkook Hwang said.
"Any activities that are entailed with the DPRK's dispatch of troops to Russia are clear violations of multiple UN Security Council Resolutions."
Mr Nebenzia said Russia's military interaction with North Korea does not violate international law.
"I would like to underscore that the Russian interaction with [North Korea] in the military and other areas is in line with international law and is not a violation of it," Mr Nebenzia said.
Professor Hastings explained that the extent that the North Korean soldiers are employed outside of North Korea is a violation of sanction.
"It is illegal to employ North Korea outside of North Korea, and it is illegal to give North Korea [troops] weapons and equip them, even with small arms," he said.
"And so the extent Russia is equipping them is illegal under UN sanctions. It is also illegal under UN sanction to buy ammo or any kind of weapons from North Korea, so Russia using North Korean missiles and ammunition are all illegal under UN sanctions," he said.
"The physical act of North Korea sending troops to a war zone, if they did nothing else, you can maybe argue isn't violating sanctions, but literally everything they do to support that is [violating UN sanctions]."
But the US has said any North Korean troops fighting in the war would be "fair game" for Ukrainian attacks and that Washington would not impose any fresh limits on Ukraine's use of US weapons if North Korea entered the fight.
"They're fair targets and the Ukrainian military will defend themselves against North Korean soldiers the same way they're defending themselves against Russian soldiers," said White House spokesperson John Kirby.
What is North Korea getting out of this?
Russia and North Korea have boosted their political and military alliance in the course of the Ukraine conflict.
Both are under sanctions — Pyongyang for its nuclear weapons program, and Moscow for its war against Kyiv.
Experts have said that in return for these forces, North Korea is likely aiming to acquire military technology, ranging from surveillance satellites to submarines, plus possible security guarantees from Moscow.
Professor Hastings said he believes North Korea strategically "gets an ally outside of China".
"It gives them a lot more leeway to operate in the world, than they would if China was there only ally," he said.
"In that sense, this is what North Korea has been hoping for all along."
Professor Hastings added that North Korea may also be motivated by new missile technology, or maybe money or oil, but the bottom line was that they were going to make a profit.
"Russia is paying for pretty much everything associated with equipping and training these troops," he said.
"North Korea is going to make a profit off this, regardless."
Deployment could lengthen, broaden Ukraine war, officials warn
North Korea's deployment to Russia to aid its war against Ukraine has the potential to lengthen the conflict and draw in additional actors, US Defense Secretary Lloyd Austin said.
After talks with his South Korean counterpart at the Pentagon, Kim Yong-hyun, Mr Austin called the deployment a "dangerous and destabilising escalation".
"It does have the potential of lengthening the conflict or broadening the conflict," Mr Austin told reporters, standing alongside Kim. "It could encourage others to take action, different kinds of action … There are a number of things that could happen."
If North Korea aids Russia's war, North Korean troops can expect to be targeted by Ukrainian troops using weapons provided by the US and its allies, and some will likely die on the battlefield, he added.
"If they are fighting alongside of Russian soldiers, they are co-belligerents, and we have every reason to believe that … they will be killed and wounded as a result of that," Mr Austin said.
Ukraine's President Volodymyr Zelenskyy said after talks with South Korean President Yoon Suk Yeol on Tuesday that the North Korean moves were sending the war into a new phase.
"This war is becoming internationalised, extending beyond two countries," Mr Zelenskyy said on X.
Canadian Prime Minister Justin Trudeau added that the deployment of North Korean troops will likely escalate the war, the South Korean president's office said on Wednesday after a phone call between the leaders.
The war will leave a greater impact on the security environment of Europe and the Indo-Pacific, Mr Trudeau said, according to Mr Yoon's office.
It comes as North Korea conducted what appeared to be its longest ever intercontinental ballistic missile test on Thursday.
ABC/Reuters
