There is no longer much doubt there are North Korean troops training in far eastern Russia.
Western intelligence services predict that some of these troops will soon be fighting in Kursk.
If they end up doing so, it could backfire badly on the Russians. It can also destabilize the Kim regime in Pyongyang.
It is important to keep in mind that Kursk is Russian territory. It was the Ukrainians who invaded Kursk. From what we understand, the Ukrainians are losing a lot of men and equipment and are systematically, if slowly, being pushed out of Kursk-area villages. Three thousand or even ten thousand North Koreans are not likely to make any battlefield difference. A Russian combat brigade is about 8,000 foot soldiers, so a North Korean contribution would be about one brigade on the battlefield.
The North Koreans observed so far are foot soldiers. They do not appear to have armor (tanks, infantry fighting vehicles, armored personnel carriers) or artillery. They also have only minimal training on Russian tactics, and most of them do not speak the Russian language.
If the North Koreans actually do fight on Russian territory they are not mercenaries, as some news reports suggest. The collective west has supplied some 13,000 mercenaries to Ukraine, and an unknown number of uniformed troops who work as advisors and as specialists operating air defenses and critical communications and command and control nodes.
The Russian Duma has just ratified a defense agreement with North Korea that provides for mutual self help in case either is attacked. Ukraine's incursion in Kursk amounts to a land invasion of Russian territory, and thus it would trigger the mutual defense agreement between the DPRK and Russia.
No one knows much about North Korea's military. It has not fought in a land battle of any consequence for decades, since the armistice agreement ending the Korean fighting in 1953. By any measure it is inexperienced and mostly lacks modern equipment.
North Korea has mainly obsolete tanks, but these are not apparently in Russia. It does have plenty of artillery, but its artillery systems also have not been seen in Russia. Not much is known about the DPRK army's communications and command and control, but it is likely quite old fashioned. How it could be linked to much more modern Russian systems is an open question.
The Ukrainians are playing up the possibility of North Korean troops in Kursk for one simple reason: Zelensky and Budanov, his military security chief, want the west to send troops to Ukraine to save them from defeat. They see the arrival of North Korean troops as a strong argument for NATO, or components of NATO, to send land forces to Ukraine.
There is no consensus in NATO to bring Ukraine into the alliance or to send troops openly to Ukraine. It is true that the French are in favor of both, but the Germans and Poles are not, and neither are many others. But, like the Iraq war, the failing US administration, the British and French, may try and put together a Coalition of the Willing. To do this they would need to convince some reluctant partners to support such an enterprise. Some will not, most prominently the Germans and the Poles.
A Coalition of the Willing would need bases in Poland to run in troops and supplies. The Poles do not want to get hit by Russian missiles and glide bombs, so despite bravado talk coming from Warsaw, the chance for Poland's active support is near zero.
There is no doubt that Vladimir Putin is taunting the United States with the threat of North Korean soldiers fighting in Ukraine. Surely Putin must also know that running operations by North Korean troops would be a logistical and operational burden. It might give the Ukrainians an opportunity to kill many North Korean soldiers, damaging instead of supporting the new North Korea-Russia alliance. Likewise a bad result and many casualties would unsettle and destabilize the Kim regime, a family-led brutal dictatorship that has no practical way to know just how secure it really is from its own people.
Meanwhile the Ukrainians have little to fear from the use of North Korean troops. Managing them would be a mess for the Russians, and could hobble instead of helping Russian attempts to reclaim the Kursk territories. Surely Kiev knows this, but it remains hopeful help will come from some NATO countries to bail them out in a war they are losing, and that North Korean soldiers would be their ticket out of disaster.
This entire DPRK scenario is an American spook media op. Russia does not need a brigade of DPRK troops. The issues around communication and coordination are insurmountable outside of a catastrophe. In the event of a catastrophe, we'd see Chinese troops, not DPRK.
More likely, this is the US Security State laying building a box for Trump. The two areas Trump tried to deviate from the American regime consensus was 1) Russia and 2) DPRK. The Security State is connecting these two topics together, thereby preventing Trump from managing either.
Lastly, nothing will "destabilize" DPRK. The Chinese and Russians will ensure the state is empowered to survive whatever the Americans throw at it. Everything is different now.
Stephen, you write, "There is no longer much doubt there are North Korean troops training in far eastern Russia."
I am wondering if you could share how you reached this assessment, one that eschews probabilities for the rhetorical redoubt of certainty.
As you strongly imply, Russia has every right to accept military assistance or personnel from countries with which they have a mutual assistance agreement, especially since their territory was invaded. But Ukraine insists that North Korean troops will enter Ukraine any day, not just assist in Kursk, while US officials call it a "concerning probability".
Still, if your sources on DPRK troops sent West are the U.S. and Ukraine, you are basing your assumptions on demonstrated liars, who also present zero evidence.
OTOH, you are correct that in the numbers people are talking about, there is no military significance to an added 3000-5000 KPA soldiers. If anything, they would present logistical difficulties that would hinder Russia's military goals.
For my money, this is a propaganda game. Its implication is racist (not that you are racist, but those who invented this stratagem are counting on racism), as the Pentagon/CIA/Kyiv hope to conjure up visions of Communistic Asian hordes invading "white" Europe, necessitating a response from the "civilized" countries.