[Goose]

I don't see how individual North Korean soldiers would be spread out amongst Russian troops -- too many language (and probably cultural) differences.   It makes sense for them to fight as a unit or units.

In may ways having them fight as a unit "makes sense". However, from a Russian point of view it has several important downsides. As a single unit the Korean leadership may be unwilling to fight where and how Russia wants them to. They would have their own agenda and military philosophy. As a unit would have the ability to enforce it and act on their own. That isn't at all "the Russian way". The two groups also might not fully trust each other. Consider the row that was created when the US military refused to allow their sub-units to be assigned willy-nilly to reinforce existing French and British formations. There is lots of historical precedent for severe problems in using "allied" troops, especially when one ally is dominant in the partnership. The British willingness "to fight to the last Australian" is a good example of that, where both sides spoke the same language (mostly). 

While assigning Korean troops to Russian formations may seem a bit strange, that is exactly what the KATUSA program did for the US Army in the Korean war. While couched as a "liaison" program it was in reality an early-on attempt to use Korean manpower to make up for a lack of US manpower. Many US Army squads had two KATUSA troops to make up the numbers. It didn't work real well, but then not much did in the early days of the Korean war. Later on in the war and after the war it actually did.

For North Korea, this gives the first chance for these troops to face actual battle conditions.  No matter how well trained they are, this is an important step.  If N.K. is anticipating fighting their own battles in the next decade, this will be important for them.

Since N.K. and Russia recently signed a "defensive" mutual support treaty (sounds a bit like NATO, except for the matter that one of them is doing the invasion), this shouldn't be surprising.

The experience may be useful, but I suspect most of those Koreans won't be coming back. IMO the most important benefit seen by the North Korean leadership is the access to Russian technology and advanced weapons in return for the troops. I suspect the North will be disappointed but by then it will be too late to complain about Russia not living up to the deal. I suspect the North has extracted a promise from Russia to give them the design and know-how to build a fusion device. The North wants it and avoiding the uncertainties and delays inherent in doing it yourself is very valuable. North Korea may also have problems testing an H bomb. Using a Russian design might obviate the need to do so.

[Goose]

I don't see how individual North Korean soldiers would be spread out amongst Russian troops -- too many language (and probably cultural) differences.   It makes sense for them to fight as a unit or units.

In may ways having them fight as a unit "makes sense". However, from a Russian point of view it has several important downsides. As a single unit the Korean leadership may be unwilling to fight where and how Russia wants them to. They would have their own agenda and military philosophy. As a unit would have the ability to enforce it and act on their own. That isn't at all "the Russian way". The two groups also might not fully trust each other. Consider the row that was created when the US military refused to allow their sub-units to be assigned willy-nilly to reinforce existing French and British formations. There is lots of historical precedent for severe problems in using "allied" troops, especially when one ally is dominant in the partnership. The British willingness "to fight to the last Australian" is a good example of that, where both sides spoke the same language (mostly). 

While assigning Korean troops to Russian formations may seem a bit strange, that is exactly what the KATUSA program did for the US Army in the Korean war. While couched as a "liaison" program it was in reality an early-on attempt to use Korean manpower to make up for a lack of US manpower. Many US Army squads had two KATUSA troops to make up the numbers. It didn't work real well, but then not much did in the early days of the Korean war. Later on in the war and after the war it actually did.

For North Korea, this gives the first chance for these troops to face actual battle conditions.  No matter how well trained they are, this is an important step.  If N.K. is anticipating fighting their own battles in the next decade, this will be important for them.

Since N.K. and Russia recently signed a "defensive" mutual support treaty (sounds a bit like NATO, except for the matter that one of them is doing the invasion), this shouldn't be surprising.

The experience may be useful, but I suspect most of those Koreans won't be coming back. IMO the most important benefit seen by the North Korean leadership is the access to Russian technology and advanced weapons in return for the troops. I suspect the North will be disappointed but by then it will be too late to complain about Russia not living up to the deal. I suspect the North has extracted a promise from Russia to give them the design and know-how to build a fusion device. The North wants it and avoiding the uncertainties and delays inherent in doing it yourself is very valuable. North Korea may also have problems testing an H bomb. Using a Russian design might obviate the need to do so.