Russia's allies are now sending troops to help Russia in Ukraine, does that mean that Ukraine's allies can now finally send troops to help Ukraine?
No, it doesn't mean that.
No Western country would allow its troops to fight under the same conditions it expects Ukraine to fight, with an almost complete lack of protection.
Before sending ground troops, NATO countries would need to achieve air superiority. In other words, they would need to flatten every Russian airbase, from the occupied territories in Ukraine to the far east of Moscow.
The same applies to Russian air defense and missile artillery forces—everything that could pose a threat to their soldiers would need to be eliminated.
We saw the perfect execution of this strategy in two wars: the air war over Kosovo (1999) and Operation Desert Storm (1991). Not a single boot touched enemy territory until it was reasonably safe to do so.
A demonstration of Western airpower: the so-called “Highway of Death” during Operation Desert Storm (Picture: US Department of Defense)
Of course, pursuing such a strategy would require almost full NATO involvement in the war. This is a very different and much higher level of engagement than sending a few thousand soldiers to the meat grinder like North Korea does.
No NATO country would be willing to sacrifice its citizens unless it meant a swift and decisive victory for Ukraine.
North Koreans are fighting for Russia because their leadership wants food, energy, and missile technology from Russia. They aren’t there to win the war for Russia (they likely don’t even care about it).
NATO, on the other hand, doesn’t joke around. If they enter the war, it would be over in a few weeks.
Putin knows that. He wouldn’t have "invited" the 12,000 North Koreans if he thought it would provoke the West into taking an active role in the fighting.