The will to defend your country proved to be a strong factor to be considered in many modern wars.
Sadly, this means unfortunately, that refugees have a short time window to get to safety. I see Russian troops getting to control border points of Ukraine so as to restrict incoming arms supplies.
Then there's the logistical implication of Russia, videos of heavy (if not extreme) ballistics are floating around.
I love rooting for the underdog but the line is getting thinner.
Russia certainly has the means to win all the battles, they might just then find they cannot keep the spoils.
In Ukraine, it seems there are more volunteers to fight than weapons.
Look how quickly the US-backed Afghan government fell when US troops retreated.
Another sad possibility is that Russia just wants to cause as much death, havoc and destruction, then retreat. But that seems a lot less like an achievement.
Most of the time that worked, the wars were at the end of a long supply chain (see Afghanistan for USSR, Vietnam for USA, Afghanistan and Iraq for USA) and were not felt to be vital (see protests over Vietnam).
In Ukraine, the war is next door to Russia and easily supplied. In addition, whatever it means to the Russian people, Putin has a lot staked personally on this war. In addition, Russia will be operating with a lot less restrictive rules of engagement (the invasion itself is a war crime, so adding other war crimes on top of it really is t going to change a whole lot of opinion for them).
Rather I predict this will be like the Boer War or the US war in the Philippines where despite spirited local defenses, the resistance is ground down.
Afghanistan being landlocked was more difficult to sustain a large mechanized military force.
3 to 1 attack ratio rule says there should be three times more attackers.
The morale hit is enormous. Especially when these kids are told they're sent there to liberate it from the Nazi government and they see people that look, talk and shit exactly like them. How long can they follow the orders and trust the chain of command? And how long can the internal propaganda convince the Russians that their war is not a senseless massacre of cousins and friends?
Russia has air superiority so that definitely upsets the balance, but so far they have not been able to use that very effectively. They did not even manage to protect their troop transport airplanes all that well, two of which got downed, and that really adds up in casualties.