Expanding on an earlier post.
Im not sure that Russia can win this militarily - as in completely conquering Ukraine. I think there was an assumption by pretty much everyone (especially the Russians) that this would be like either of the gulf wars - airstrikes would take out key infrastructure and any major defensive positions, tanks etc. The Urkanian air force would be wiped out. Their communications would be kaput. Then the massively superior Russian army roll in an most of the urkanians would judge they would rather live than fight.
But a week in and Kiev is still very much not captured, the Ukrainian government is very much still there with full communications, Russia has suffered heavy losses - its troops are less than enthusiastic, they have serious supply problems and they are mud bound.
Meanwhile the invasion - and the early successes - has prompted a wave of Ukrainian nationalist defiance and - crucially - hope. I definitely think the longer this goes on the worse it gets for Russia - sure they can take Kiev - (but its will take time and it will be gruesome) - but what about the rest of Ukraine? Its quite a hike to get the bulk of their Army (and their fuel and ammo and food) from Kiev in the north east to Lvov and Odessa - across country where every other road junction or bridge or village could have a couple of citizens militia waiting with western supplied weapons that can take out a main battle tank with one shot.
Ruasia's best hope was a blitzkreig style approach that toppled the regime, cowed the population and seriously disrupted organised defence - but that has failed. If anything the Ukrainian defence is more organised and adapting quickly - they see to have been much better prepared for this. They will also be getting not just western weapons (including things like night vision equipment which the Russians lack and will give them a real advantage) they will be getting high level NATO intelligence about enemy troop movements, supply dumps, plans etc.
The Russians will also have to occupy vast areas of very hostile country.
Also - in the age of moblile communications - the ukrianian government can organsie and meet online - they dont have to be in one place. If (when?
) Zelensky is taken out - they will have plans for who takes over.
Meanwhile they may have to deal with the effect of economic sanctions, growing unhappiness at home and an increasingly demoralised army.