I have little hope that Ukraine will end up surviving without major debilitating concessions. The sheer size of the Russian military means they just can't keep it up.
The sheer size of the Russian military may not be everything you think it is.
First, the current Russian military is a lot smaller than it used to be. Assuming it was ever even close to its Soviet-era on-paper size in the first place, which is dubious.
Second, Russia can only afford to commit a small fraction of its total military size to this conflict. It has to maintain security forces in other regions. It also has to maintain a credible deterrent force in the east, facing China. And it has to hold a substantial force in reserve, in case of NATO counterattacks and other contingencies.
Third, a larger military requires a larger industrial base and a larger logistics base. Having tons of troops doesn't mean much if you can't move them around or supply them with food and ammo. Having tons of tanks doesn't mean much if you can't keep them fueled and in good repair. Etc.
Fourth, guerrilla insurgencies are notorious for increasing an occupier's operational costs and draining their resources, while also reducing their efficiency and slowing their advance. The Russian military's size advantage is worth a lot more if it can bring its full weight to bear in a decisive battle against the smaller Ukrainian military. It's worth a lot less when Russia has to keep trickling troops into a guerrilla quagmire.
Right now it really seems like, for all its size advantage, the Russian military lacks the equipment, supplies, logistics, and morale to force the outcome they want. There's already talk of peace negotiations. A week in, and Putin's aggression is already slowing down.
The longer this drags on, the better Ukraine's chances are, I think.
