This is a war of attrition. The first side to run out of either:
- personnel
- weapons
- supplies (food, water, medical etc)
Loses the war.
It is as simple as that.
Even if successful in the current war in some sense, Russia will be unable to make good her losses in men and materiel or restore the economic ties with the West and the technological benefits that flowed from that relationship. This will lead to further demographic, economic, and military decline in Russia.
No, it’s not that simple.
Who would you say won the Vietnam War or American Revolution?
Both were long wars and the most powerful nation lost.
It really comes down to the political will of the people and their leaders.