Being the advancing force has almost always been really hard and risky compared to being on the defensive and entrenched. There is a real risk that this war continues for many years to come with a battleline that moves back and forth a few kilometers with a few key points of interest trading hands back and forth. I think this won't really end because of what happens on the battlefield but because of what happens politically. How long can Putin sustain the war? How far are the Ukrainian people willing to go reclaim Donbas and Crimea? How many lives are they willing to sacrifice to reclaim what was lost?