What happens in the Donbas, however, offers Putin only a choice between different types of defeat.
If the battle reaches an autumn stalemate, he will have precious little to show for so much loss and pain. If the military momentum shifts and his forces get pushed back, even more so. And even if the Russians succeed in overrunning the whole of the Donbas and all across the south, they still have to hold those territories for the indefinite future in the face of several million Ukrainians who don't want them there.
Any significant Russian military success will likely create a major, open-ended insurgency that will get bigger for every district Russian forces may overrun. Putin went for broke in February with Plan A. The failure of that scheme means that plans B, C or any subsequent plans still leaves Russia going for broke - needing to suppress some or all of a very big country.
One way or another, Russia will have to keep fighting in Ukraine, either against the population, or against the Ukrainian army, and quite possibly both simultaneously. And as long as Kyiv sticks to its current line that demands Russian withdrawal before any concessions can be contemplated, there is not much Putin can do but carry grimly on.
https://www.bbc.com/news/world-europe-61348287