What did Russia just do? It had made an ambitious attempt to encircle a large are in Donbas and succeeded with the effort in just a few days. The Ukrainian army threw everything it had available into the cauldron and lost thousands of men while the Russian army avoided direct men against men fighting to minimize its own casualties. There is absolutely no reason to believe that the Russian forces are not able to repeat the process over and over.
[moonofalabama.org]
It looks like the same tactics Timoshenko used in Operation Bagration in 1944, AKA the Destruction of Army Group Center. Avoid direct battle, encircle the enemy and pulverize them with artillery while awaiting their surrender or starvation.