Spoke to ex uk forces guy yesterday. He said this is typical Russian tactics, throw the shit and conscripts in first to absorb and exhaust the anti tank ammo etc before rolling in the well trained and equipt troops.
I asked what the goals are likely to be and he said seizing a "horse shoe" in ukraine at least, so they have the ports (particularly sea ports).
Also having dealt with Russians, he gave examples I wont go into, but they do not care about the welfare of their troops. vast casualties are nothing to them.