As mentioned by Yogthos, Putin has decreed due to repeated use of long-range western weapons for terror attacks on civilians they need a buffer zone.

I think at this point the 3 eastern secessionist territories that have formally joined Russia are going to be part of Russia, that’s simple off the table. What Putin is now threatening is to seize more of the country. I believe he is doing this because it may actually be necessary and also in an attempt to give them something to bargain over with the west and the Ukraine in negotiations. Basically a threat, that they’ve already lost these territories and are not getting them back, that’s off the table but if they don’t come to the table, be reasonable, meet Russia’s original demands then they will lose a lot more but if they are willing to meet them Russia will almost certainly guarantee the territorial integrity of Ukraine minus the break-away regions part of Russia already legally and of course Crimea.

Things are getting interesting again because I read the EU money for $50billion of money for weapons and such for the Ukraine has cleared and honestly I do expect Biden to give the Republicans enough of a sweetheart deal on the border that they agree to his package for Ukraine. He might have to settle for a watered down version that only gives them enough funding to last through part of the rest of his term but I believe he’ll get them something even if he has to personally go to the Mexican border and bayonet a child on camera. Then again there is a chance, slim but growing that Trump pressures the congressional Republicans not to give him a thing because they want to use the border thing as a talking point for their base and giving him a win in any way waters down that talking point.