One of the reasons the Russian advance had gone more slowly than Putin expected is that the Russians are having trouble getting food, fuel, and other support to their troops.They clearly lack the assets to maintain a reliable supply train. Poorly maintained trucks running on cheap, unreliable Chinese tires may be the undoing of their campaign. While the Russians may not be able to keep their soldiers fed, the Ukrainians are helping them stay warm by the fires of vehicles set alight by Javelins and Molotov cocktails.
Of course, the Russians may still pull off a costly win via overwhelming numbers, but the war in Ukraine shows the truth of the principle that amateurs study tactics and professionals study logistics.
The longer this goes, the worse it gets for Putin. He cannot afford to lose so he is likely to continue to escalate. But he is dangerously close to revealing that the Russian military is a paper tiger. He loses that way too. However, he may feel he wins by devastating Ukraine but that is likely to get them entrance into the EU.
The irony here is that before the Russian invasion, there was almost no chance Ukraine would ever be admitted to NATO. While that chance is still small, it may be greater than it was two weeks ago.