I still don't get it, folks.
I know Russia's power projection is best when inside their country or in areas contiguous to Russia. As the attacker, you have the luxury of setting up and energizing your supply lines as far in advance as possible. Everyone in the military supply chain should have been on alert, pushing supplies to the front and getting more ready to go. Your applicable factories should have been alerted, wartime orders turned on, supplies coming out of warehouses and production lines ramped up. What is often done is determine the average numbers of miles/kilometers per day traveled by the various tracked and wheeled vehicles, factor in fuel consumption per mile/kilometer, and add in extra for poorly-tuned engines, etc. You also develop replacement factors for tires/lubricants/ammunition/food/water/clothing/general supplies/medical supplies/spare parts and have as much of those things as far front as possible, ready to support the attack. Railheads near Ukraine, both in Russia and in Belarus, should have been full of supplies and trucks, ready to go, possibly even trains on sidings. These concepts apply to any military, not just Russia. Logistics 101. Yet it doesn't seem Russia has done this well at all.
This is why what Putin hoped would be a blitzkrieg has turned into a grind once serious resistance began. Logistics wins wars.