A famous Russian tactic in war is "scorched earth", where the battleground is razed as they move past. This prevents the opponent from using the territory for shelter and resupply, and it is a tactic that proved successful for the Russian army both against Napoleon and Hitler.
Unfortunately for the Russian troops, Putin seems to have it all ass-backwards. The tactic is supposed to be employed during retreat, not when you advance. In the attack in eastern Ukraine, Russian forces are shelling the ground with artillery before their advance, which leaves them nothing but rubble to plant their flag on. This is devastating for them. Even though they are slowly gaining ground, it comes at a great cost, and it is a burden for them to move forward through crumbling ruins on destroyed roads. The Ukrainians, on their side, can retreat while staying in shelter in friendly territory. Of course, bombardment and constant fire causes heavy losses on the Ukrainian side, but the Russian losses are massive, reportedly several times larger, and their progress is slow.
Russia has entered a nightmare of their own making: a war of attrition where they are sending their troops to die by the hundreds or thousands for taking a worthless patch of dirt that used to have a village on it. Their resources were dwindling already, and now they are rapidly running out of cannon fodder. Ukraine has millions of brave people who are prepared to fight to defend their sovereignty, while Russia has less than 50,000 soldiers left, most of whom are exhausted, badly trained and unmotivated. This war might come to an end because Russia runs out of soldiers, and from the look of it, that moment might not be very far off.
