To understand the Ukrainian invasion of Russia, we must understand certain facts about Russia. First, Russia is huge compared to Ukraine, 28.5 times larger, and has the largest land area of any country in the world. The Russians can afford to have the Ukrainians conquer a lot of Russian territory, while evacuating its civilians and pretending to fight. The Ukrainians will be stretched too thin after a while and their supply lines will be too long. It won't affect what is happening on the battlefield within Ukraine.
Second, Russia has a unique military history. They are experienced in giving up ground to buy time until fall and winter weather, with its rain, cold, snow, and ice makes roads impassible and invading armies ineffective. That is how Napoleon's army was defeated when it invaded Russia, and also what helped defeat Nazi Germany, aside from Hitler's insistence on overruling his generals.
Third, the Russian population is 3.5 times larger than Ukraine's population. Ukraine is running out of soldiers. The Russians can keep on throwing troops at Ukrainian soldiers to wear them out, and sustain high losses while doing so.
Ukraine's seizure of territory has embarrassed Putin to the extent that he has pulled some troops from Ukraine to fight the invasion and quell public unease. He has obtained 10,000 troops from North Korea and recruited naive Chinese to help fight the war with Ukraine because the numbers of Russian troops are limited. He has only recently called up a full scale conscription within Russia. Being conscripted to fight is never popular.
Russia has finally pushed out most Ukrainian troops from its territory. Putin does not like to lose, or give up on any prominent position he has taken, regardless of the cost to his nation.
We do know that the Russian banking sector raised interest rates to 21% near the end of October, 2024, and inflation was projected to average 8.8% for the year. And there have been reports that the Russian railway system is near breakdown because of a lack of ball bearings embargoed by the West, which will eventually be supplied by China.
Both the stress on Russia's economy and Ukraine's seizure of Russian territory are putting pressure on Putin to stop his ill-advised war. However, unless the invasion causes so much additional disruption that his generals seriously question the war, he may be able to keep pecking away at Ukraine for a long time.
Ukraine, meanwhile is suffering greatly from the war. Russia is gradually learning from its mistakes on the battlefield and getting better at using drones to kill Ukrainian troops and civilians. The war has degenerated into the use of missiles, drones, and artillery, with Russia destroying Ukrainian infrastructure, including the energy grid, and terrorizing civilians.
Ukraine's economic and manpower means are limited. If the United States drops its commitment to assist Ukraine, president Zelenskyy will have to concede some territory in the short term for peace. The European Union, shamefully, is still too weak militarily to provide sufficient weapons and ammunition to Ukraine.
The European Union still buys more in fuel, natural gas, and coal from Russia than it supplies to Ukraine in military and civilian aid. They know they need to turn that around, possibly using new nuclear plant designs for energy.