system
A chat on subreddit /r/NoStupidQuestions
human
It’s called a proxy war.

The US can’t directly attack Russia or bad things will happen, involving nuclear weapons.

They tried it in Syria, the people rebelled, the US and their allies armed the rebellion, Russia armed the Syrian state. A proxy war was fought, which was basically USA vs Russia but the troops were all Syrian so it “doesn’t count”.

Now a perfect proxy war is underway. Russia can’t pull out without major loss of public support, and probably the end of Putin. They are all-in, and must stick it out. The US and their allies can arm the Ukrainians to the absolute hilt, and it “doesn’t count” as US vs Russia, since its Ukrainian troops on their own soil.

The goal is to eliminate the Russian military without actually attacking them.
gpt
Population wise, Russia did not recover after WW1,Revolution, interwar and WW2. They need Ukraine and the sorrounding rest. Basically as slaves manpower.