For sure it's complicated. But the bottom line is that having the US military and NATO so close to Russia a nationality security threat to them and they will not tolerate it. The West's interference might look like it's helping Ukraine now with the supplying of weapons and supplies. But it's ultimately going to causing the absolute destruction of Ukraine.
The USA are using Ukraine as a pawn. Russia can not lose this war. They will sacrifice half of their men and destroy the whole of Ukraine before they let NATO set up base in Ukraine. The only way out this for Ukraine is negotiation, and Zelenski and the West have pretty much screwed that up.
Zelenski knows he can't win this war without the USA sending their troops in. But there is zero chance that Biden will do that.
Again this silly point. There are already NATO countries on Russia's borders for years. Right now there are large NATO forces in said member countries. Closer to both Moscow and St Petersburg than Ukraine is.
Geez. Do you really think NATO can get any closer to Moscow than it already is via Ukraine? That's a hard no. In no way at all can NATO get closer to Moscow without invading Russia. And we all know the invasions are going the other way. From Russia into its neighbours.
When will people hung up on Putin's NATO angle start internalising the implications of this very simple and thoroughly logical point? Fighting NATO expansion by invading Ukraine would be entirely symbolic by Russia. And you don't send tens of thousands of people to die for a symbolic point.
People should, in my opinion, get this through their skulls. Russia is there to grab strategic territories. At all cost. Be it human lives or suffering. Locally or globally. First and foremost. Like. 95% of it. That is what their actions speak of. The other 5% are minor goals and smoke and mirrors on a grand scale. The regions they are annexing is 100% consistent with a long running campaign to expand and dominate. Not even in the Eastern European context. But in the context of previous expansion in Asia going back decades, if not 100s of years. You can even clearly see it in a current map of Asia.
Soviet plan (dark lines) vs their current objectives (light lines).
Russia has wished to gain access to the Persian gulf since they found out about it. This is not idle speculation. It was the USSR's primary expansion objective in Asia. The blue was almost all part of the USSR, and the Soviets hardly made a secret of it. Easy to look up. But, they were stopped in Afghanistan. Sentiment from within Russia makes it clear they want all that back, but for now they're playing a slow game of pushing through and protecting (as per gaining control over Crimea and Eastern Ukraine) a corridor made up primarily at present by the Caucasus region between the black sea and the Caspian Sea. And strategic surrounding territories. Crimea and Eastern Ukraine are obvious targets within this context. When Russia talks about security concerns, then it is concern entirely relating this.
It's even possible to predict their next objectives based on this thesis.
Observe. The Caspian Basin Region of Kazakhstan. A mirror objective in relation to Eastern Ukraine and Crimea.
All to alleviate what they perceive as a strategic weakness in this corridor.
A concern of Moscow they have never made any secret of either.
In a decade or two after, if not sooner. The Russo-Iran war. With their sights on the Azerbaijani and other Occidental regions of Iran shown in yellow below (clearly Iran likes playing with fire, or are somewhat compromised already)
Only the assumption that this is still their primary goal explains their otherwise puzzling indifference to other NATO member states on their borders, closer to Moscow and St Petersburg, and near hysterical focus on Eastern Ukraine. Countering NATO expansion, in my opinion, is a big fat made up excuse.