Russia was literally invaded three times and lost millions upon millions of lives because the border with Ukraine is indefensible. That's why Napoleon invaded Russia through it. It's why the Third Reich invaded Russia through it. And it's why Russia's national security requires Ukraine to be a neutral country that NATO is not operational in. What NATO was doing in Ukraine absolutely justifies Russia's actions. NATO simulated an invasion of Kaliningrad with Ukraine. It flew B-52s in exercises in Ukraine. It was literally building and exercising it's logistics chain to establish nuclear first-strike capabilities. That's been clear since the early 90s when Clinton duplicitously told Russia Ukraine would remain neutral while asking his own generals to draft a plan to include Ukraine in NATO. This is literally the definition of Russian national security. Ukraine needed to remain neutral and establishing a nuclear transnational military presence unaccountable to any sovereign nation or any nation's people with an ambition of nuclear first strike capabilities lead by the USA that explicitly and publicly reserves the right for a nuclear first strike is exactly the opposite of remaining neutral.