Ukraine

A lot of people either never saw or have forgotten the statements and clues that Russia does not plan to stop.

They've repeatedly said they want to take back the Baltic countries. That's why there's an American unit stationed there now. Invasion plans included Moldova. Every border country except Hungary has reported Russian attempts to create civil unrest.

It's obvious the Russians think they can avoid an article 5 declaration by having a country "voluntarily" leave NATO and join CSTO. This was in fact their plan for Ukraine, just with the EU instead. Their puppet got elected with massive amounts of misinformation, a vulnerable incumbent (his corruption was exposed), and promises to keep the country in the process of joining the EU. It was the reversal of joining the EU to instead sign treaties with Russia that triggered the Maidan. And then Putin reacted with Crimea and the Donbas region.

That's also part of a very old Russian playbook meant to keep countries from joining NATO. Because NATO doesn't allow countries to join if they have territorial disputes going on. That's why so many Eastern European countries have territorial disputes with Russian aligned separatists.