I'm not a huge fan of the Cato Institute, but this is a good piece:
Russia's military offensive against Ukraine is an act of aggression that will make already worrisome tensions between Nato and Moscow even more dangerous. The west’s new cold war with Russia has turned hot. Vladimir Putin bears primary responsibility for this latest development, but Nato’s arrogant, tone??deaf policy toward Russia over the past quarter??century deserves a large share as well. Analysts committed to a US foreign policy of realism and restraint have warned for more than a quarter??century that continuing to expand the most powerful military alliance in history toward another major power would not end well. The war in Ukraine provides definitive confirmation that it did not.
Thinking through the Ukraine crisis — the causes
“It would be extraordinarily difficult to expand Nato eastward without that action’s being viewed by Russia as unfriendly. Even the most modest schemes would bring the alliance to the borders of the old Soviet Union. Some of the more ambitious versions would have the alliance virtually surround the Russian Federation itself.” I wrote those words in 1994, in my book Beyond Nato: Staying Out of Europe’s Wars, at a time when expansion proposals merely constituted occasional speculation in foreign policy seminars in New York and Washington. I added that expansion “would constitute a needless provocation of Russia”.
What was not publicly known at the time was that Bill Clinton’s administration had already made the fateful decision the previous year to push for including some former Warsaw Pact countries in Nato. The administration would soon propose inviting Poland, the Czech Republic and Hungary to become members, and the US Senate approved adding those countries to the North Atlantic Treaty in 1998. It would be the first of several waves of membership expansion.