RealClearDefense has an analysis by Seth Cropsey of the motives and goals of both sides in the Russia-Ukraine war. It is one of the best I have seen, perhaps a “must read.”
Cropsey describes Russian aims in a way that explains why Putin acted as he did, and why he is unlikely to quit anytime soon. Ditto for those of Ukraine, which is also unlikely to quit. He believes the weak actors in the conflict are Germany, France, and possibly the U.S.
His conclusion is that Crimea is the real prize that both sides desperately need. He argues NATO needs to provide the arms necessary for Ukraine to meaningfully threaten to retake Crimea, if not to actually do so. And he describes why a Russia that includes what is now Ukraine becomes a global power center of nearly equal weight to China and the U.S., something it is worth our while to prevent.
