So what might convince Putin not to invade the Ukraine (again)?

Well, I have no idea what so ever. But either showing weakness or sending NATO troops to the Ukraine seem like mad alternatives which certainly will increase the risk of a Russian intervention.

I very, very much want to warn everyone against engaging in mirror-imaging:

Be Wary of Mirror Images.
One kind of assumption an analyst should always recognize and question is mirror-imaging--filling gaps in the analyst's own knowledge by assuming that the other side is likely to act in a certain way because that is how the US would act under similar circumstances. To say, "if I were a Russian intelligence officer ..." or "if I were running the Indian Government ..." is mirror-imaging. Analysts may have to do that when they do not know how the Russian intelligence officer or the Indian Government is really thinking. But mirror-imaging leads to dangerous assumptions, because people in other cultures do not think the way we do. The frequent assumption that they do is what Adm. David Jeremiah, after reviewing the Intelligence Community failure to predict India's nuclear weapons testing, termed the "everybody-thinks-like-us mind-set."69

Failure to understand that others perceive their national interests differently from the way we perceive those interests is a constant source of problems in intelligence analysis. In 1977, for example, the Intelligence Community was faced with evidence of what appeared to be a South African nuclear weapons test site. Many in the Intelligence Community, especially those least knowledgeable about South Africa, tended to dismiss this evidence on the grounds that "Pretoria would not want a nuclear weapon, because there is no enemy they could effectively use it on."70 The US perspective on what is in another country's national interest is usually irrelevant in intelligence analysis. Judgment must be based on how the other country perceives its national interest. If the analyst cannot gain insight into what the other country is thinking, mirror-imaging may be the only alternative, but analysts should never get caught putting much confidence in that kind of judgment.

We have a pretty good idea what military capabilities the Russians have in general (fast rearmament, but not done yet). Specifically on the Ukrainian border they have something like 4 mechanized brigades in the first echelong, and maybe another 6 mech brigades in the second echelong, 100 km back from the border. On top of this there should be a battalion of airborne guys (with their helos, including attack helos), and lots of Spetsnaz (special forces) running around, the latter very likely already inside the Ukraine. All units should be in full combat readiness, and at a peak level of training: a mix of professional soldiers and conscripts at the tail end of their service time. This is a very sizeable force!

However, while we have a good idea of the Russian capabilities, we have no idea what's happening inside Putin's head. I'm not sure what it's worth after all the caveats above, but I've been feeling much more worried in the last few days, nonetheless. So better buckle down folks.

Peak oil is not an energy crisis. It is a liquid fuel crisis.