The Divine Mr. M

In the military Doctrine of Force Concentration, it is stated that an attacker needs a Force Ratio of three to one over the defender. Ukraine's armed forces consists of 361,000 troops, so the Russians need over a million military personnel in order to secure its outcome. So far it seems the have only committed to 190,000. This is primary reason why they're being checked everywhere. Secondary considerations are the morale of the respective forces and Russia's so-so logistics.

~Two items first...

One: It seems that all the political leaders in Ukraine are kleptocrats of one type or another. And that Yanukovich, the leader who was most willing play ball with Putin, is also the most thuggish of the lot. Now that he has thoroughly screwed the pooch, Putin has to make the best of a pretty bad situation.

Two: Putin may be a son of a bitch, but he is neither stupid nor crazy, so forget all the Hitler analogies. The man is an ex-KGB colonel, meaning he is a ruthless pragmatist.

Okay, now for the 'mind reading'....

As the HQ of The Russian Black Sea Fleet, the Crimea is utterly non-negotiable for Russia. Now that it is back in Russian hands, they are not going to let it go. Hopefully the new leadership in Kyiv understands and is willing to swallow that shit sandwich. I'm not hopeful of that outcome, but one never knows.

Eastern Ukraine is a much dicier proposition. Putin probably hopes that they will except a few extra 'privileges' as ethnic Russians within Ukraine and not try for separation. These are the 'events on the ground' I have spoken of in the past few days.

If the majority Russian eastern provinces go for succession, then Putin is faced with two equally bad choices: A, let them hang out to dry and see how things turn out in a Ukrainian civil war or B, go in and help them, thereby becoming embroiled in said civil war.

The former would very bad for Putin domestically, abandoning fellow Russians to the 'fascist wolves'.

But the latter has the potential to become a suppurating nightmare.

Ethnic Ukrainians hate Hate HATE the Russians and so do the nations of Eastern Europe. Poland, which hates the Russians as much as the Ukrainians, shares a long border with Ukraine. I have little doubt that 'volunteers' and arms of all types would flood over said border if Russia intervened in a Ukrainian civil war. In all likelihood, they'll flow anyway. And there's lots of old Warsaw Pact gear floating around, so who could say where it came from.

I have said that such would be 'Yugoslavia writ large'. Think easily ten times as large, with ethnic cleansing and militia atrocities on a massive scale. I would not be surprised if the death toll reached over a million.

In addition, the gas lines to Europe would definitely be cut, both by accident and on purpose, and the EU's economy is rather shaky at the moment. A Ukrainian civil war would almost certainly cause another global economic meltdown and who knows where that would lead.

I'm fairly certain that Putin understands all of these factors and will do his best to tamp down passions in the eastern provinces. But these are The Bloodlands and history has shown us that in those lands the Worst Case is usually the most likely scenario.

Another Charming Thought: a Ukrainian civil war could destabilize Belarus.

EDIT: some maps to help visualize the situation.

http://www.nytimes.com/interactive/2014/02/27/world/europe/ukraine-divisions-crimea.html