Russian leaders have evidently been shocked by Turkey's deliberate decision to shoot down one of their planes, which they say was motivated by Turkey's alleged support for Islamic State and greed for the proceeds of smuggled terrorist oil. A simpler explanation is that Russia would have done the same.

Here is the hypothetical: What would President Vladimir Putin do if civil war broke out in a neighboring country, which had been part of the Russian empire for centuries before breaking away under circumstances, and with borders, that Russians still found difficult to accept? What would he do if, in that war, some of the rebels were ethnic Russians at risk of being brutally crushed by the armed forces of the neighboring state?

Actually, that's not so hypothetical; it pretty much describes eastern Ukraine. And we know what Russia did — it became heavily involved in a poorly concealed invasion.