"Can anyone suggest a historical parallel to Russia's embarrassing showing in this war, now about to enter its second year? I'm not a military history buff, so I don't know."
Well, there's the first year of the war between Germany and Russia in World War II, but that's not entirely analogous. Russia wasn't the aggressor, and certainly wasn't perceived to be the stronger of the two forces.
Maybe Germany vs France/Britain after the end of the Phony War in 1940?
France was, at that time, considered to be the world's best military, and Germany comprehensively defeated it in a matter of weeks.
But this particular situation, in which the perceived larger, more capable military aggressor essentially crashed and burned after the initial thrust?
I can't think of anything quite like this at all until you roll back to the Persians dashing themselves to pieces against the Greeks a number of times in ancient history.
Vietnam and Afghanistan proved, in large part, the same point. The two largest, most capable militaries in the world at the time simply had no concept of how to fight against, or win against, what was essentially an asymmetrical guerilla war, where repeated massive application of force is essentially useless.
Both America and the USSR should have studied the British war against the Communist guerillas in Malay to see how to prosecute an asymmetrical war.