Ukraine & Georgia are 2 quite different things, but could become similar if the Ukrainians don't learn from Georgians mistakes.
Here's the short version:
Georgia has had a separatist issue since it got independence in 91.
Things eventually came to a head. Georgians went tit-for-tat with the separatists. One would mortar and snipe at the other, and each would blame the other for starting it on any given day. It went on for a decade. Ossetian police would should at Georgian police and the other way around. Georgia tried to assassinate Ossetian politicians, Ossetians struck back with car bombs. Eventually the Georgians snapped.
Russians, since they're not stupid, kept a close eye on the situation. With the growth of the FSB, they infiltrated the Georgian government. We monitor metadata, Russians go the cheaper, traditional route. They knew about the Georgian overreaction before it mobilized and warned Ossetians to evacuate. Some did.
The Georgians turned up with a battalion of heavy artillery and shelled civilians and separatists all the same. Here's what the BM-21 Grad company looked like firing: www.youtube.com
It was another 8 days before the Russians mobilized to put a stop to the fighting, pushed into Georgia, dismantled much of their military, then turned around and left just peacekeepers in Ossetia, and allegedly some encroachment in the West were Georgian troops simply fled after a token defense.
While this was going on, that idiot McCain was standing around saying "We're all Georgians now", because Georgia is a geopolitical ally that we willingly turned a blind eye towards as they shelled civilians, drastically damaging our regional credibility.