A Buffer in Eastern Ukraine
In order of priority, Russia's position in eastern Ukraine comes first. Ukraine, from centuries past to today, forms the soft underbelly of the Russian state that must be insulated at all costs. If Ukraine comes under significant influence or control of a Western power, the Russian southwestern flank will be laid bare. But Russia is not strong enough to anchor itself on the Dnieper River and absorb both the military and economic costs of such an endeavor. So Russia must settle. The best Russia can do at this point is to try to consolidate autonomy for the eastern rebel provinces, using its tight grip over separatist commanders to dial up and down the conflict as the need arises. If Russia feels as though its demands are being ignored when it comes to NATO's buildup, sanctions or the like, violence in eastern Ukraine flares up. Once the Germans and the French get the message and start pressuring Kiev to make certain political concessions, the fighting quickly de-escalates.
This is a pattern that all sides are getting used to, but it is still far from ideal for Moscow. No matter what negotiations are in play, Russia is not about to withdraw its military foothold in eastern Ukraine. At the same time, that military dynamic provides the foundation for a pro-West Kiev to lean on the United States for help in defending itself against a persistent Russian threat. Russia must therefore carefully calibrate its military moves in eastern Ukraine, making clear that any Western push would risk a direct confrontation with the Russians, but also not going far enough to where its actions compel a U.S. response that could cause the Russian buffer to recede even more in the end.